JP2000250079A - Nonlinear optical element, method of manufacturing the same and method of using the same - Google Patents

Abstract

(57) [Problem] To provide a nonlinear optical material having both ultra-high speed and a large third-order nonlinear susceptibility. SOLUTION: A II-VI semiconductor superlattice 1 is formed on a substrate 2 by using a molecular beam epitaxy method, and a part of the substrate is removed by etching to expose the semiconductor superlattice 1 to the substrate 2 side. An anti-reflection film 3 was formed on the exposed surface. Further, a transparent substrate 6 on which a light reflecting film 4 was formed was bonded to a surface of the semiconductor superlattice 1 opposite to the exposed surface via an adhesive layer 5. When this device was used in a wavelength region longer than the exciton absorption peak wavelength of the semiconductor superlattice, a high third-order nonlinear optical susceptibility and a fast nonlinear response speed were obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor superlattice.
The present invention relates to a nonlinear optical element utilizing a nonlinear optical effect, a method of manufacturing the same, and a method of using the same.

[0002]

2. Description of the Related Art A third-order nonlinear optical element using a semiconductor superlattice is promising as an optical device such as an ultra-high-speed optical switch or a harmonic generation element. Attention has been paid.

[0003] Research into the development of conventional materials in this field includes Applied Physics Letter Vol.
Page 5 (Appl. Phys. Lett., Vol. 42, p. 925 1983) and Physical Review B Vol. 44, page 5726 (Phys.
ev. B, Vol. 44, 5726 1991), a III-V semiconductor superlattice (G
aAs / AlGaAs superlattice). Further, as a device using a III-V semiconductor superlattice, there is a study in Applied Physics Letter Vol. 45, page 13 (Appl. Phys. Lett., Vol. 45, p13 1984).

[0004]

The semiconductor superlattice of the above method has the following problems. Generally, it is known that there is a trade-off relationship between the third-order nonlinear optical susceptibility, which is an index of nonlinear optical characteristics, and the nonlinear response speed.
For example, a III-V semiconductor superlattice has a very large third-order nonlinear optical susceptibility (（10 ⁻³ esu), but a response speed (the response speed is usually composed of a fast component and a slow component). It is difficult to reduce the response time to several nanoseconds or less, especially a slow response component has a lifetime of several tens of nanoseconds or more, and when such a material is applied to an all-optical switching element, there is a limit to the switching speed.

Further, while the III-V semiconductor superlattices operate efficiently only in the red light wavelength region, the switching surface density per unit area of the device must be increased for red light having a relatively long wavelength. Is difficult.

Accordingly, the present invention provides a non-linear optical element manufactured by microfabrication of a semiconductor superlattice, which has a high response speed (very few slow response components) and a high third-order non-linear optical susceptibility. The purpose is to provide.
It is another object of the present invention to provide a method of manufacturing the element and a method of using the element suitable for the nonlinear optical element.

[0007]

In order to achieve the above object, a non-linear optical element according to the present invention comprises a substrate, a II-VI semiconductor superlattice formed on the substrate, and a part of the substrate. Is removed and a part of the II-VI semiconductor superlattice is exposed on the substrate side.

[0008] In the nonlinear optical element of the present invention, II
A group-VI semiconductor superlattice is formed, a portion of the substrate is removed, and the II-VI semiconductor superlattice is exposed from the portion where the substrate has been removed. As will be described later, this exposed surface is an incident surface for signal light, control light, and the like.

Further, the method for manufacturing a nonlinear optical element according to the present invention includes a step of forming a II-VI group semiconductor superlattice on a substrate;
Removing a part of the substrate to expose a part of the II-VI semiconductor superlattice to the substrate side.

Further, the method of using the nonlinear optical element of the present invention is directed to a method in which light having a wavelength longer than the exciton absorption peak wavelength of the II-VI semiconductor superlattice is applied to the II-VI element of the present invention.
It is characterized by being incident on a surface where the group III semiconductor superlattice is exposed.

Heretofore, in order to obtain a large non-linear optical effect, light having an exciton absorption peak wavelength of a semiconductor superlattice has been used. However, in the method of use of the present invention, by irradiating light having a wavelength longer than the exciton absorption peak wavelength, a slow response component is reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a sectional view of one embodiment of the nonlinear optical element of the present invention. As shown in FIG. 1, in this nonlinear optical element, a II-VI group semiconductor superlattice (hereinafter, simply referred to as “semiconductor superlattice”) 1 is formed on a substrate 2, and a part of the substrate 2 is further formed. After being removed, a part of the semiconductor superlattice 1 is exposed on the substrate side. In the nonlinear optical element thus configured, a third-order nonlinear optical characteristic based on exciton absorption of the semiconductor superlattice is observed.

In order to increase the quantum confinement effect of Exxington, the well layer of the semiconductor superlattice 1 is made of at least one selected from ZnSe and ZnCdSe,
The barrier layer is preferably made of at least one selected from ZnMgSSe and ZnSSe.

A structure in which the semiconductor superlattice 1 includes well layers having different thicknesses from each other is preferable because it can operate at a plurality of wavelengths. In this case, the semiconductor superlattice 1 includes a first layer group including a well layer having the same thickness, and a second layer including a well layer having a thickness different from the thickness of the well layer included in the first layer group. And a layer group of the above.

Further, it is preferable that the thickness of the well layer of the semiconductor superlattice 1 be 100 nm or less, since the quantum confinement effect can be increased. The thickness of the well layer is 3 nm
-50 nm is more preferable. On the other hand, the thickness of the barrier layer is
10 nm to 50 nm is preferred.

The substrate 2 is made of GaAs and ZnSe.
It is preferably at least one selected from This is because a semiconductor superlattice having high crystallinity can be manufactured.

(Embodiment 2) FIG. 2 is a sectional view showing another embodiment of the nonlinear optical element of the present invention. As shown in FIG. 2, in this nonlinear optical element, an anti-reflection film 3 is formed on the exposed surface of the semiconductor superlattice 1 of the element shown in FIG.

The anti-reflection film 3 is at least one selected from a metal oxide film, a metal fluoride film and a dielectric multilayer film.
It is preferably one. Although not particularly limited, silica, alumina, titania, tin oxide, indium oxide, and the like are preferable as the metal oxide, and calcium fluoride, sodium fluoride, lithium fluoride, magnesium fluoride, and the like are preferable as the metal fluoride. Further, as the dielectric multilayer film, a multilayer film in which SiO ₂ and TiO ₂ are alternately laminated, M
A multilayer film in which gF ₂ and SiO are alternately laminated is preferable.

These optical antireflection films exhibit a low reflectance in an optically wide wavelength range, are chemically and physically stable, have a higher speed, and have a higher nonlinear optical characteristic. It is suitable for manufacturing an element.

(Embodiment 3) FIG. 3 is a sectional view showing another embodiment of the nonlinear optical element of the present invention. As shown in FIG. 3, in this non-linear optical element, a light reflecting film 4 is formed on the surface of the element shown in FIG.
Are formed.

The light reflection film 4 is preferably a metal thin film or a dielectric multilayer film. Although not particularly limited, a film of gold, silver, aluminum or the like is preferable as the metal thin film, and a SiO ₂ / TiO ₂ multilayer film is preferable as the dielectric multilayer film. This is because these films have high reflectivity, are chemically and physically stable, and are suitable for producing a nonlinear optical element having higher speed and larger third-order nonlinear optical characteristics.

(Embodiment 4) FIG. 4 is a sectional view showing still another embodiment of the nonlinear optical element of the present invention. As shown in FIG. 4, in this nonlinear optical element, an anti-reflection film 3 is formed on an exposed surface of the semiconductor superlattice 1 of the element shown in FIG. 1, and further, a surface opposite to the exposed surface. Is formed with a light reflection film 4. The light reflection film 4 is formed in a range including a surface facing the exposed surface on which the light reflection prevention film 3 is formed.

The semiconductor superlattice 1, the antireflection film 3 and the light reflection film 4 described in each of the above embodiments can be formed by a molecular beam epitaxy method, a sputtering method, a vapor deposition method, a chemical vapor deposition method and a sol-gel method. It is preferable to form by at least one selected method. In particular, the semiconductor superlattice 1
Is preferably formed by a molecular beam epitaxy method or a chemical vapor deposition method.
Is preferably formed by a sputtering method or a sol-gel method. As described in the following embodiment, the light reflection film 4 may be formed on another medium in advance, and then integrated with the element together with the medium.

(Embodiment 5) FIG. 5 is a sectional view showing another embodiment of the nonlinear optical element of the present invention. As shown in FIG. 5, this nonlinear optical element includes a light reflecting film 4 like the element shown in FIG. 3, but the light reflecting film 4 is formed on a transparent substrate 6 in advance. It is.

The transparent substrate 6 has a surface on which the light reflecting film 4 is formed.
To the semiconductor superlattice 2 by the adhesive layer 5 with the
Are combined. Here, the transparent substrate 6 is made of SiO_Two, TiO_Two,
Al _TwoO_Three, SiN and AlN
Preferably, there is one. These glasses and ceramics
Is optically transparent over a wide wavelength range and chemically
Because it is also physically stable.

The adhesive layer 5 is preferably made of at least one selected from an epoxy resin and a silicon resin. This is because transparent and strong bonding can be performed.

(Embodiment 6) FIG. 6 is a sectional view showing still another embodiment of the nonlinear optical element of the present invention. FIG.
As shown in FIG. 5, in this nonlinear optical element, an anti-reflection film 3 is formed on the substrate-side exposed surface of the semiconductor superlattice of the element shown in FIG.

The operation of the nonlinear optical element of the present invention will now be described with reference to FIGS. 7 and 8 taking the element shown in FIG. 6 as an example.
This will be described below.

As shown in FIG. 7, when there is no control light, the signal light 7 is incident at an angle of preferably 2 to 10 degrees from the normal direction of the device (perpendicular to the exposed surface of the semiconductor superlattice). Then, a part of the signal light 7 is reflected on the element surface (the exposed surface of the semiconductor superlattice on which the antireflection film is formed), and the reflected light 8
Becomes On the other hand, as shown in FIG. 8, when the signal light 7 is controlled by the control light 9 preferably incident from the normal direction, a diffracted light 10 newly appears due to the third-order nonlinear optical effect. By detecting this, a reflection type all-optical switch can be realized.

It is preferable that the nonlinear optical element of the present invention is operated in a wavelength region where a slow response component is small. actually,
Using the device shown in FIG. 1, the operation of the device was confirmed using white light having a wide wavelength range as the signal light 7 and a laser beam having a predetermined wavelength near the Exxington absorption peak wavelength of the semiconductor superlattice as the control light 9. At this time, control of the signal light 7 by the control light 9 causes the diffracted light 1 by the third-order nonlinear optical effect
0 was observed.

In the above device operation, the response speed was confirmed under the following conditions. The signal light was incident from a direction forming an angle of 2 degrees with the normal direction of the element, and the control light was incident from the normal direction. Further, the intensity ratio between the signal light and the control light was set to approximately 1: 1. When light having a wavelength longer than the exciton absorption peak wavelength, that is, a wavelength band on the low energy side of 0.02 to 0.2 eV is used as the control light, a fast response of approximately 1.0 ps or less is obtained, and a slow response is obtained. It was confirmed that the components were extremely small. As described above, when the device of the present invention is operated in a wavelength region longer than the exciton absorption peak wavelength of the semiconductor superlattice, an ultra-high-speed switch can be realized.

[0033]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

Example 1 In this example, a non-linear optical element having the same configuration as the element shown in FIG. 1 was manufactured.
First, GaAs of 2 inches in diameter held in a substrate holder
On a substrate (thickness: 300 μm, purity: 99.99%), an element or compound is deposited from a deposition source (cell) containing the following element or compound using a molecular beam epitaxy apparatus to form a ZnSe / ZnMgSSe semiconductor superlattice. Produced.

Specifically, Zn (purity 99.999)
%), Se (purity 99.999%), ZnS (purity 9
9.9%), Mg (purity 99.99%) is evaporated by heating, and the shutter disposed on the cell is opened and closed by computer control to control the semiconductor composition while controlling the ZnSe well layer (5 nm) and the ZnMgSSe barrier layer. (30 nm) were alternately stacked on each other to produce a semiconductor superlattice. The superlattice GaAs substrate thus produced is
First, a sulfuric acid-based etching solution was used, and thereafter, the film was partially removed by wet etching using an ammonia-based etching solution.

The exciton absorption of the superlattice was observed in the absorption spectrum of the device thus manufactured, and the peak of the absorption was at 456 nm at room temperature. Further, the third-order nonlinear optical susceptibility by the four-wave mixing method was 2 × 10 ⁻³ esu near the exciton absorption peak.

On the exposed surface of the semiconductor superlattice of the device on the substrate side, a signal light (wavelength 475n) was formed at an angle of 2 degrees from the normal direction.
m) was incident, and laser light having a wavelength of 475 nm was incident from the normal direction as control light. Diffracted light was observed due to the third-order nonlinear optical effect. At this time, the nonlinear response speed of the element was as high as 0.98 ps, and a slow response component was hardly observed. The intensity of the diffracted light with respect to the control light was 1.2%. On the other hand, the signal light has a wavelength of 45.
When a 6 nm laser beam was used, a slow response component of 40 ps was observed in addition to a response of 0.98 ps.

It should be noted that, even when a ZnSe substrate was used in place of the GaAs substrate, an element having no slow response component could be manufactured, as in the case of the GaAs substrate.

Example 2 In this example, a non-linear optical element having the same configuration as the element shown in FIG. 1 was manufactured.
First, GaAs of 2 inches in diameter held in a substrate holder
An element or compound was deposited on a substrate (thickness: 300 μm, purity: 99.99%) from a deposition source (cell) containing the following element or compound by using a molecular beam epitaxy apparatus, and the element shown in FIG. ZnCdS having a similar configuration
An e / ZnSSe semiconductor superlattice was fabricated.

Specifically, Zn (purity 99.999)
%), Se (purity 99.999%), ZnS (purity 9
9.99%), Cd (purity: 99.999%) is heated and evaporated, and the shutter disposed on the cell is opened and closed by computer control to control the semiconductor composition.
Se well layer (5 nm) and ZnSSe barrier layer (30 nm)
And a semiconductor superlattice having a configuration in which 30 layers were alternately laminated, respectively. The superlattice GaAs substrate thus manufactured was partially removed by wet etching using a sulfuric acid-based etchant and then using an ammonia-based etchant.

Exciton absorption of the superlattice was observed in the absorption spectrum of the device thus manufactured, and the peak of the absorption was at 470 nm at room temperature. Further, the third-order nonlinear optical susceptibility by the four-wave mixing method was 4 × 10 ⁻³ esu near the exciton absorption peak.

On the exposed surface of the semiconductor superlattice of this device on the substrate side, a signal light (wavelength 490 nm) was formed at an angle of 2 degrees from the normal direction.
m) was incident, and a laser beam having a wavelength of 490 nm was incident from the normal direction as control light. Diffracted light was observed due to the third-order nonlinear optical effect. At this time, the nonlinear response speed of the element was as high as 1.1 ps, and a slow response component was hardly observed. The intensity of the diffracted light with respect to the control light was 1.0%. On the other hand, the signal light has a wavelength of 470.
When a laser beam of nm is used, a response of 1.1 ps and 48
A slow response component of ps was observed.

Also in this case, an element having no slow response component could be manufactured even when a ZnSe substrate was used instead of the GaAs substrate.

Example 3 In this example, a non-linear optical element having the same configuration as the element shown in FIG. 2 was manufactured.
First, GaAs of 2 inches in diameter held in a substrate holder
On a substrate (thickness: 300 μm, purity: 99.99%), an element or compound is deposited from a deposition source (cell) containing the following element or compound using a molecular beam epitaxy apparatus,
A ZnSe / ZnMgSSe semiconductor superlattice was fabricated.

Specifically, Zn (purity 99.999)
%), Se (purity 99.999%), ZnS (purity 9
9.9%), Mg (purity 99.99%) is evaporated by heating, and the shutter disposed on the cell is opened and closed by computer control to control the semiconductor composition while controlling the ZnSe well layer (5 nm) and the ZnMgSSe barrier layer. (30 nm) were alternately stacked on each other to produce a semiconductor superlattice. The superlattice GaAs substrate thus produced is
First, a sulfuric acid-based etching solution was used, and thereafter, the film was partially removed by wet etching using an ammonia-based etching solution.

Next, a silica (SiO ₂ ) target having a purity of 99.99% was used on the exposed surface of the semiconductor superlattice on the substrate side in an argon gas atmosphere (gas pressure: 2 Pa).
In, using a high frequency magnetron sputtering apparatus SiO ₂
A thin film (thickness λ / 4: λ is the wavelength of control light) was formed to form a light reflection preventing film.

Exciton absorption of the superlattice was observed in the absorption spectrum of the device thus fabricated, and the absorption peak was at 456 nm at room temperature. Furthermore, the third-order nonlinear optical susceptibility by the four-wave mixing method was 2.4 × 10 ⁻³ esu near the exciton absorption peak.

On the exposed surface of the semiconductor superlattice of this element on the substrate side, the signal light (wavelength 472n
m) was incident, and laser light having a wavelength of 472 nm was incident as control light from the normal direction. As a result, diffracted light was observed due to the third-order nonlinear optical effect. At this time, the nonlinear response speed of the element was as high as 1.17 ps, and a slow response component was hardly observed. The intensity of the diffracted light with respect to the control light was 2.8%. On the other hand, the signal light has a wavelength of 45.
When a 6-nm laser beam was used, a slow response component of 49 ps was observed in addition to the response of 1.17 ps.

[0049] Incidentally, as the light reflection preventing film, in place of SiO _2, be used CaF 2, MgF _2, or SiO ₂ / TiO ₂ multilayer dielectric film, it was possible to obtain the same effect. Furthermore, even when a ZnSe substrate was used instead of the GaAs substrate, an element having no slow response component could be manufactured.

Example 4 In this example, a non-linear optical element having the same configuration as the element shown in FIG. 3 was manufactured.
First, GaAs of 2 inches in diameter held in a substrate holder
An element or compound is deposited on a substrate (thickness: 300 μm, purity: 99.99%) from a deposition source (cell) containing the following element or compound by using a molecular beam epitaxy apparatus to form a ZnSe / ZnMgSSe semiconductor superlattice. Produced.

Specifically, Zn (purity: 99.999)
%), Se (purity 99.999%), ZnS (purity 9
9.9%), Mg (purity 99.99%) is evaporated by heating, and the shutter disposed on the cell is opened and closed by computer control to control the semiconductor composition while controlling the ZnSe well layer (5 nm) and the ZnMgSSe barrier layer. (30 nm) were alternately stacked on each other to produce a semiconductor superlattice. The superlattice GaAs substrate thus produced is
First, a sulfuric acid-based etching solution was used, and thereafter, the film was partially removed by wet etching using an ammonia-based etching solution.

Next, on the surface of the semiconductor superlattice opposite to the portion from which the substrate was removed, silica (Si
O ₂ ) and a titania (TiO ₂ ) target having a purity of 99.99% in an argon gas atmosphere (gas pressure: 2
Pa), using a high-frequency magnetron sputtering apparatus,
The SiO ₂ thin film satisfies the condition of film thickness λ / 4n (where λ is the wavelength of control light and n is the refractive index of SiO ₂ )
A light reflecting film was formed by forming a SiO ₂ / TiO ₂ dielectric multilayer film.

Exciton absorption of the superlattice was observed in the absorption spectrum of the device thus fabricated, and the absorption peak was at 458 nm at room temperature. Further, the third-order nonlinear optical susceptibility by the four-wave mixing method was 4 × 10 ⁻³ esu near the exciton absorption peak.

On the exposed surface of the semiconductor superlattice of this element on the substrate side, signal light (wavelength 475n
m) was incident, and laser light having a wavelength of 475 nm was incident from the normal direction as control light. Diffracted light was observed due to the third-order nonlinear optical effect. At this time, the nonlinear response speed of the device was as high as 1.0 ps, and a slow response component was hardly observed. The intensity of the diffracted light with respect to the control light was 2.9%. On the other hand, the signal light has a wavelength of 458.
When a laser beam of nm is used, a response of 1.0 ps and 60
A slow response component of ps was observed.

The light reflecting film was made of SiO ₂ / TiO _2.
Similar effects could be obtained by using an aluminum film (thickness: 1 μm) formed by an ion beam evaporation method instead of the dielectric multilayer film. Furthermore, even when a ZnSe substrate was used instead of the GaAs substrate, an element having no slow response component could be manufactured.

Example 5 In this example, a nonlinear optical element having the same configuration as the element shown in FIG. 4 was manufactured.
First, GaAs of 2 inches in diameter held in a substrate holder
An element or compound is deposited on a substrate (thickness: 300 μm, purity: 99.99%) from a deposition source (cell) containing the following element or compound by using a molecular beam epitaxy apparatus to form a ZnSe / ZnMgSSe semiconductor superlattice. Produced.

Specifically, Zn (purity 99.999)
%), Se (purity 99.999%), ZnS (purity 9
9.9%), Mg (purity 99.99%) is evaporated by heating, and the shutter disposed on the cell is opened and closed by computer control to control the semiconductor composition while controlling the ZnSe well layer (5 nm) and the ZnMgSSe barrier layer. (30 nm) were alternately stacked on each other to produce a semiconductor superlattice. The superlattice GaAs substrate thus produced is
First, a sulfuric acid-based etching solution was used, and thereafter, the film was partially removed by wet etching using an ammonia-based etching solution.

Next, a silica (SiO ₂ ) target having a purity of 99.99% was used on the exposed surface of the semiconductor superlattice from which the substrate was removed, in an argon gas atmosphere (gas pressure: 2P).
In a), using a high-frequency magnetron sputtering apparatus,
An O ₂ thin film (thickness λ / 4: where λ is the wavelength of control light) was formed to form an anti-reflection film. Further, the surface of the semiconductor superlattice opposite to the portion from which the substrate was removed was 99.99% pure.
Of silica (SiO ₂ ) and a titania (TiO ₂ ) target having a purity of 99.99% in an argon gas atmosphere (gas pressure: 2 Pa) using a high-frequency magnetron sputtering apparatus to form a SiO ₂ thin film having a thickness of λ / A SiO ₂ / TiO ₂ dielectric multilayer film was formed as a light reflecting film so as to satisfy the conditions of 4n (where λ is the wavelength of the control light and n is the refractive index of SiO ₂ ).

In the absorption spectrum of the device thus manufactured, exciton absorption of the superlattice was observed, and the absorption peak was at 458 nm at room temperature. Further, the third-order nonlinear optical susceptibility by the four-wave mixing method was 8 × 10 ⁻³ esu near the exciton absorption peak.

On the exposed surface of the semiconductor superlattice of this device on the substrate side, a signal light (wavelength 475 nm) was formed at an angle of 2 degrees from the normal direction.
m) was incident, and laser light having a wavelength of 475 nm was incident from the normal direction as control light. Diffracted light was observed due to the third-order nonlinear optical effect. At this time, the nonlinear response speed of the element was as high as 1.3 ps, and a slow response component was hardly observed. The intensity of the diffracted light with respect to the control light was 3.4%. On the other hand, the signal light has a wavelength of 458.
When a laser beam of nm is used, in addition to the response of 1.3 ps, 45
A slow response component of ps was observed.

Similar effects could be obtained by using CaF ₂ , MgF ₂ , or a SiO ₂ / TiO ₂ dielectric instead of SiO ₂ as the antireflection film. Similar effects could be obtained by using an aluminum film (thickness: 1 μm) formed by ion beam evaporation instead of the SiO ₂ / TiO ₂ dielectric multilayer film as the light reflecting film. . Further, ZnSe is used instead of the GaAs substrate.
Even if a substrate was used, an element having no slow response component could be manufactured.

Example 6 In this example, a nonlinear optical element having the same configuration as the element shown in FIG. 5 was manufactured.
First, GaAs of 2 inches in diameter held in a substrate holder
On a substrate (thickness: 300 μm, purity: 99.99%), an element or compound is deposited from a deposition source (cell) containing the following element or compound using a molecular beam epitaxy apparatus to form a ZnSe / ZnMgSSe semiconductor superlattice. Produced.

Specifically, Zn (purity 99.999)
%), Se (purity 99.999%), ZnS (purity 9
9.9%), Mg (purity 99.99%) is evaporated by heating, and the shutter disposed on the cell is opened and closed by computer control to control the semiconductor composition while controlling the ZnSe well layer (5 nm) and the ZnMgSSe barrier layer. (30 nm) were alternately stacked on each other to produce a semiconductor superlattice. The superlattice GaAs substrate thus produced is
First, a sulfuric acid-based etching solution was used, and thereafter, the film was partially removed by wet etching using an ammonia-based etching solution.

On the other hand, a silica (SiO ₂ ) having a purity of 99.99% and a titania (TiO ₂ ) target having a purity of 99.99% were formed on the surface of a quartz substrate (0.5 mm thick) in an argon gas atmosphere (gas At a pressure of 2 Pa), a high-frequency magnetron sputtering apparatus was used to form an SiO ₂ thin film having a thickness of λ / 4n (where λ is the wavelength of control light, and n is Si
SiO ₂ / Ti so as to satisfy the condition of (O ₂ refractive index).
An O ₂ dielectric multilayer film was formed to form a light reflecting film.

Further, the quartz substrate on which the light reflecting film is formed is
The semiconductor superlattice was bonded using an epoxy adhesive so that the light reflecting film was in contact with the surface of the semiconductor superlattice opposite to the portion where the substrate was removed.

In the absorption spectrum of the device thus manufactured, exciton absorption of a superlattice was observed, and the absorption peak was at 459 nm at room temperature. Further, the third-order nonlinear optical susceptibility by the four-wave mixing method was 5 × 10 ⁻³ esu near the exciton absorption peak.

The signal light (wavelength 475 nm) is applied to the exposed surface of the semiconductor
m) was incident, and laser light having a wavelength of 475 nm was incident from the normal direction as control light. Diffracted light was observed due to the third-order nonlinear optical effect. At this time, the nonlinear response speed of the element was as high as 1.4 ps, and a slow response component was hardly observed. The intensity of the diffracted light with respect to the control light was 3.2%. On the other hand, the signal light has a wavelength of 459.
When a laser beam of nm is used, a response of 1.4 ps is added in addition to 49 ps.
A slow response component of ps was observed.

Similar effects could be obtained by using TiO ₂ , Al ₂ O ₃ , SiN or AlN instead of SiO ₂ as the transparent substrate. Further, even when a silicon-based resin was used instead of the epoxy-based resin as an adhesive for bonding the transparent substrate to the semiconductor superlattice, the characteristics of the element were almost the same as described above. Furthermore, a light reflection film,
Even when the substrates forming the semiconductor superlattice were changed in the same manner as described above, the characteristics of the devices were almost the same.

Example 7 In this example, a non-linear optical element having the same configuration as the element shown in FIG. 6 was manufactured.
First, GaAs of 2 inches in diameter held in a substrate holder
An element or compound is deposited on a substrate (thickness: 300 μm, purity: 99.99%) from a deposition source (cell) containing the following element or compound by using a molecular beam epitaxy apparatus to form a ZnSe / ZnMgSSe semiconductor superlattice. Produced.

Specifically, Zn (purity 99.999)
%), Se (purity 99.999%), ZnS (purity 9
9.9%), Mg (purity 99.99%) is evaporated by heating, and the shutter disposed on the cell is opened and closed by computer control to control the semiconductor composition while controlling the ZnSe well layer (5 nm) and the ZnMgSSe barrier layer. (30 nm) were alternately stacked on each other to produce a semiconductor superlattice. The superlattice GaAs substrate thus produced is
First, a sulfuric acid-based etching solution was used, and thereafter, the film was partially removed by wet etching using an ammonia-based etching solution.

Then, a silica (SiO ₂ ) target having a purity of 99.99% was used on the exposed surface of the semiconductor superlattice from which the substrate was removed, in an argon gas atmosphere (gas pressure: 2P).
In a), using a high-frequency magnetron sputtering apparatus,
An O ₂ thin film (thickness λ / 4: where λ is the wavelength of control light) was formed to form an anti-reflection film.

On the other hand, silica (SiO ₂ ) having a purity of 99.99% and a titania (TiO ₂ ) target having a purity of 99.99% were formed on the surface of a quartz substrate (0.5 mm thick) in an argon gas atmosphere (gas atmosphere). At a pressure of 2 Pa), a high-frequency magnetron sputtering apparatus was used to form an SiO ₂ thin film having a thickness of λ / 4n (where λ is the wavelength of control light, and n is Si
SiO ₂ / Ti so as to satisfy the condition of (O ₂ refractive index).
An O ₂ dielectric multilayer film was formed to form a light reflecting film.

Further, the quartz substrate on which the light reflecting film is formed is
The semiconductor superlattice was bonded to the semiconductor superlattice using an epoxy adhesive so that the light reflecting film was in contact with the surface of the semiconductor superlattice on the side opposite to the portion from which the substrate was removed (opposite the surface on which the antireflection film was formed). .

In the absorption spectrum of the device thus manufactured, exciton absorption of the superlattice was observed, and the absorption peak was at 459 nm at room temperature. Further, the third-order nonlinear optical susceptibility by the four-wave mixing method was 8 × 10 ⁻³ esu near the exciton absorption peak.

The signal light (wavelength 475 nm) is applied to the exposed surface of the semiconductor
m) was incident, and when laser light having a wavelength of 475 nm was incident from the normal direction as control light, diffracted light was observed due to the third-order nonlinear optical effect. At this time, the nonlinear response speed of the element was as high as 1.2 ps, and a slow response component was hardly observed. The intensity of the diffracted light with respect to the control light was 3.8%. The signal light has a wavelength of 45.
When a 9 nm laser beam is used, in addition to the response of 1.2 ps, 4
A slow response component of 6 ps was observed.

In this embodiment, as in the above-described embodiment, even if the transparent substrate, the adhesive, the light reflection film, the light reflection prevention film, and the substrate on which the semiconductor super lattice is formed are changed, The effect was able to be obtained.

Example 8 In this example, a nonlinear optical element having the same configuration as the element shown in FIG. 6 was manufactured.
First, GaAs of 2 inches in diameter held in a substrate holder
On a substrate (thickness: 300 μm, purity: 99.99%), an element or compound is deposited from a deposition source (cell) containing the following element or compound by using a molecular beam epitaxy apparatus to form a ZnSe / ZnMgSSe semiconductor superlattice. Produced.

However, in the present embodiment, the thickness of the well layer of the semiconductor superlattice is set to two types.

Specifically, Zn (purity 99.999)
%), Se (purity 99.999%), ZnS (purity 9
9.9%), Mg (purity 99.99%) is evaporated by heating, and the shutter disposed on the cell is opened and closed by computer control to control the semiconductor composition while controlling the ZnSe well layer (5 nm) and the ZnMgSSe barrier layer. (30 nm) are alternately laminated on each of the 15 layers.
The Se well layer (10 nm) and the ZnMgSSe barrier layer (30
nm) were alternately stacked on each other to produce a semiconductor superlattice. Thereafter, a nonlinear optical element was manufactured in the same manner as in Example 7.

In the absorption spectrum of the device thus manufactured, the exciton absorption of the superlattice is observed. The absorption peaks correspond to the two types of well layer thickness at room temperature of 459 nm (well layer: 5 nm) and 468 nm (well layer). Layer: 10 nm). Furthermore, the third-order nonlinear optical susceptibility by the four-wave mixing method is 8 × 10 ⁻³ esu near the exciton absorption peak.
And 5 × 10 ⁻³ esu.

The signal light (wavelength 484 n
m) was incident, and laser light having different wavelengths of 475 nm and 484 nm was incident from the normal direction, and diffracted light was observed due to the third-order nonlinear optical effect. At this time,
The non-linear response speed of each element was as high as 1.2 ps, and a slow response component was hardly observed. Further, the intensity of the diffracted light with respect to the control light is 3.8% and 3.3%.
Met. On the other hand, the signal light has wavelengths of 459 nm and 468 nm.
Laser light of 46 ps in addition to 1.2 ps response
And a slow response component of 60 ps were observed.

In this embodiment, as in the above-described embodiment, even if the transparent substrate, the adhesive, the light reflection film, the light reflection prevention film, and the substrate on which the semiconductor superlattice is formed are changed, The effect was able to be obtained. Further, even if a ZnSe substrate was used instead of the GaAs substrate, it was possible to manufacture an element without a slow response component.

[0083]

As described above, according to the present invention,
It is possible to provide a nonlinear optical element having ultra-high-speed response and a large third-order nonlinear optical susceptibility.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the nonlinear optical element of the present invention.

FIG. 2 is a sectional view showing another embodiment of the nonlinear optical element of the present invention.

FIG. 3 is a cross-sectional view showing another embodiment of the nonlinear optical element of the present invention.

FIG. 4 is a sectional view showing another embodiment of the nonlinear optical element of the present invention.

FIG. 5 is a sectional view showing another embodiment of the nonlinear optical element of the present invention.

FIG. 6 is a cross-sectional view showing another embodiment of the nonlinear optical element of the present invention.

FIG. 7 is a diagram showing an example of a use state of the nonlinear optical element of the present invention.

FIG. 8 is a diagram showing another example of a use state of the nonlinear optical element of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor superlattice 2 Substrate 3 Light reflection prevention film 4 Light reflection film 5 Adhesion layer 6 Transparent substrate 7 Signal light 8 Reflected light 9 Control light 10 Diffracted light

Claims (15)

[Claims] 1. A substrate, and II-VI formed on the substrate.
A non-linear optical element, comprising: a group II semiconductor superlattice, wherein a part of the substrate is removed and a part of the II-VI semiconductor superlattice is exposed on the substrate side. 2. The nonlinear optical element according to claim 1, wherein an anti-reflection film is formed on a surface where the II-VI semiconductor superlattice is exposed on the substrate side. 3. The method according to claim 1, wherein the side opposite to the surface exposed to the substrate side is provided.
3. The nonlinear optical element according to claim 1, wherein a light reflecting film is disposed on a surface of the II-VI semiconductor superlattice. 4. A transparent substrate on which a light reflecting film is formed,
The group II-VI semiconductor superlattice is integrated with the group II-VI semiconductor superlattice such that the light reflecting film is disposed on the surface of the group II-VI semiconductor superlattice opposite to the surface where the group VI semiconductor superlattice is exposed on the substrate side. The nonlinear optical element according to claim 3, wherein 5. The nonlinear structure according to claim 4, wherein the transparent recording plate and the II-VI semiconductor superlattice are integrated by an adhesive layer interposed between the transparent substrate and the II-VI semiconductor superlattice. Optical element. 6. An adhesive layer comprising at least one selected from an epoxy resin and a silicon resin.
3. The method for manufacturing a nonlinear optical element according to item 1. 7. The transparent substrate on which the light reflecting film is formed is made of SiO.
_{2, TiO 2, Al 2 O} 3, a nonlinear optical element according to any one of claims 4-6 consisting of at least one selected from SiN and AlN. 8. The nonlinear optical element according to claim 3, wherein the light reflection film is a metal thin film or a dielectric multilayer film. 9. An anti-reflection film comprising at least one selected from a metal oxide film, a metal fluoride film and a dielectric multilayer film.
The nonlinear optical element according to claim 2, wherein: 10. The nonlinear optical element according to claim 1, wherein the substrate forming the II-VI group semiconductor superlattice is at least one selected from GaAs and ZnSe. 11. The group II-VI semiconductor superlattice, wherein the well layer is made of at least one selected from ZnSe and ZnCdSe, and the barrier layer is made of ZnMgSSe and ZnSd.
2. The method according to claim 1, wherein the material is at least one selected from Se.
0. The non-linear optical element according to any one of 0. 12. The nonlinear optical device according to claim 1, wherein the II-VI semiconductor superlattice includes well layers having different thicknesses. 13. A step of forming a group II-VI semiconductor superlattice on a substrate, and a step of removing a part of the substrate to expose a part of the group II-VI semiconductor superlattice to the substrate side. A method for manufacturing a nonlinear optical element, comprising: 14. The method for manufacturing a nonlinear optical element according to claim 1, wherein the II-VI semiconductor superlattice, the antireflection film and the light reflection film are formed by a molecular beam epitaxy method or a sputtering method. A method for manufacturing a nonlinear optical element, wherein the method is formed by at least one method selected from the group consisting of a method, a vapor deposition method, a chemical vapor deposition method, and a sol-gel method. 15. The method for using a nonlinear optical element according to claim 1, wherein the light having a wavelength longer than the exciton absorption peak wavelength of the II-VI semiconductor superlattice is emitted from the II-VI. A method of using a non-linear optical element, wherein the non-linear optical element is incident on an exposed surface of a group III semiconductor super lattice.