JPH09198725A - Recording / reproducing method and recording / reproducing apparatus - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To realize a recording / reproducing method using a state of an atom or a molecule as a recording unit. A solid having a physical structure having an energy level structure composed of three or more energy levels is used as a recording medium, and the number of physical structures contained in the solid is N, i-th physical structure. Where the predetermined three levels of are the first, second and third levels, and h is Planck's constant, the energy of the first level is hω _i1 / 2π and the energy of the second level is hω _i2 / 2π, the energy of the third level is hω _i3 / 2
When π, | ω _i3 −ω _i1 | is ω _i31 , | ω _i3 −ω _i2 | is ω _i32 , and | ω _i2 −ω _i1 | is ω _i21 , (ω _i31 , ω _i32 ) is recorded on the recording medium by changing the distribution of (ω _i31 , ω
_The information is reproduced by detecting the distribution of _i32 ) or the distribution of ω _i21 .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording / reproducing method and a recording / reproducing apparatus in which the state of each atom or molecule is used as a recording unit.

[0002]

2. Description of the Related Art In the information society in recent years, a recording / reproducing method and a recording / reproducing apparatus based on the recording / reproducing method which have a recording density which is dramatically higher than the conventional one and which can cope with an ever-increasing amount of information are expected.

One of the limits of the recording density is an atom / molecule memory in which the state of each atom or molecule is used as a recording unit. In order to realize an atomic / molecular memory, technology for detecting and controlling phenomena at the atomic / molecular level is indispensable.

As an example of such technology, STM and A
FM or NSOM (Near using near field of light)
-Field Scanning Optical M
A large number of scanning probe technologies, such as microscope, are being studied, and the application to memory is actually being tried. However, at present, it has not been put to practical use due to technical problems such as the surface scanning speed being too slow.

On the other hand, with the progress of laser technology, research on new physical phenomena is progressing in the field of quantum electronics research targeting atomic gas. The representative is EI based on the coherent interaction between an atom and a laser.
T (Electromagnetically Induced Transparency) and L
WI (Lasing Without Inversion).

EIT and LWI are phenomena induced by irradiating an atomic system having both three levels with two laser beams to hold the atoms in a coherent state.

[0007] That is, EIT is a phenomenon in which the wavelength region where originally strong absorption should be transparent becomes transparent (JE Field et.
al., Phys. Rev. Lett. 67, 3062 (1991), K.-J. Moller et a
L., Phys. Rev. Lett. 66, 2593 (1991)). Also, LWI is
This is a phenomenon in which coherent light is not absorbed by using EIT and laser oscillation occurs even without population inversion (SEHarris, Phys. Rev. Lett. 62, 1033 (198).
9)).

EIT has already been verified in several atomic gas systems, and a large change in the permeability coefficient of several orders of magnitude has been reported. On the other hand, with respect to LWI, some experiments have been attempted in an atomic gas system and laser oscillation has not been achieved, but amplification of probe light has been realized (WEVeer et al., Phys. Rev. Lett. 70). , 3243 (1993)).

Applications using EIT and LWI include:
Optical filters that transmit only light in an extremely narrow band and lasers in the short wavelength region where it is difficult to form population inversion have been considered.

In addition to these, various new applications are considered to be possible. Considering the feasibility of such new applications, solid systems such as EIT and LWI are used instead of atomic gas systems. It is desirable to realize the phenomenon.

As an approach to solid-state systems, theoretical analysis has been conducted for impurities in semiconductor quantum wells, rubies and diamonds (Y.Zhu
et al., Phys. Rev. A49, 4016 (1994), D. Huang et al., JO
pt.Soc.Am.Bll, 2258 (1994), C.Wei et al., Phys.Rev.A5
1,1438 (1995)), no reports on experiments of EIT and LWI have been made on solid systems.

There are some points that must be taken into consideration in realizing EIT and LWI in a solid system, unlike the atomic gas system.

First, EIT and LWI basically have a closed three-level or four-level system, and it is essential that electrons do not escape to other levels under light irradiation. For this reason,
Even in the electronic state of the solid system, it is necessary to select a level such that the wave function is localized and relaxation to other levels does not easily occur.

As a candidate for a level satisfying such conditions, a physical property having atomic characteristics such as impurities such as transition metals and rare earths, point defects such as vacancies, and quantum structures such as quantum dots and quantum wires. Levels that can be said to be structural systems are mentioned.

The second point is that a solid system generally has a wide spectral width of optical transition. As the factors that determine the spectral width, the level involved in the transition is the uniform width caused by the temporal fluctuation of the energy value due to the interaction with the surroundings, and the temporal average value of the interaction There are two non-uniform widths due to the distribution of the levels themselves, depending on the level.

Among the solid-state systems, the physical structure systems described above have relatively small widths, but the uniform width and the non-uniform width are still large as compared with the atomic gas system. EIT
The characteristics of the LWI and LWI are determined by the resonance condition related to the frequency, and the size of the uniform width and the non-uniform width greatly affects the characteristics.

As described above, in order to realize EIT and LWI in a solid system, the above points must be taken into consideration. Therefore, in order to realize EIT and LWI in a solid system, an approach different from the atomic gas system is required. However, at present, the solid-state-specific approach necessary for realizing EIT and LWI in the solid-state has not been clarified.

Furthermore, in the case of a solid-state system, it is expected that the functions and features peculiar to the solid-state system and new EIT and LWI based on them will be applied, but such proposal has not been made so far.

[0019]

As described above, it is expected that a recording / reproducing method and a recording / reproducing apparatus capable of recording and reproducing information at the atomic / molecular level will appear.
The application to the ultra-high density recording by the scanning probe technique such as M, AFM, NSOM has been attempted, but at the present, the one for practical use has not been realized.

The present invention has been made in consideration of the above circumstances, and an object thereof is to record information in which the state of each individual atom or molecule is a recording unit and to record the same. / Providing a reproducing method and a recording / reproducing apparatus.

[0021]

[Means for Solving the Problems]

[Outline] In order to achieve the above object, a recording / reproducing method (claim 1) according to the present invention has a physical structure having an energy level structure composed of three or more energy levels as a recording medium. A solid is used, the number of the physical structures contained in the solid is N, the predetermined three levels of the i-th physical structure are the first, second and third levels, and h is Planck's constant, The energy of the first level is hω _i1 / 2π, the second level is
Hω the energy of the level _i2 / _2π, the third level of energy _{hω i3 / 2π, | ω i3} -ω i1 | the ω _i31, | ω
_{When i3} −ω _i2 | is ω _i32 and | ω _i2 −ω _i1 | is ω _i21 , information on the recording medium is changed by changing the distribution of (ω _i31 , ω _i32 ) in N physical structures. _Is recorded, and the distribution of (ω _i31 , ω _i32 ) or the distribution of ω _i21 is detected to reproduce the information.

Here, the physical structure means a quantum structure such as a quantum dot, a quantum wire or a quantum box, a crystal defect such as a point defect,
It means an impurity atom. Further, the number N of physical structures is the number of physical structures included in a portion irradiated with coherent light, and may be the number of physical structures included in the entire solid that is the object to be detected. It may be the number of physical structures included in the part.

To change the distribution, for example, the recording medium is irradiated with light or an electron beam, an electric field or a magnetic field is applied to the recording medium, or pressure is applied to the recording medium.

Another recording / reproducing method (Claim 2) according to the present invention is the same as the recording / reproducing method (Claim 1), wherein the maximum value of ω _i31 is ma in the N physical structures.
x (ω _i31 ), the minimum value is min (ω _i31 ), the maximum value of ω _i32 among the N physical structures is max (ω _i32 ), the minimum value is min (ω _i32 ), the first coherent light _Where ω _{p is} the angular frequency of ω _p and ω _c is the angular frequency of the second coherent light, min (ω _i31 ) <ω _p <max
(Ω _i31 ), min (ω _i32 ) <ω _c <max
Irradiating the recording medium with the first and second coherent light satisfying the condition of (ω _i32 ), absorbing the first coherent light in the recording medium, and
The information recorded in the recording medium is reproduced by measuring at least one of the fluorescence of the recording medium generated through the absorption of coherent light of a plurality of (ω _p , ω _c ) pairs. To do.

Another recording / reproducing method (claim 3) according to the present invention is the above recording / reproducing method (claim 1), wherein the maximum value of ω _i31 is ma among the N physical structures.
x (ω _i31 ), the minimum value is min (ω _i31 ), the maximum value of ω _i32 among the N physical structures is max (ω _i32 ), the minimum value is min (ω _i32 ), the first coherent light , Ω _p , the angular frequency of the second coherent light is ω _c ,
ω _p −ω _c is Δω, Δω is constant, and min (ω _i31 )
<Ω _p <max (ω _i31 ), min (ω _i32 ) <ω _c <
The absorption of the first coherent light in the recording medium when the first and the second coherent light satisfying the condition of max (ω _i32 ) is irradiated to the recording medium is I
_ab (ω _p ; ω _c ), I _lu (ω _p ; ω _c ) the fluorescence of the recording medium generated through the absorption of the first coherent light
Then, I _ab (Δω) = ∫I _ab (ω _p ; ω _p −Δ
ω) dω _p and I _lu (Δω) = ∫I _lu (ω _p ; ω _p −
Information recorded on the recording medium is reproduced by obtaining at least one of Δω) dω _p for a plurality of different Δω.

Another recording / reproducing method (Claim 4) according to the present invention is the same as the recording / reproducing method (Claim 1), wherein the solid has a structure when electrons are excited to its level. Has a fourth level that causes a change, the energy of this fourth level is hω _i4 / 2π, ω _i4 −ω _i1 | is ω _i41 ,
| Ω _i4 −ω _i2 | is ω _i42 , | ω _i4 −ω _i3 | is ω _i43 , and the maximum value of ω _i41 among the N physical structures is max (ω
_i41 ), the minimum value is min (ω _i41 ), the maximum value of ω _i42 among the N physical structures is max (ω _i42 ), the minimum value is min (ω _i42 ), among the N physical structures. The maximum value of ω _i43 is max (ω _i43 ), and the minimum value is min
(Ω _i43 ), where Ω _{p is} the Rabi frequency of the first coherent light and Ω _c is the Rabi frequency of the second coherent light, and when Ω _p <Ω _c , 1, the second coherent light, and min (ω
_i41) greater than max (ω _i41) smaller than the angular frequency or min (ω _i43) larger than the max, (ω
_i43 ) is irradiated with a third coherent light beam having an angular frequency smaller than _i43 ), and in the case of Ω _p > Ω _c , the recording medium is provided with the first and second coherent light beams, and mi.
angular frequency greater than n (ω _i42 ) and less than max (ω _i42 ) or ma greater than min (ω _i43 )
Information is recorded on the recording medium by irradiating a third coherent light having an angular frequency smaller than x (ω _i43 ).

Here, in order to efficiently change the distribution of (ω _i31 , ω _i32 ), and thus the distribution of ω _i21 , at the same time as the irradiation of the first, second and third coherent light, the electric field and the magnetic field are changed. It is better to apply the voltages at the same time.

Information may be reproduced as follows.

Min (ε _i31 ) <hω _p / 2π <max
_Under the condition of (ε _i31 ), the first coherent light is absorbed when the recording medium is irradiated with only the first coherent light, and the first coherent light is irradiated when the recording medium is irradiated with the first and second coherent light. Difference between the absorption of the first coherent light and the absorption of the first coherent light when the recording medium is irradiated with only the first coherent light and the first and second fluorescence of the recording medium. At least one of the fluorescence difference from the fluorescence of the recording medium generated through the absorption of the first coherent light when the coherent light is irradiated is measured for a plurality of (ω _p , ω _c ) pairs.

Here, among a plurality of (ω _p , ω _c ) pairs, ω
There are preferably two (ω _p , ω _c ) pairs whose absolute value of the difference in _c is less than or equal to the uniform width for the transition between the first and third levels.

In the recording / reproducing apparatus according to the present invention (claim 5), a solid having an energy level structure composed of three or more energy levels as a recording medium, and the first recording medium are provided. And an optical system for irradiating a second coherent light beam, wherein the optical system has the number of the physical structures contained in the solid as N and the predetermined three levels of the i-th physical structure as the third level. Using the first, second and third levels and h as Planck's constant, the energy of the first level is hω _i1 /
2π, the energy of the second level is hω _i2 / 2π, the energy of the third level is hω _i3 / 2π, | ω _i3 −ω _i1 |
_Is ω _i31 , | ω _i3 −ω _i2 | is ω _i32 , the maximum value of ω _i31 is max (ω _{i3 1} ) among the N physical structures, and the minimum of ω _i32 is N among the N physical structures. The value is min (ω _i32 ),
When the angular frequency of the first coherent light is ω _p and the angular frequency of the first coherent light is ω _c , min (ω
_i31 ) <ω _p <max (ω _i31 ) and min
It is characterized in that it has means for changing the angular frequencies of the first and second coherent light beams within a range satisfying the condition of (ω _i32 ) <ω _c <max (ω _i32 ).

Here, the physical structure means a quantum structure such as a quantum dot, a quantum wire or a quantum box, a crystal defect such as a point defect,
It means an impurity atom.

Another recording / reproducing apparatus according to the present invention (Claim 6) is the same as the recording / reproducing apparatus (Claim 5), wherein ω _p -ω _c is Δω. Δ
It is characterized in that it has means for changing the angular frequencies of the first and second coherent light under the condition that ω is constant.

Here, the number N of physical structures is the number of physical structures contained in the part irradiated with coherent light, and may be the number of physical structures contained in the whole solid which is the object to be detected. It may be the number of physical structures contained in a particular part of the solid.

Further, another recording / reproducing apparatus according to the present invention (claim 7) is the same as the recording / reproducing apparatus (claim 5), wherein the solid has a structure when electrons are excited to its level. The optical system has a fourth level that causes a change,
Let the energy of the fourth level be hω _i4 / 2π, ω _i4 −ω
_i1 | is ω _i41 , | ω _i4 − ω _i2 | is ω _i42 , | ω _i4 − ω _i3
| _Is ω _i43 , the maximum value of ω _i41 among the N physical structures is max (ω _i41 ), the minimum value is min (ω _i41 ), and the maximum value of ω _i42 is N among the N physical structures. max
(Ω _i42 ), the minimum value is min (ω _i42 ), the maximum value of ω _i43 among the N physical structures is max (ω _i43 ), the minimum value is min (ω _i43 ), and the first coherent light The Rabi frequency is Ω _p and the Rabi frequency of the second coherent light is Ω _c
And Ω _p <Ω _c , the first and second coherent light beams and mi on the recording medium.
Angular frequency greater than n (ω _i41 ) and less than max (ω _i41 ) or greater than min (ω _i43 ) max
When the third coherent light having an angular frequency smaller than (ω _i43 ) is irradiated and Ω _p > Ω _c , the recording medium is provided with the first and second coherent lights and m.
Angular frequency greater than in (ω _i42 ) and less than max (ω _i42 ) or m greater than min (ω _i43 ).
It is characterized in that it has means for irradiating a third coherent light having an angular frequency smaller than ax (ω _i43 ).

Another recording / reproducing apparatus according to the present invention (claim 8) is the recording / reproducing apparatus (claim 5 to claim 7), wherein the optical system is the first recording medium in the recording medium. It is characterized by having a means for measuring at least one of the absorption of one coherent light and the fluorescence of the recording medium generated through the absorption of the first coherent light.

Another recording / reproducing apparatus according to the present invention (Claim 8) is the recording / reproducing apparatus (Claims 5 to 7), wherein | ω _i2 −ω _i1 | is ω _i21 . Sometimes, the distribution of (ω _i31 , ω _i32 ) in the N physical structures is changed to record information on the recording medium, and
The distribution of _i31 , ω _i32 ) or the distribution of ω _i21 is detected to reproduce the information.

When the Rabi frequency is Ω _p and the Rabi frequency of the second coherent light is Ω _c , when Ω _p <Ω _c , the first and second coherent lights, and mi
Angular frequency greater than n (ω _i41 ) and less than max (ω _i41 ) or greater than min (ω _i43 ) max
Irradiating the recording medium with a third coherent light having an angular frequency smaller than (ω _i43 ), and when Ω _p > Ω _c , the first coherent light, the second coherent light, and mi
angular frequency greater than n (ω _i42 ) and less than max (ω _i42 ) or ma greater than min (ω _i43 )
It is characterized by comprising light irradiation means for irradiating the recording medium with a third coherent light having an angular frequency smaller than x (ω _i43 ).

In order to efficiently change the distribution of (ω _i31 , ω _i32 ), and thus the distribution of ω _i21 , the first,
It is preferable to apply the electric field and the magnetic field at the same time as the irradiation of the second and third coherent light.

Further, in the present invention, when the line width of the second coherent light is δω _c and the uniform width regarding the transition between the first level and the third level is ω _homo31 , δω _c
It is desirable to satisfy the condition of ≦ ω _homo31 .

[Operation] According to the present invention, by adopting a completely new recording / reproducing principle of utilizing the extremely high frequency resolution of the EIT phenomenon, each atom or molecule state is used as a recording unit. Recording / playback can be realized.

[0042]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) In the following description, the first embodiment will be described.
The level, the second level, and the third level (state vector) of are described as | i1>, | i2>, and | i3>, respectively.

Regarding the relationship between the three levels and light, as shown in FIG. 1, there are four types of excitation schemes (Energy Scheme). Hereinafter, the excitation type called Λ type shown in FIG. This will be explained as an example. In the case of Λ type, | i1> (| 1>), | i2> (| 2>), | i3> in order of increasing energy.
(| 3>).

In the case of the V type shown in FIG. 1 (b), contrary to the case of the Λ type, three levels are set in order of increasing energy | i1> (| 1>), | i2. > (| 2>), |
By setting i3> (| 3>), the same argument as in the case of Λ type is established.

In the case of the Ξ excitation type, as shown in FIG. 1C, the three levels are | i1> (| 1>) and | i3> (| 3 in order from the highest energy. >), | I2>
(| 2>), or as shown in FIG. 1 (d), | i1> (| 1>) in order from the lowest energy,
By setting | i3> (| 3>) and | i2> (| 2>), the same argument as in the case of the Λ type is established.

First, the EIT characteristic in which the number of physical structures is one will be described.

The EIT is composed of three levels related to a single physical structure and two laser beams connecting the levels. Λ
In the type, three levels are selected such that | i1> → | i3> and | i2> → | 3> are allowable transitions, and | 1> → | 2> are forbidden transitions.

The light that connects the ground states | 1> and | 3> is called probe light, and the light that connects the above two levels | 2> and | 3> is called coupling light. .

Further, the frequency ω _{p of the} probe light and | 1> →
| 3> Resonance frequency 2π corresponding to energy difference between levels
· Ε ₃₁ / h and the frequency difference [Delta] [omega _p of the frequency omega _c of coupling light | 2> → | 3> the frequency difference between the resonant frequency 2π · ε ₂₁ / h corresponding to the energy difference between the levels Let Δω _c .

The respective intensities are represented by Rabi frequencies Ωc and Ωp defined by the following equation.

Ωc = 2π <3 | μ · E | 2> / h (1 ₁ ) Ωp = 2π <3 | μ · E | 1> / h (1 ₂ ) where μ is an operator related to the dipole moment, E is an operator related to the electric field.

Next, let us consider a state in which the lower two levels as shown in the following equation are crossed at each Ravi frequency to form a linear combination.

* +> = (Ωc | 1> + Ωp | 2>) / (Ωc ² + Ωp ² ) ^1/2 (2 ₁ ) *-> = (Ωc | 1> −Ωp | 2>) / (Ωc ² + Ωp ² ) ^1/2 (2 ₂ ) where detuning of two laser beams (detuni
ng) are equal, that is, Δω _c = Δω _p , the population of the three-level system
Considering the time change of, it is easily shown that the population of *-> never increases or decreases.

Therefore, in the steady state, the probability of occupying the *-> level is 1. This is a phenomenon called population trapping.
At this time, regarding the transition dipole moment between *-> and | 3>, <3 | μ · E |-> = (h / 2π) (Ωc · Ωp−Ωp · Ωc) (3) / ( ^{Ωc 2 + Ωp 2) 1/2)} = 0 strictly zero, absorption does not occur. This is EIT
It is. As the physical origin that absorption does not occur,
>>, it can be considered that the transitions of | 1> → | 3> and | 2> → | 3> are canceled by the interference effect.

As is clear from the equations (2 ₁ ) and (2 ₂ ), the level to be trapped, |->, is
Regarding | 1> and | 2>, it is configured by the Ravi frequency, that is, the ratio of the light intensity. Therefore, the property of |-> can be changed by changing the light intensity.

If Ωc >> Ωp, then |->-| 1
>, That is, trapped in a state close to the ground state. Conversely, when Ωc << Ωp, the state is trapped in a state close to the lower excited state | 2>.

From | 1> to | 3 when EIT is occurring
As shown in FIG. 2, the shape of the absorption spectrum for> has an absorption hole, that is, a transparent region, at the position of ω _p satisfying the condition of Δω _p = Δω _c .

When Δω _c = 0, as shown in FIG. 2A, Δω _p = 0, that is, a hole is formed at the center of the absorption spectrum.

When Δω _c ≠ 0, as shown in FIG. 2 (b), a hole is formed in the region at the bottom of the absorption.

The width of the hole depends on the Rabi frequency Ω of the coupling light.
is almost equal to c. Therefore, the width of the hole can be controlled by changing the intensity of the coupling light.

Next, when there are a plurality of physical structures (when there are N)
The EIT characteristic of will be described.

As mentioned above, the uniform width and the nonuniform width are wider in the solid system than in the atomic gas system. Therefore, the spectrum of the solid system is a very wide spectrum in which the spectra of individual physical structures spread by a uniform width are distributed by overlapping the central positions thereof. In this situation,
The same applies not only to the transition of 1> → | 3>, but also to the transition of | 2> → | 3>.

Therefore, as in the EIT experiment performed in the atomic gas system, the EIT signal observed with ω _c fixed is _detuning because of the (ε _i31 , ε _i32 ) distribution. The number of physical structures that meet the EIT condition that the two are equal is small, resulting in an extremely small signal as shown in FIG.

Not only that, but the characteristics such as where one physical structure contributes to the EIT characteristics of the entire system are not so clear. Therefore, so far, the EIT characteristic of each physical structure appearing in the absorption characteristic of ω _p on the ω _p axis is not only difficult to detect, but the method for controlling it is not clear, and some application is considered. It seems difficult to go.

The principle underlying the recording / reproducing at the single physical structure (molecule / atom) level of the present invention is (ω _p , ω _c ).
This is to consider the change in the absorption characteristic of ω _p on the plane. As a result, as described below, it is possible not only to detect the EIT characteristic of the physical structure, but also to change the EIT characteristic (ε _i31 , ε _i32 ) distribution of each physical structure, and at the single physical structure level. Recording / playback is possible.

First, let us consider one physical structure. | 1
Regarding the absorption of ω _p into> → | 3>, the change amount when the frequency ω _{c of the} coupling light is changed is (ω _p , ω _c ).
Think on a plane.

FIG. 4 shows the characteristics under the condition of Ωp <Ωc <(uniform width). The phenomenon itself that appears in the spectrum is quite simple. As shown in FIG. 4A, naturally, an absorption spectrum of one physical structure is obtained by cutting along the plane of ω _c = const.

The condition under which EIT occurs is Δω _p = Δω _c , and (ω _p = ω ₃₁ = 2πε ₃₁ / h, ω _c = ω ₃₂ = 2πε
₃₂ / h) on the line that forms an angle of 45 degrees with the ω _p axis.

FIG. 4B shows the spectrum viewed from the direction of 45 degrees, and it can be seen that a narrow hole corresponding to the Rabi frequency of the coupling light is opened.

If only this hole portion is extracted, FIG.
As shown in (c), it can be seen that the absorption spectrum of a single physical structure is rotated by 45 degrees, and the thickness is a thin plate-like spectrum having a Rabi frequency.

Next, consider the case where there are a plurality of physical structures. Each physical structure is a thin plate-shaped absorption hole created by EIT.
It occurs around the point (ω _i31 (i), ω _i32 (i)) corresponding to the energy between levels of each physical structure on the (ω _p , ω _c ) plane.

In the solid system, the nonuniform width is wide, and ω _i31 (i)
And ω _i32 (i) are distributed on the ω _p and ω _c axes, respectively.
Therefore, if the Rabi frequency is reduced and the thickness of each plate is reduced, the contribution of each physical structure becomes (ω
It is possible to completely separate them on the _p , ω _c ) plane.

Thus, ω on the (ω _p , ω _c ) plane
Considering the change in absorption characteristics of _p , absorption holes due to each physical structure appear separately for each physical structure, and the center position is (ω _i31 (i), ω _i32 (i)) That is the point.

Therefore, by observing the EIT signal of the entire system on the (ω _p , ω _c ) plane and examining where the plate-like holes appearing in absorption appear, the energies ε _i31 and ε _{i32 of} each physical structure are _obtained . You will know the position of.

Therefore, when the distribution of (ω _i31 , ω _i32 ) in the N physical structures is changed by, for example, laser irradiation and information is recorded on the recording medium, (ω _i31 , ω _i32 ) of If you detect the distribution,
Information can be reproduced.

Here, as shown in FIGS. 4 and 5, (ω
_In order to detect the absorption characteristic of ω _p on the _p , ω _c ) plane, it is indispensable to measure the absorption of ω _p for a plurality of ω _c . That is, it is preferable to reproduce the information recorded on the recording medium by measuring the absorption characteristics for a plurality of (ω _p , ω _c ) pairs.

The reason for this is that when the absorption of ω _p is measured with respect to a single ω _c = ω _c ⁰ , the absorption characteristics as shown in FIGS. 4 and 5 are given by ω _c = ω _c ⁰ (= const. ), The spectrum has the shape of the cross section cut by the plane,
This is _because , among the physical structures in which the energies ε _i31 and ε _i32 are distributed over a wide range, the absorption holes may be detected only for the physical structures that satisfy the relationship of 2πε _{i32 to} hω _c ⁰ .

Further, even if the relationship of 2πε _{i32 to} hω _c ⁰ is satisfied, if the extreme value of the absorption hole does not exist on the ω _c = ω _c ⁰ plane, the signal corresponding to the absorption hole is extremely weak. It is difficult to identify the position of the hole.

With respect to the set value of ω _c ⁰ , ω _c = ω _c
Including the extreme value of the absorption hole on ⁰ is stochastic.
This also eliminates the single omega _c, a plurality of omega _c, measuring the absorption of omega _p is, with respect to the physical structure population energetically distribution, absorption hole in due to individual physical structure It turns out that it is an indispensable element for detecting.

Since the absorption holes shown in FIGS. 4 and 5 are obtained by rotating the absorption spectrum of a single physical structure by 45 degrees, they are parallel to the longitudinal direction, that is, ω _c = ω _p + const. The width in the direction is about the uniform width of a single physical structure spectrum.

Therefore, in order to detect the holes of each absorption, not only the line width of the coherent light corresponding to ω _p but also the
It is desirable that the line width of coherent light corresponding to ω _c is also equal to or less than the uniform width.

Further, it is desirable that not only the interval of ω _p at the time of measurement is equal to or less than the uniform width, but also each interval of a plurality of ω _c is equal to or less than the uniform width. .

(Second Embodiment) In the (ω _p , ω _c ) plane, it is also possible to individually detect absorption holes relating to ω _{p and} to detect the following integrated intensity of absorption in the present invention. It is an important means for reproducing the information recorded on the recording medium. Now, consider the integration of I _ab (Δω) = ∫I _ab (ω _p ; ω _p −Δω) dω _p under the condition that the value of (ω _p −ω _c ) = Δω is constant.

First, the characteristics in the case of one physical structure will be described. This I _ab (Δω) is obtained by integrating I _ab (ω _p ; ω _c ) in a direction forming 45 degrees with the ω _p axis on the (ω _p , ω _c ) plane.

FIG. 6 shows the distribution of I _ab (Δω). FIG.
A narrow hole with a width Ω _c corresponding to the hole in (b) is Δω = ω ₃₁ −
It can be seen that it is near ω ₃₂ = ω ₂₁ ) and has a constant value in other regions. This constant value is the integrated intensity of absorption of one physical structure, which is a physical quantity specific to the physical structure, I ₀ = ∫I
Matches ⁰ _ab (ω _p ) dω _p .

FIG. 7 shows I _ab (ω _p ; ω) when the temperature is changed.
_c ) and ΔI _ab (ω _p ; ω _c ) are shown.
From FIG. 7, it can be seen that as the temperature rises, I _ab (ω _p ; ω _c ) and ΔI _ab (ω _p ; ω _c ) extend in the direction of 45 degrees as a whole, but I _ab (Δω) does not change at all.

8 (a) and 8 (b) show the distribution of I _ab (Δω) and ΔI when there are a plurality of physical structures, respectively.
The distribution of _ab (Δω) is shown. I _ab (Δω) has a hole with NI ₀ as a baseline and a depth and width Ω _c that is an integral multiple of I ₀ . ΔI _ab (Δ in FIG. 8B
The distribution of ω) corresponds to the inverted sign of only the hole portion.

The integer value obtained by dividing the height and depth of these rod-shaped spectra by I ₀ is ω on the Δω axis.
_It means the number of physical structures whose value of ₂₁ is equal to its Δω. Also in this case, I _ab (Δω) and ΔI
It goes without saying that _ab (Δω) does not depend on temperature.

From the above, I _ab (Δω) and ΔI
_{If ab} (Δω) is measured and used for reproduction of information recorded on the recording medium, extremely stable reproduction of information that does not depend on temperature can be performed.

Further, I _ab (ω _p ; ω _c ) or ΔI _ab
When (ω _p ; ω _c ) is used for reproducing information,
The distribution of (ω _i31 , ω _i32 ) can be reproduced at the single physical structure level, whereas I _ab (Δω) and ΔI _ab
When (Δω) is used for reproducing information, it is possible to reproduce the distribution of ω _{i21 at} a single physical structure level.

It should be noted that not only absorption but also light emission is I _lu (Δω) = ∫I _lu (ω _p ; ω _p −Δω) dω _p or I _lu (Δω) = ∫ {I ⁰ _lu (ω _p ) − I _lu (ω _p ； ω _p
Similar effects are obtained when information is reproduced by measuring −Δω)} dω _p .

(Third Embodiment) Recording of information will be described below.

In the present invention, information is recorded on the recording medium by changing the energy level distribution of the physical structure in the (ω _p , ω _c ) plane.

In order to change the energy level distribution, for example, the recording medium is irradiated with light or an electron beam, an electric field or a magnetic field is applied to the recording medium, or a pressure is applied to the recording medium. It suffices to excite a part of the group and change its energy level.

In particular, in order to record information at a single physical structure level (molecule / atom level), the present invention uses the above-mentioned population _trapping , and the distribution of (ω _i31 , ω _i32 ) or ω _i21 Transform the distribution of at the single physical structure level.

Specifically, as in the case of reproduction, the recording medium is simultaneously irradiated with the first and second coherent light beams having angular frequencies ω _p and ω _c and Rabi frequencies Ω _p and Ω _c . , In a state where a certain physical structure is subjected to population trapping, and further when an electron is excited, a structure change occurs, or an electron is ionized from its level, to excite to | i4>, Third of angular frequency ω _ex
The coherent light of is also irradiated by, for example, a laser.

The physical structure that changes the state by such a method will be described with reference to the drawings. (Ω _p , ω
_c ) In the plane, the population trap by the irradiation of the first and second coherent light beams has a line (ω _i31 , on the line of 45 degrees around the point (ω _p , ω _c ), as shown in FIG. The physical structure with ω _i32 ) occurs.

Here, when Ω _p <Ω _c , the physical structure is trapped in the state of | i1>. Therefore, as shown in FIG.
By irradiation with the third coherent light having the angular frequency ω _ex that causes the transition between | i1> and | i4>, the physical structure satisfying ω _ex = ω _i41 is selectively excited to | i4>. Is
Causes ionization and structural changes. Then, by irradiating a plurality of third coherent light beams having different angular frequencies ω _ex , it is possible to make holes in the distribution of (ω _i31 , ω _i32 ) as shown in FIG. 11.

When Ω _p > Ω _c , the physical structure is trapped in the state of | i2>. Therefore, by irradiation with the third coherent light L having an angular frequency ω _ex that causes a transition between | i2> and | i4> as shown in FIG. 12, a physical structure satisfying ω _ex = ω _i24 is obtained. , Is selectively excited to | i4>,
Causes ionization and structural changes. And even in this case,
By irradiating a plurality of third coherent light beams having different angular frequencies ω _ex , (ω _i31 , ω
_i32 ) can be punctured in the distribution.

It is also possible to selectively cause a state change even in a physical structure in which a population trap has not occurred.

FIG. 13 shows the distribution of the physical structure which is excited to | i3> under the irradiation of the first and second coherent light without causing a population trap and absorbing the first coherent light. Indicates.

Therefore, as shown in FIG. 14, | i3
By irradiation with the third coherent light having an angular frequency ω _ex that causes a transition between> and | i4>, a physical structure satisfying ω _ex = ω _i34 is selectively excited to | i4>,
Causes ionization and structural changes. And even in this case,
Preferably, by irradiating a plurality of third coherent light beams having different angular frequencies ω _ex , as in the case of FIG.
You can make a hole in the distribution of (ω _i31 , ω _i32 ).

When recording information by changing the distribution of (ω _i31 , ω _i32 ) over a wide range, the same operation may be performed on a plurality of values of (ω _p , ω _c ).

Further, by simultaneously applying the voltage and the magnetic field together with the irradiation of the first, second and third coherent light, the energy level of each physical structure changes,
The values of ω _i31 , ω _i32 , ω _i41, etc. change.

Therefore, it is possible to change the distribution of (ω _i31 , ω _i32 ) without changing the values of (ω _p , ω _c ), which enables efficient recording of information.

(Fourth Embodiment) In this embodiment, a YAG crystal containing 0.1 mol% of Eu as an impurity is used as a recording medium.

FIG. 15 shows the energy level of Eu.
The ground state of Eu is ⁷ F ₀ , 18950 cm from ⁷ F ₀
^-1 There is an excited state of ⁵ D ₁ on the high energy side, ⁷ F
_A strong optical transition occurs between ₀ and.

There is an excited state of ⁷ F ₁ from ⁷ F ₀ to 460 cm ^{−1 on the} high energy side, and a strong optical transition occurs with ⁵ D ₁ . In addition, ⁷ F ₀ to 36000c
A charge transfer state continuously exists near the high energy side of m ^{-1 to} 42000 cm ^-1, and the Eu atom in which electrons are excited changes its valence from +3 valence to +2 valence.

This recording medium is put in a temperature-variable cryostat having an optical window whose visible range is transparent, and the sample temperature is kept at 4K by cooling with liquid helium. In this state, the recording medium is irradiated with two ring dye lasers excited by an argon ion laser. As a laser dye for driving the two ring dye lasers, coumarin having a tuning range of 17240 to 19230 cm ⁻¹ is used.

Here, the oscillation line width of the ring dye laser is adjusted to be 500 kHz = 0.000017 cm ⁻¹ . Also, one of the ring dye lasers (L
1) shows that the oscillation frequency ω _p is around 18950 cm ⁻¹ ,
The other (L2) has an oscillation frequency ω _c of 18490c.
Adjust so as to sweep near m ^-1 . As for the laser light intensity, the Rabi frequency of lasers L1 and L2 is 3 MH
z and 17 MHz are set.

First, the energy distribution of Eu before recording information on the recording medium was detected by the following method. That is, the information recorded before the new information was recorded on the recording medium was reproduced by the following method.

First, the laser L2 was not irradiated, and the oscillation frequency of the laser L1 was changed from 1945.0000 cm ⁻¹ to 1
The absorption spectrum, I ⁰ _ab (ω _p ) of the laser L1 is detected by continuously changing it to 895.50000 cm ⁻¹ .

Next, the oscillation frequency of the laser L2 is set to 1848.
Fixed to 5.0000cm ^-1, the oscillation frequency of the laser L1 from 18945.0000cm ^-1 18955.00
The absorption spectrum of the laser L1, I _ab (ω _p ; ω _c ), is continuously changed to 00 cm ⁻¹ , and I ⁰ _ab (ω
_p ), ΔI _ab (ω _p ; ω _c ) = I ⁰ _ab (ω _p ) −
_Find I _ab (ω _p ; ω _c ).

Next, the oscillation frequency of the laser L2 is set to 0.00
02cm fixed to ^{-1 18485.0002cm -1} increases, 18,945.00 the oscillation frequency of the laser L1 again
The absorption spectrum of the laser L1 is changed from 00 cm ⁻¹ to 18955.00000 cm ⁻¹ continuously, and I _ab (ω
_p ; ω _c ) is detected to obtain ΔI _ab (ω _p ; ω _c ).

In this way, the oscillation frequency of the laser L2 is sequentially increased by 0.0002 cm ⁻¹ and the laser L is increased each time.
The process of detecting the absorption spectrum of
Continue until the oscillation frequency of 2 becomes 18495.0000 cm ^-1 .

FIG. 16 shows ΔI _ab thus obtained.
Part of (ω _p ; ω _c ) is the oscillation frequency ω of the laser L1.
It is shown in the (ω _p , ω _c ) plane with _p and the oscillation frequency ω _c of the laser L2 as two coordinate axes. From FIG. 16, it can be seen that absorption holes associated with the EIT of each pseudo atom (physical structure) are observed.

FIG. 17 shows that the value of Δω = ω _p −ω _c is 12
Setting for each MHz = 0.004 cm ⁻¹ , ΔI _ab (Δω) = ∫ {I ⁰ _ab (ω _p ) −I _ab (ω _p ; ω)
The integrated intensity of _p− Δω)} dω _p is obtained for each Δω.
It was observed that the value of ΔI _ab (Δω) was an integral multiple of a certain fixed value.

Next, the case of recording new information on this recording medium will be described.

In order to record information, lasers L1 and L2 whose Rabi frequencies are set to 17 MHz and 3 MHz, respectively.
And another ring dye laser L3 (oscillation frequency ω _ex ) are prepared, and the output light of coumarin dye excitation is applied to the BBO crystal.
Irradiate the recording medium with the harmonic wave.

Recording of information was sequentially performed under the following conditions.

(1) ω _p = 18952.0020c
m ^-1 , ω _c = 18486.0000 cm ^-1 , ω _ex = 38
000-40,000 cm ⁻¹ (2) ω _p = 18952.0000 cm ⁻¹ , ω _c = 18
486.0020 cm ^-1 , ω _ex = 40000-4200
0 cm ⁻¹ (3) ω _p = 18952.0000 cm ⁻¹ , ω _c = 18
486.0120 cm ^-1 , ω _ex = 38000-4000
0 cm ⁻¹ FIGS. 18, 19, and 20 are (1) to (3), respectively.
After each of the procedures, the irradiation of the laser L3 is stopped, the lasers L1 and L2 whose Rabi frequencies are reset to 3 MHz and 17 MHz are irradiated, and ΔI _ab (ω _p ; ω _c ) is measured.

As can be seen from a comparison with FIG. 16, some of the absorption holes of each physical structure disappear in the direction of 45 ° with the values of ω _p and ω _c used for recording. You can see that It can also be seen that the information recorded up to that point does not change even if new recording is performed.

FIG. 21 shows the measured Δ after the procedure of (3).
It is the result of I _ab (Δω).

As can be seen from FIG. 21, Δω = 465.
The ^value of ΔI _ab (Δω) at 9880 cm ⁻¹ is 5 to 2
To ΔI _ab (Δ) at Δω = 465.98080 cm ⁻¹
The value of ω) changes from 5 to 1, and Δω = 466.0020.
The ^value of ΔI _ab (Δω) at cm ⁻¹ changed from 4 to 1.

When the sample temperature was raised to room temperature and this ΔI _ab (Δω) was measured again, the same measurement result as in FIG. 21 was obtained, and ΔI _ab (Δω) was used as the recording data. The stability of the morphological recording method with respect to temperature was confirmed.

(Fifth Embodiment) As in the case of the fourth embodiment, YA containing 0.01 mol% of Eu as an impurity.
G crystals were used as a recording medium. However, in this embodiment,
Au is vapor-deposited on the two side surfaces of the YAG crystal to form electrodes. This electrode is for applying an electric field as an external field to the recording medium.

In this embodiment, information is recorded on the recording medium as follows.

That is, the angular frequency ω _p is 1 on the recording medium.
Laser L1 fixed at 8952.0020 cm ⁻¹ ,
In a state where the angular frequency omega _c is irradiated with laser L2 fixed to 18486.0000Cm ^-1, the recording medium, the angular frequency omega _ex in 1 minute irradiates the laser 3L which is swept from 38000 to 40000cm ^-1. Also, the electrodes are
A voltage obtained by sweeping a triangular wave between 0 V and 5 V at 1 Hz is applied.

22 and 23 are views showing changes in ΔI _ab (Δω) before and after recording, respectively.

In the first embodiment, when the value of Δω is equal to the difference between the angular frequency ω _p and the angular frequency ω _c , ΔI
_Although the value of _ab (Δω) was changed and recording was performed, in the present embodiment, the value of ΔI _ab (Δω) is changed not only at Δω = 465.98080 cm ⁻¹ but also in a wider range. .

This is because even if the values of the angular frequencies ω _p and ω _c are fixed, the energy level of each physical structure changes due to the electric field, and the physical structure satisfying the conditions of the population trap changes due to each electric field. As a result, the number of physical structures excited to | i4> has increased. As described above, it was confirmed that information can be efficiently recorded on the recording medium by using the electric field.

In the present embodiment, the case of an electric field as the external field has been described. However, in the case of other external fields such as a magnetic field, temperature, pressure, etc., the change of the optical spectrum of each physical structure is similarly changed. Can be detected.

(Sixth Embodiment) In this embodiment, Eu is used as an impurity as in the fourth and fifth embodiments.
YAG crystal containing 0.1 mol% of is used as a recording medium. A feature of this embodiment is that the recorded information is reproduced by measuring fluorescence instead of absorbing light.

[0135] recording medium of the present embodiment, as shown in FIG. 24, from ⁵ D ₁ of about 2415cm ^-1 higher energy side ⁵
There is an excited state called D ₂ , and when the electron transits from this state to ⁷ F _0, it exhibits strong fluorescence with a wave number of about 21360 cm ⁻¹ .

Therefore, with respect to the Eu atom excited to ⁵ D ₁ without being population trapped, Pb _1-x Cd _x S or PbS that oscillates infrared rays in the vicinity of 2300 to 2500 cm ^-1 as the third coherent light.
Selectively ⁵ D by using a semiconductor laser of the _1-x Se _x
If excited to ₂ , it is possible to detect the fluorescence when excited to ⁷ F ₀ .

Here, the same first and second coherent light beams as in the fourth embodiment are used, and as the third coherent light beam, the peak frequency of the oscillation frequency is 2 in particular.
411 cm ^-1 , PbS _1-x S with a Rabi frequency of 0.2 MHz
using a semiconductor laser L3 of e _x, it was performed by the following method to detect the energy distribution of Eu before information is recorded on the recording medium. That is, the information recorded before the new information was recorded on the recording medium was reproduced by the following method.

First, with the laser L2 not being irradiated and the laser L3 being irradiated, the oscillation frequency of the laser L1 is set to 1
8945.000 cm ^-1 to 18955.0000c
21000 observed when continuously changed up to m ^-1
The fluorescence intensity I ⁰ _lu (ω _p ) with a wave number of cm ⁻¹ or more is detected using a filter and a photo counter.

Next, the oscillation frequency of the laser L2 is set to 1848.
With the laser L3 fixed at 5.000 cm ⁻¹ and irradiated with the laser L3, the oscillation frequency of the laser L1 is 18945.00.
Fluorescence intensity I _lu (ω _p ; ω _c ) with a wave number of 21000 cm ⁻¹ or more, which was observed when continuously changing from 00 cm ⁻¹ to 18955.00000 cm ^−1, was detected, and the fluorescence intensity I was detected.
Difference from ⁰ _lu (ω _p ), ΔI _lu (ω _p ； ω _c ) = I
⁰ _lu (ω _p ) −I _lu (ω _p ; ω _c ) is _calculated .

Next, the oscillation frequency of the laser L2 is set to 0.00
02cm ^-1 is increased, in the state fixed to 18485.0002Cm ^-1, laser L3 is irradiated, the oscillation frequency of the laser L1 from 18945.0000cm ^-1 1895
Of 21000Cm ^-1 or more wave number observed when the continuously changed to _{^{5.0000cm -1 I lu (ω p;}} ω c)
_Is detected and ΔI _lu (ω _p ; ω _c ) is obtained.

In this way, the oscillation frequency of the laser L2 is sequentially increased by 0.0002 cm ^-1 , and the emission intensity I is increased each time.
_The process of detecting _lu (ω _p ; ω _c ) and _obtaining ΔI _lu (ω _p ; ω _c ) when the oscillation frequency of the laser L2 is 1849
Continue until it reaches 5.0000 cm ^-1 .

FIG. 25 shows the ΔI _lu thus obtained.
Part of (ω _p ; ω _c ) is the oscillation frequency ω of the laser L1.
It is shown in the (ω _p , ω _c ) plane with _p and the oscillation frequency ω _c of the laser L2 as two coordinate axes. As with FIG. 16, it can be seen that fluorescent holes associated with the EIT of each pseudo atom (physical structure) are observed.

However, the difference from FIG. 16 is that the number of holes is small. This is the line width of the laser L3 is, ⁵ D
Narrower than inhomogeneous broadening of the transition from ₁ to ⁵ D _2, due to that not to excite all the Eu atoms are excited to the ⁵ D ₁ to ⁵ D _2.

Further, the driving frequency of the PbS _1-x Se _x semiconductor laser L3 is increased to increase the oscillation frequency to 2413.
In place of cm ⁻¹ , ΔI _lu (ω _p ;
FIG. 26 shows the result of obtaining ω _c ).

The region of the (ω _p , ω _c ) plane is shown in FIG.
5, it is clearly seen that a fluorescent hole associated with EIT of a pseudo atom (physical structure) different from that shown in FIG. 25 is observed.

By changing the driving current flowing through the laser L3 to change the oscillation frequency in this manner, ⁵ D ₁ to ⁵ D
_By scanning the entire nonuniform width range of transition to ₂ , it becomes possible to observe (reproduce) EIT signals (information) for all Eu atoms by fluorescence. (Seventh Embodiment) Here, a method of reproducing information recorded on a recording medium and a method of recording new information by using the recording / reproducing apparatus of the present invention will be specifically described.

FIG. 27 is a diagram schematically showing the recording / reproducing apparatus in this embodiment. In reproducing information,
The output light from the two ring dye lasers 11 and 12 is applied to the recording medium 13.

The output light of the laser 11 passes through the recording medium 13 and then is input to the output detecting photomultiplier 14. Output of photomultiplier 14 I ^S _PM1
Since (ω _p ) is an analog signal, it is input to the data control personal computer 16 after being converted into a digital signal by the AD converter 15.

Here, in order to convert the intensity of the incident light on the recording medium 13, a part of the output light from the laser 11 is branched by the beam splitter 17 and then input to the photomultiplier 18, where the branched light The output ^S _PM2 (ω _p ) of the photomultiplier 18, which is the intensity, is obtained. Output I
^S _PM2 (ω _p ) is also converted into a digital signal by the AD converter 19 and then input to the data control personal computer 16.

Further, in order to obtain the data of the absorption spectrum, the outputs I ⁰ _PM1 (ω _p ) and I ^S of the photomultipliers 14 and 18 when the recording medium 13 is not present.
_PM2 (ω _p ) is measured in advance, and these are input to the data control personal computer 16.

[0151] or without irradiation of the output light of the laser 12, absorption I _ab of angular frequency ω _p (ω _p) is defined by the following equation.

I _ab (ω _p ) = (1 / I ⁰ _PM1 (ω _p ))
(I ⁰ _PM1 (ω _p ) −I ^S _PM1 (ω _p ) · I
_PM2 (ω _p ) / I ^S _PM2 (ω _p )) The personal computer 16 for data control calculates the absorption I _ab (ω _p ) by _performing arithmetic processing corresponding to this equation.
The data control personal computer 16 includes a ring dye laser control personal computer 21,
From 28, the values of the angular frequencies ω _p and ω _c are input as signals.

By such a procedure, the absorption spectrum data I _ab (ω _p ; ω _c ) under irradiation of the laser 12 and the absorption spectrum I ⁰ _ab (ω) when the laser 12 is not irradiated are obtained.
_p ) is obtained for each value of the set of (ω _p , ω _c ) and the value of ω _p , and the reproduction data is stored in the hard disk of the personal computer 16 for data control.

When the data amount is large, it is possible to transfer the data from the hard disk of the data control personal computer 16 to the large capacity external storage device 22 such as a magnetic disk and store the data. Further, when the reproduced data is viewed on the screen, the data may be transferred to the display 23.

To newly record information on the recording medium 13, the following procedure is performed.

That is, in addition to the output lights of the lasers 11 and 12, the output lights of the ring dye laser 24 and the excimer laser 25 also enter the dye amplifier 26 for increasing the output. The laser beam output from the dye amplifier 26 was made incident on the BBO crystal 27, which is a nonlinear optical crystal.
The recording medium 13 is irradiated with high waves to record information by the method described in the fourth embodiment.

At this time, the value of the oscillation frequency of the laser 24 is input from the personal computer 28 to the data controlling personal computer 16 as a signal.

As described above, it is important to monitor the light intensities of the lasers 11, 12, and 24 at the time of recording / reproducing information.
A part of the output light of the lasers 12 and 24 is also branched by the beam splitters 29 and 30, respectively, and then the respective branched lights are input to the photomultipliers 31 and 32, and the outputs of these photomultipliers 31 and 32 are respectively added. It is converted into a digital signal by the converters 33 and 34 and input to the data control personal computer 16 to measure the intensity of the output light of the lasers 12 and 24. In the figure, 35 to 40 indicate mirrors.

[0159]

As described above in detail, according to the present invention, E
By adopting a completely new recording / reproducing principle of utilizing the extremely high frequency resolution of the IT phenomenon, it becomes possible to realize the recording / reproducing of information with the state of atoms or molecules as a recording unit.

[Brief description of drawings]

FIG. 1 is a diagram showing a model of a three-level system.

FIG. 2 is a diagram showing an absorption spectrum with respect to an angular frequency ω _p of probe light showing an EIT characteristic of one physical structure.

FIG. 3 is a diagram showing an absorption spectrum with respect to an angular frequency ω _p of probe light showing EIT characteristics of N physical structures.

FIG. 4 is a diagram showing an absorption spectrum with respect to an angular frequency ω _p of probe light for one physical structure

FIG. 5 is a diagram showing the absorption holes observed in the absorption spectrum with respect to the angular frequency ω _p of the probe light on the ω _p −ω _c plane with the sign reversed for the N physical structures.

FIG. 6 is a diagram showing I _ab (Δω) relating to one physical structure for explaining the recording principle of information in the second embodiment.

FIG. 7 shows I _ab (ω _p ; ω _c ), Δ regarding one physical structure for explaining the principle of reproducing information in the second embodiment.
Diagram showing distribution of I _ab (ω _p ; ω _c )

FIG. 8 shows I _ab (ω _p ; ω _c ), Δ relating to the N physical structure for explaining the principle of reproducing information in the second embodiment.
Diagram showing distribution of I _ab (ω _p ; ω _c )

FIG. 9 is a diagram showing an energy distribution of a physical structure populated by irradiation of first and second coherent light.

FIG. 10 is a diagram for explaining a recording method when Ω _p <Ω _c in the third embodiment.

FIG. 11: Physics that cause ionization and structural change by being excited to the fourth level by the irradiation of the third coherent light in the physical structure populated by the irradiation of the first and second coherent lights. Diagram showing energy distribution of structure

FIG. 12 is a diagram for explaining a recording method when Ω _p > Ω _c in the third embodiment.

FIG. 13 is a diagram showing an energy distribution of a physical structure that is not population-trapped by irradiation of first and second coherent light and that is absorbed by the first coherent light and excited to a third level.

FIG. 14 is a diagram for explaining a recording method for a physical structure that does not cause a population trap.

FIG. 15 is an energy level diagram of Eu used in the fourth embodiment.

FIG. 16 shows 1895.20000 with respect to ΔI _ab (ω _p ; ω _c ) measured before recording in the fourth embodiment.
^{_{cm -1 <ω p <18952.0200cm -1}} , 1848
6.0000 cm ^-1 <ω _c <18486.0200 cm
^{-Enlarged view} of area ^-1

17 is a graph showing ΔI _ab (ω) measured before recording in the fourth embodiment, which is 465.9880 cm ⁻¹ <Δ.
The figure which expands and shows the area of ω <466.0020 cm ^-1

FIG. 18 is a diagram showing ΔI _ab (ω _p ; ω _c ) read out after the information recording operation (1) in the fourth embodiment.

FIG. 19 shows ΔI _ab (ω _p ; ω _c ) read after the information recording operations (1) and (2) in the fourth embodiment.
Figure showing

FIG. 20 shows ΔI read out after information recording operations (1), (2), and (3) in the fourth embodiment.
Diagram showing _ab (ω _p ; ω _c ).

FIG. 21 shows ΔI _ab (Δ read out after information recording operations (1), (2), and (3) in the fourth embodiment.
ω)

FIG. 22 is a diagram showing ΔI _ab (Δω) before recording information in the fifth embodiment.

FIG. 23 is a diagram showing ΔI _ab (Δω) after recording information in the fifth embodiment.

FIG. 24 is a diagram showing an energy level of a YAG crystal containing 0.1 mol% of Eu as a recording medium of the sixth embodiment.

FIG. 25 is a (ω _p , ω _c ) plane showing a result of reading information recorded on the recording medium of the sixth embodiment.

FIG. 26 is another (ω _p , ω _c ) plane showing the result of reading the information recorded on the recording medium of the sixth embodiment.

FIG. 27 is a diagram schematically showing the recording / reproducing apparatus of the seventh embodiment.

[Explanation of symbols]

| 1> ... first level | 2> ... second level | 3> ... third level ω _p ... frequency of probe light (first coherent light) ω _c ... coupling light (second) Coherent light) Ωp ... Rabi frequency of probe light Ωc ... Rabi frequency of coupling light 11, 12 ... Ring dye laser 13 ... Recording medium 14 ... Photomultiplier 15 ... AD converter 16 ... Personal computer 17 ... Beam splitter 18 Photomultiplier 19 AD converters 20, 21 Personal computer 22 External storage 23 Display 24 Ring dye laser 25 Excimer laser 26 Dye amplifier 27 BBO crystal 28 Personal computer 29, 30 Beam splitter 31 , 32 ... Photomultiplier 33, 34 ... AD Converter 35 to 40 ... mirror

Claims (9)

[Claims] 1. A solid having a physical structure having an energy level structure composed of three or more energy levels is used as a recording medium, and the number of the physical structures contained in the solid is N, i-th. Let the three predetermined levels of the physical structure of the first level be the first, second, and third levels, and h be Planck's constant, and let the energy of the first level be h
ω _i1 / 2π, the energy of the second level is hω _i2 / 2π,
The third level of energy _{hω i3 / 2π, | ω i3} -ω i1 | the _{ω i31, | ω i3 -ω i2} | the ω _i32, |
When ω _i2 −ω _i1 | is ω _i21 , information is recorded on the recording medium by changing the distribution of (ω _i31 , ω _i32 ) in the N physical structures, and (ω _i31 , ω _The recording / reproducing method, wherein the information is reproduced by detecting the distribution of _i32 ) or the distribution of ω _i21 . _2. The maximum value of ω _i31 among the N physical structures is max (ω _i31 ), the minimum value is min (ω _i31 ), and the maximum value of ω _i32 among the N physical structures is max (ω
_i32 ), the minimum value is min (ω _i32 ), the angular frequency of the first coherent light is ω _p , and the angular frequency of the second coherent light is ω _c , min (ω _i31 ) <ω _p <max (Ω _i31 ), min
Irradiating the recording medium with the first coherent light and the second coherent light satisfying the condition of (ω _i32 ) <ω _c <max (ω _i32 ), and absorbing the first coherent light in the recording medium, and By measuring at least one of the fluorescence of the recording medium generated via the absorption of the first coherent light for a plurality of (ω _p , ω _c ) pairs,
The recording / reproducing method according to claim 1, wherein the information recorded on the recording medium is reproduced. _3. The maximum value of ω _i31 among the N physical structures is max (ω _i31 ), the minimum value is min (ω _i31 ), and the maximum value of ω _i32 is N among the N physical structures. max (ω
_i32 ), the minimum value is min (ω _i32 ), the angular frequency of the first coherent light is ω _p , the angular frequency of the second coherent light is ω _c , ω _p −ω _c is Δω, Δω is constant, and min (Ω _i31 ) <ω _p <max (ω
_i31 ), min (ω _{i3 2} ) <ω _c <max (ω _i32 ), and the first and second coherent light in the recording medium when the recording medium is irradiated with the first and second coherent light. Absorption of coherent light is represented by I _ab (ω _p ; ω _c ),
When the fluorescence of the recording medium generated through the absorption of the first coherent light is I _lu (ω _p ; ω _c ), I _ab (Δω) = ∫I _ab (ω _p ; ω _p −Δω) dω _p and I _lu (Δω) = ∫I _lu (ω _p ; ω _p −Δω) dω _p are obtained for a plurality of different Δω to reproduce the information recorded on the recording medium. The recording / reproducing method according to claim 1. 4. The solid has a fourth level which causes a structural change when an electron is excited in the level, and the energy of the fourth level is hω _i4 / 2π, | ω _i4 −
ω _i1 | is ω _i41 , | ω _i4 − ω _i2 | is ω _i42 , | ω _i4 − ω
_i3 | is ω _i43 , and the maximum value of ω _i41 among the N physical structures is max (ω
_i41 ), the minimum value is min ( _ωi41 ), and the maximum value of _ωi42 among the N physical structures is max ( _ωi41 )
_i42 ), the minimum value is min (ω _i42 ), and the maximum value of ω _{i43 in} the N physical structures is max (ω _i42 ).
_i43 ), the minimum value is min (ω _i43 ), the Rabi frequency of the first coherent light is Ω _p , and the Ravi frequency of the second coherent light is Ω _c, and when Ω _p <Ω _c , On the recording medium, the first and second coherent light beams, and max (ω _{i4 1} ) greater than max.
Angular frequency smaller than (ω _i41 ), or min
(Omega _i43) irradiating the third coherent light having a smaller angular frequency than larger max (ω _i43) than, in the case of Ω _p> Ω _c is the recording medium, wherein the first, second Coherent light of and max (ω _{i4 2} ) greater than min (ω _{i4 2} )
Angular frequency less than _i42 ) or min (ω _{i4 3} )
The information is recorded on the recording medium by irradiating a third coherent light having an angular frequency larger than max (ω _i43 ) and larger than max (ω _i43 ).
The recording / playback method described in. 5. A recording medium comprising a solid having an energy level structure composed of three or more energy levels, and an optical system for irradiating the recording medium with first and second coherent light. In the optical system, the number of the physical structures contained in the solid is N, three predetermined levels of the i-th physical structure are first, second, and third levels, and h is Planck's level. As a constant, the energy of the first level is hω _i1 / 2π, and the energy of the second level is hω _i2 / 2.
π, the energy of the third level is hω _i3 / 2π, | ω _i3 −ω _i1 | is ω _i31 , | ω _i3 −ω _i2 | is ω _i32 , and ω _i31 of the N physical structures is The maximum value is max (ω
_i31 ), the minimum value of ω _{i32 in} the N physical structures is min (ω
_i32 ), where ω _{p is} the angular frequency of the first coherent light and ω _c is the angular frequency of the first coherent light, min (ω _i31 ) <ω _p <max (ω _i31 ), and mi
Recording / characterizing means for changing the angular frequency of the first and second coherent light within a range satisfying a condition of n (ω _i32 ) <ω _c <max (ω _i32 ).
Playback device. 6. When ω _p −ω _c is Δω, the optical system has means for changing the angular frequencies of the first and second coherent light under the condition that Δω is constant. Item 5. The recording / reproducing device according to item 5. 7. The solid has a fourth level that causes a structure change when an electron is excited in the level, and the optical system sets the energy of the fourth level to hω _i4 / 2π, | ω _i4 −
ω _i1 | is ω _i41 , | ω _i4 − ω _i2 | is ω _i42 , | ω _i4 − ω
_i3 | is ω _i43 , and the maximum value of ω _i41 among the N physical structures is max (ω
_i41 ), the minimum value is min ( _ωi41 ), and the maximum value of _ωi42 among the N physical structures is max ( _ωi41 )
_i42 ), the minimum value is min (ω _i42 ), and the maximum value of ω _{i43 in} the N physical structures is max (ω _i42 ).
_i43 ), the minimum value is min (ω _i43 ), the Rabi frequency of the first coherent light is Ω _p , and the Ravi frequency of the second coherent light is Ω _c, and when Ω _p <Ω _c , On the recording medium, the first and second coherent light beams, and max (ω _{i4 1} ) greater than max.
Angular frequency smaller than (ω _i41 ), or min
(Omega _i43) irradiating the third coherent light having a smaller angular frequency than larger max (ω _i43) than, in the case of Ω _p> Ω _c is the recording medium, wherein the first, second Coherent light of and max (ω _{i4 2} ) greater than min (ω _{i4 2} )
Angular frequency less than _i42 ) or min (ω _{i4 3} )
_6. The recording / reproducing method according to claim 5, further comprising means for irradiating the third coherent light having an angular frequency larger than max (ω _i43 ) and smaller than max (ω _i43 ). 8. The means for measuring at least one of the absorption of the first coherent light in the recording medium and the fluorescence of the recording medium generated through the absorption of the first coherent light in the recording medium. The recording / reproducing apparatus for recording according to any one of claims 5, 6, and 7, characterized in that it has. 9. | ω _i2 -ω _i1 | the when the omega _i21, N pieces of physical structure in (ω _i31, ω _i32) and distributed by changing the recording information on the recording medium, the ( ω _i31 ,
8. The recording / reproducing apparatus for recording according to claim 5, wherein the information is reproduced by detecting a distribution of ω _i32 ) or a distribution of ω _i21. .