JPH02194331A - Optical spectrum analyzer - Google Patents

Abstract

PURPOSE:To analyze light spectrum with high resolution by converging light to be measured by means of a cylindrical lens so that it may become flat and irradiating the end face of a light guide with the light. CONSTITUTION:A light beam L emitted from a light source 23 is projected as divergent light from the end face of an optical fiber 26 through an optical fiber 24 and a coupler 25. The light beam L is turned into the collimated beam of light by a collimator lens 21, passes the cylindrical lens 22 and is converged to get flat. As to the converged light beam L, nearly all the quantities of the light irradiates the end face 12a of the light guide and is efficiently incorporated in the light guide 12 from the end face 12a, then guided in the light guide 12 in the state of the collimated beam of light. The light beam L4 projected from the light guide 12 passes a focusing lens 27 and a pin hole 30a and is detected by a photodetector 31. By converging the light to be measured by the cylindrical lens so that it may become flat and irradiating the end face of the light guide with the light, the light spectrum is analyzed with high resolution.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an optical spectrum analyzer that performs optical spectrum analysis, and particularly relates to an optical spectrum analyzer that analyzes optical spectrum using the acousto-optic effect. .

(Prior Art) Various types of optical spectrum analyzers are known to analyze a prior spectrum.

As one of the optical spectrum analyzers that have been widely used in practical use, for example, there is known a so-called Zzerny-Turner type optical spectrum analyzer. This optical spectrum analyzer rotates a diffraction grating that diffracts the irradiated light to be measured, thereby moving the diffracted light on a slit, and detecting the diffracted light through the slit based on the rotation angle of the diffraction grating. This method analyzes the optical spectrum.

Such optical spectrum analyzers are capable of analyzing optical spectra with high resolution.

However, such optical spectrum analyzers are large and heavy, making them difficult to handle, making them unsuitable for portable use, for example. Various optical spectrum analyzers that can be made small and lightweight have been considered, but many of these have the problem of low resolution.

Therefore, the present applicant previously proposed an optical spectrum analyzer that can be made small and lightweight and has high resolution (Japanese Patent Application No. 1.80779/1982). This optical spectrum analyzer includes an optical waveguide formed of a material that allows surface acoustic waves to propagate, and a waveguide that is arranged in a direction that intersects the optical path of guided light as measured light that is input into the optical waveguide and travels within the optical waveguide. Proceed,
surface acoustic wave generating means for generating a surface acoustic wave whose frequency changes continuously to diffract and deflect the guided light in the optical waveguide; The present invention is characterized in that it is comprised of a light detection means for detecting the light to be measured, and a frequency detection means for detecting the frequency of the surface acoustic wave when the light detection means detects the light to be measured.

When guided light guided in an optical waveguide intersects with a surface acoustic wave propagated in this optical waveguide, it is diffracted and deflected due to acousto-optic interaction. This deflection angle δ is δ−20, where θ is the incident angle of the guided light with respect to the traveling direction of the surface acoustic wave. The wavelength of the guided light is λ, and the effective refractive index of the optical waveguide is N.
Let e be the wavelength, frequency, and velocity of the surface acoustic wave, respectively.
, f, ■, then λ. Since Ne and V are constant, if the incident angle θ and the surface acoustic wave frequency f at which the guided light is most efficiently diffracted satisfying the Bragg condition expressed by this equation are known, the guided light, that is, the light to be measured, can be determined. The wavelength λ of is known.

Further, when the guided light (light to be measured) includes a plurality of spectral components having very close wavelengths, each spectral component can be separated by the diffraction effect of the surface acoustic wave. Therefore, for example, if a pinhole plate or the like is placed in front of the photodetector so that the light of each spectral component can be detected individually, each spectral component can be detected even if the wavelengths are close to each other as described above. Components can be measured accurately.

(Problems to be Solved by the Invention) Conventionally, in the above-mentioned optical spectrum analyzer, the optical fiber that guides the light to be measured is directly coupled to the end face of the optical waveguide so that the light to be measured is input into the optical waveguide. The problem was that the input efficiency was low. In other words, the core diameter of the above-mentioned optical fiber is usually around 10 μm, while the optical waveguide thickness is optimally about the wavelength of the surface acoustic wave in terms of the diffraction efficiency of the guided light by the surface acoustic wave, and if the surface acoustic wave frequency is IGHz, it is 3 μm. Since there is a large difference between the core diameter of the optical fiber and the thickness of the optical waveguide, coupling loss tends to increase.

If the input efficiency is low, optical spectrum analysis may become impossible for weak measured light.

Therefore, an object of the present invention is to provide an optical waveguide type optical spectrum analyzer that can efficiently input light to be measured into an optical waveguide.

(Means and effects for solving the problems) The first optical spectrum analyzer according to the present invention is composed of the above-mentioned optical waveguide, surface acoustic wave generation means, light detection means, and frequency detection means. In the optical spectrum analyzer, the optical input means for inputting the light to be measured traveling outside the optical waveguide into the optical waveguide focuses the light to be measured flatly and directs the focused light to be measured against the end face of the optical waveguide. ,
This is characterized by the provision of a cylindrical lens that emits light in a state in which the converging direction coincides with the end face thickness direction.

In addition, the second optical spectrum analyzer according to the present invention is formed on the surface of an optical waveguide in place of the above-mentioned cylindrical lens, and receives the irradiation of the measured light traveling outside the optical waveguide and directs the measured light into the optical waveguide. The device is characterized by being provided with a diffraction grating that inputs the information into the image.

(Example) Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

FIG. 1 shows an embodiment of the first optical spectrum analyzer of the present invention. This optical spectrum analyzer IO includes an optical waveguide 12 formed on a substrate 11 and a linear diffraction grating (Linear Grating C) for light beam output formed on the surface of this optical waveguide 2.
(hereinafter referred to as LGC) 14 and a guided light beam traveling through the optical waveguide 12.
l Transducer (hereinafter referred to as chirp IDT) j7, a high frequency amplifier 19 that applies a high frequency alternating voltage to this chirp IDT 17 in order to generate the surface acoustic wave 15, and a high frequency amplifier 19 that continuously changes (sweeps) the frequency of the voltage. It has a sweeper 20 and a collimator lens 21.

Further, at the position where the light beam L4 emitted from the light beam output LGC 14 is irradiated, there is a pinhole plate 30 and a photodetector 31 such as a photodiode for measuring the intensity of the target light beam L4. is located.

A light amount signal S1 outputted from this photodetector 31 is input to an arithmetic processing circuit 33, which will be described later, and a light amount signal S3 outputted from this arithmetic processing circuit 33 is inputted to a display device 34.

In this embodiment, as an example, the substrate 11 has LiNbO
The optical waveguide 12 is formed by using three wafers and providing a Ti diffusion film on the surface of the wafer. Note that substrate 1
1 may also be a crystalline substrate made of sapphire, Si, or the like. Furthermore, the optical waveguide 12 is not limited to the above-mentioned Ti diffusion, but may also be formed by sputtering, vapor depositing, or the like other materials on the substrate 11. However, this optical waveguide 12 must be formed of a material such as the above-mentioned Ti diffusion film that can propagate surface acoustic waves, which will be described later. Further, the optical waveguide may have a laminated structure of two or more layers.

The chirp IDT 1.7 is manufactured by, for example, applying a positive electron beam resist to the surface of the optical waveguide 12, further depositing an Au conductive thin film thereon, and drawing an electrode pattern with an electron beam.
It can be formed by peeling off the thin film, performing visual imaging, then depositing a Cr thin film and an A1 thin film, and then performing lift-off in an organic solvent. In addition, chirp IDT17 is
When the substrate 11 and the optical waveguide 12 are made of a piezoelectric material, the surface acoustic waves 15 can be generated even if they are installed directly inside the optical waveguide 12 or on the substrate 11.
If this is not the case, a piezoelectric thin film made of, for example, ZnO may be formed on a part of the substrate 11 or the optical waveguide 12 by vapor deposition, sputtering, etc., and the IDT 1.7 may be installed there.

For example, a light beam L emitted from a light source 23 such as a semiconductor laser and subjected to spectrum analysis is emitted as diverging light from the end face of an optical fiber 26 via an optical fiber 24 connected to the light source 23 and a coupler 25. This light beam L is made into parallel light by the collimator lens 21,
Next, the light passes through a cylindrical lens 22 and is focused into a flat shape. The cylindrical lens 22 provides a focused light beam L.
is irradiated onto the end surface 1.2a of the optical waveguide 12, and the direction in which the light beam L is focused coincides with the thickness direction of the optical waveguide 12. Therefore, the entire amount of the focused light beam L is irradiated onto the optical waveguide end face 12a, and the optical waveguide 12 is efficiently guided from the end face 12a.
taken within.

This light beam L1 passes through the optical waveguide]2 in a parallel beam state.
waveguide inside. If the Bragg condition shown in (1) above is satisfied, this guided light beam 1 has a chirp rDT of 1.7
Due to the acousto-optic interaction with the surface acoustic wave I5 emitted from the surface, it is diffracted (Bragg diffraction) as shown in the figure. The diffracted waveguide light L2 is diffracted toward the substrate 11 side at the LGC 14, and is emitted to the outside of the optical waveguide element from the obliquely cut substrate end surface 11a. This emitted light beam L4 is
A focusing lens 27 focuses the light into a small spot.

Hereinafter, the diffraction and deflection of the guided light within the optical waveguide 12 will be explained in detail with reference to FIGS. 2 and 3.

FIG. 2 shows a detailed enlarged view of the chirp IDT 17, and FIG. 3 shows the wave number vectors of the guided light L1 and the surface acoustic wave 15. As shown in FIG. 2, the guided light L1 is incident at a constant angle θ with respect to the traveling direction of the surface acoustic wave 15.

In addition, the wave number vectors of the guided light L1 before entering the surface acoustic wave 15 and the guided light L2 after passing through the surface acoustic wave 15 are respectively Ik
l, IkZ, and the wave number vector of surface acoustic wave 15 is IK
□, when the Bragg condition shown in equation (1) above is satisfied, Ikl +1K1-1 as shown in Figure 3.
(2), and the deflection angle of the guided light L2 with respect to the guided light is δ=2θ. If the incident angle θ is constant as in the case of two series, the deflection angle δ when the above equation (2) is satisfied is also constant. Therefore, the light beam L4 that completely satisfies the Bragg condition and is emitted out of the optical waveguide (2) is emitted in a fixed direction. The bin pole plate 30 in front of the photodetector 31 is arranged so that the light beam L4 is emitted in the above-mentioned fixed direction and passes through the pinhole 30a.

If the wavelength of the guided light (light to be measured) is λ and the wavelength of the surface acoustic wave 15 is A, then 11kl+-2π/λ, and the wavelength of the guided light L2 is also λ, so lkx
l −1lkz l −2π/λ. Therefore, since the incident angle θ is fixed, only one value of 1−2π/A that satisfies the above formula (2) exists for each 1 lkxl. Therefore, when this formula (2) holds true (that is, when the light beam L4 passes through the pinhole 30a and is detected by the photodetector 31)! From the value of lK11, that is, from the value of the surface acoustic wave [5], the wavelength λ can be determined.

This wavelength λ can of course be determined from the above equation (1), but it is also possible to determine the wavelength λ using the incident angle θ and the optical waveguide 1 for the guided light L1.
Even if the refractive index Ne of 2 is unknown, it can be determined.

That is, a reference waveguide light having a known frequency (λre(')) is input into the optical waveguide 12, and at that time the wavelength Arel
Suppose that this reference guided light is diffracted by the reference surface acoustic wave of '. In Figure 3, if the wave number vector of the reference guided light is OP1, the wave number vector of the reference surface acoustic wave of wavelength A rer is v3, and the wave number vector of the diffracted reference guided light is OQ, then Δ0PQ(1)ΔSPR, so 0P -2yr/λref', PQ-2π/8re
Since r, λ=λref(Δ/Arer) Here, the velocity and frequency of the surface acoustic wave 15 are respectively Vlf
, the velocity and frequency of the reference surface acoustic wave are respectively Vral'
If Sf ref, v −f ASvref'−fref' ΦA, rc
Since f' 5v=vrer, from the above equation, λ-λrer(f rcf / f ) −・= f3
It becomes 1. In other words, if you check the wavelength λrat of the reference guided light and the frequency f ref' of the reference surface acoustic wave in advance,
The wavelength λ of the light to be measured can be determined from this equation (3).

As mentioned above, the frequency of the high-frequency alternating voltage applied to the chirb IDT 17 when performing optical spectrum analysis is continuously swept from fwin to flllaX by the sweeper 20. When the frequency of the alternating voltage, that is, the frequency of the surface acoustic wave 15 is swept in this way, the above f
l1lin ,, f If the maxO value is appropriately set, a certain surface acoustic wave frequency f that satisfies the above equation (1)
Diffraction of the guided light is performed most efficiently when (fmjn≦f≦fmax). At this time, the light beam L4 emitted from the optical waveguide 12 passes through the pinhole 30a and is detected by the photodetector 31.

A frequency measuring circuit 32 connected to the sweeper 20 receives a high frequency signal Sf that the sweeper 20 sends to the high frequency amplifier 19.
Then, the ever-changing alternating voltage frequency, that is, the surface acoustic wave frequency f, is determined. This continuously changing frequency f
A signal S2 indicating this is input to the arithmetic processing circuit 33. This arithmetic processing circuit 33 has the wavelength λ of the reference waveguide light mentioned above.
ref' and the frequency f ref of the reference surface acoustic wave are stored in advance, and the arithmetic processing circuit 33 calculates the above-mentioned equation (3) from these wavelengths λref % frequency f ref and the surface acoustic wave frequency f indicated by the signal S2. Based on guided light L
In addition to calculating the wavelength λ of 1, the relationship between the detected light amount and the wavelength λ is determined based on the light amount signal S1 synchronized with the signal S2.

A signal S3 indicating the relationship between the guided light L1, that is, the wavelength λ of the light to be measured and the amount of detected light, is sent to the arithmetic processing circuit 3.
3 and is input to a display device 34 such as a liquid crystal display device or a phototube display device, and based on this signal S3, the relationship between the amount of light and the wavelength λ is displayed in a graph as an example. Therefore, if the wavelength λ at the time when the light beam L4 is detected, that is, when the Bragg condition is satisfied, is found from this display, it becomes the wavelength of the light to be measured.

Note that the display device 34 may be replaced with a suitable recording device or the like. Further, in this embodiment, the wavelength λ of the light to be measured corresponding to the surface acoustic wave frequency f is calculated by the arithmetic processing circuit 33.
is calculated and determined, but such calculations may be performed separately manually. That is, if at least the surface acoustic wave frequency f when the photodetector 31 detects the light beam L4 is detected, the wavelength λ of the light to be measured can be determined.

Furthermore, as in the embodiment described above, not only when the photodetector 31 detects the light beam L4, but also when the surface acoustic wave 15
While sweeping the frequency, find the frequency f,
It goes without saying that the light amount signal S1 may be continuously sent to the arithmetic processing circuit 33 regardless of whether or not the open beam L4 is detected. In this way, the display device 34 clearly shows a wavelength range in which the light beam L4 is not detected at all (that is, a range in which no spectral component exists).

In such a case, since noise components are generally included in the light amount signal 81 and the like, the detected light amount display often does not become 0 (zero) even in the wavelength region where the light beam L4 is not detected. Even if this happens, there is no problem as long as it is known in advance that up to a certain level of the light amount display is a noise component.

Further, in order to avoid such a situation, a predetermined level slightly higher than the above noise component may be displayed as the light ff1o (zero) level. Further, by setting this predetermined level higher than the above, it is possible to display only wavelengths near the center wavelength of the spectrum (one or more longitudinal modes may be used).

Furthermore, in the above embodiment, the relationship between the detected light amount of the light to be measured and the wavelength λ is determined by analog processing, but the light amount signal output from the photodetector 31 is digitized, and the above relationship is determined by digital processing. You can also ask for

Here, the optical spectrum analyzer of the present invention
Even when the tFJ constant light consists of a plurality of spectral components whose wavelengths are very close to each other, each spectral component can be measured with high resolution. This point will be explained in detail below. For example, if the light to be measured has wavelengths λ and λ that are close to each other,
2, λ3 (λ1 × λ2 × λ3).

As shown in FIG. 4, it is assumed that the Bragg condition is satisfied between the guided light of intermediate wavelength λ2 and the surface acoustic wave 15, and the diffracted light is emitted in the direction of vector Ik2. At this time, the guided lights of wavelengths λ1 and λ3 also almost, but not completely, satisfy the Bragg condition with respect to the surface acoustic wave 15. Therefore, the guided lights of these wavelengths λl and λ3 are also diffracted by the surface acoustic wave 15 and exit from the optical waveguide 12.

However, the diffraction angles of these lights are different from the diffraction angles of light with wavelength λ2, and as shown in Figure 4, the diffraction angles of these lights are
, in the direction of vector Ik5 (in Fig. 4, 0
1 and G3 are the starting points of the wave number vectors of the guided lights with wavelengths λ1 and λ3, respectively). Therefore, the light beam emitted from the optical waveguide 12 is separated into each spectral component. If each spectral component is completely separated on the pinhole plate 30 in this way, when the frequency of the alternating voltage is swept, three beam spots move on the pinhole plate 30, and light of each wavelength is pass through the pinholes 30a one after another.

Therefore, the relationship between the amount of light detected by the photodetector 31 and the surface acoustic wave frequency of the alternating voltage frequency band is as shown in FIG. In other words, the wavelengths λ1, λ2, λ
The three spectral components are individually detected when the surface acoustic wave frequencies are fl, T2, and T3, respectively. Once these surface acoustic wave frequencies fl%f' and T3 are detected, the wavelengths λ2 and λ3 can be determined in the same manner as described above.

Next, another embodiment of the first optical spectrum analyzer of the present invention will be described with reference to FIGS. 6.7 and 8. In these Figures 6 to 8, the same elements as those already explained are denoted by the same reference numerals, and the explanation thereof will be omitted unless it is particularly necessary (hereinafter,
similar). As shown in FIGS. 6 and 7, in the optical spectrum analyzer 50 of this embodiment, the optical waveguide 12 is provided with a second chirb IDT 1.8 in addition to the chirb IDT 17. This chive IDT
1g generates the second surface acoustic wave 16,
This surface acoustic wave 16 diffracts and deflects the guided light L2 that has been diffracted and deflected by the first surface acoustic wave 15 in a direction that further amplifies the deflection. In this example, sweep alternating voltages having mutually equal frequencies are applied to the first and second chirped IDTs 17 and 18 from the high frequency amplifier 19. Therefore, the frequencies of the first and second surface acoustic waves 15, 16 change continuously while always maintaining the same value.

In this case, the wave number vectors of the guided light L2 after being diffracted by the guided light Li2 and the guided light L3 after being diffracted by the second surface acoustic wave 16 are IJ
% [lc2, IK3, first and second surface acoustic waves 1
If the wave number vector of 5.16 is IK, , IK2, then
When the above two diffraction steps are performed, lkl +lK1
-1 to 2 1 to 2+lK2-uc3. The chirb IDT 1.7.18 is arranged so that the incident angle of the guided light L2 to the first surface acoustic wave 15 and the incident angle of the guided light L2 to the second surface acoustic wave 16 are equal to each other at θ. In this case, too, the wavelength λ of the light to be measured can be determined based on the frequency f of the first and second surface acoustic waves 15.16, that is, the frequency of the alternating voltage applied to the IDT 17.18. can.

In this example, if the reference guided light and the reference surface acoustic wave (in this example, the first and second reference surface acoustic waves having the same frequency are used) as described above, the above equation (3) is used. The wavelength λ of the light to be measured can be determined based on . In other words, in Fig. 8, the wave number vector of the reference waveguide light is OP1, the wave number vector of the quasi-surface acoustic wave is PQ
, this second reference surface acoustic wave, the wave number vector of the reference guided light diffracted by the reference surface acoustic wave is OQ, the wave number vector of the second reference surface acoustic wave is QT, and this second reference surface acoustic wave. Since Δ0PQQOΔSPR, the above equation (3) is finally established.

However, in this example, the deflection angle δ of the guided light L3 after the second diffraction with respect to the guided light beam is the first surface acoustic wave 1 of the guided light L1.
If the angle of incidence on 5 is θ, it is 40. This is twice the deflection angle δ-20 in the previously described embodiment, so that in this embodiment the resolution of the spectral analysis can be higher than in the previous embodiment. This point will be explained in detail below.

For example, in FIG. 4, the angle between vector 11 (2 and vector 1 and 4 or Ik5 is vector Ik1
The larger the angle between the vectors 1 and 2 is, that is, the larger the diffraction angle of the guided light by the surface acoustic wave. That is, the difference in the emission angles of several light beams simultaneously emitted from the optical waveguide 12 increases as the deflection angle δ of the guided light increases, and each light beam is
At the top, they become separated at larger intervals. If this happens, it will be possible to separate spectral components with closer wavelengths, so that the larger the deflection angle δ is, the better the resolution of spectrum analysis will be.

In the embodiments described above, the frequencies of the first and second surface acoustic waves 15 and 16 are always equal;
．． The 16 frequencies may be set to take different values while always maintaining an equal ratio.

Further, the guided light, which is the light to be measured, may be refracted three times by three or more surface acoustic waves. As mentioned earlier, the resolution of spectral analysis improves as the deflection angle δ of the guided light increases, so if diffraction is performed multiple times in this way, the resolution of spectral analysis can be improved without significantly increasing the frequency of the surface acoustic wave. It is preferable because it can be improved.

In the two embodiments described below, the optical waveguide end face 12a is exposed in the air. In this case, in order to improve the light input efficiency, the end surface 12a has a thickness of, for example, 2 to 3 mm.
It is necessary to uniformly polish the micrometer-sized portion along the waveguide direction to prevent the edges from chipping. On the other hand, as shown in FIG.
．． 2a may be covered by the substrate 11 for a certain length. In this case, the part of the substrate end surface 11b on which the light beam L is incident will be polished over a much thicker range (for example, about several hundred μm to 1 mrn) than the above-mentioned 2 to 3 μm. Bottom surface, board end surface 11
This is advantageous because even if the edge of -b is chipped to some extent, the light input efficiency will not be significantly reduced.

Further, as shown in FIG. 9, the guided light L2 is directly emitted from the optical waveguide end face 12b, and the emitted light beam L4 is passed through the cylindrical lens 28 to be parallelized, and then passed through the converging lens 27 to form a small spot. You may narrow it down to .

Further, as the cylindrical lens 22 for inputting the light to be measured into the optical waveguide, a lens that corrects chromatic aberration can also be used. By using such a cylindrical lens 22, it is possible to prevent the focal position of the narrowed light beam L4 from varying depending on its wavelength. For example, when performing spectrum analysis of semiconductor laser light in the visible region or semiconductor laser light in the long wavelength region, 800-900 nm and 1200-18 nm, respectively.
It is sufficient to have a wavelength measurement range of approximately 00 nm, but it is sufficiently possible to prevent chromatic aberration from occurring within this wavelength range.

Next, a second embodiment of the optical spectrum analyzer of the present invention will be described with reference to FIGS. 10 and 11.

In the optical spectrum analyzer 70 of this embodiment, an LGC 71 for inputting the light to be measured is provided on the surface of the optical waveguide 12.
are provided, and the end surface 1.1. of the substrate 11 is provided. b is cut diagonally so that the light beam L as the light to be measured is irradiated onto the LGC 71 through this substrate end surface 11b. The light beam L thus irradiated onto the LGC 71 is diffracted at the LGC 7I and taken into the optical waveguide 12. In this device as well, the mechanism for determining the wavelength λ of the light beam L is similar to that in the device shown in FIG.

In the above embodiment, the LGC 71 is provided on the surface of the optical waveguide 12 on the air side, but this LGC 71 may be provided on the surface of the optical waveguide on the substrate 11 side.

Furthermore, even when the LGC 71 is used to manually introduce the light to be measured into the optical waveguide 12 as described above, the sixth
As in the device shown, it is possible to refract and deflect the guided light by two equal amounts by different surface acoustic waves.

Note that the light input efficiency of the LGC 71 as described above varies depending on the wavelength of the light beam L. Therefore, as shown in FIG. 12, the light beam L before entering the LGC 71 is passed through a transmission type or reflection type wavelength fluctuation correction diffraction grating 72, and the light beam L is changed from the diffraction grating 72 according to the wavelength fluctuation of the light beam L. The light input efficiency in the LGC 71 may be stabilized by changing the output angle (that is, the incident angle to the LGC 71) of the light.

Regarding such a diffraction grating for wavelength fluctuation correction, the present applicant has filed a patent application (2) dated December 16, 1988.
(Agent Masashi Yanagita et al.)'s detailed description.

(Effects of the Invention) As explained in detail above, according to the optical spectrum analyzer of the present invention, it is possible to analyze the previous spectrum with high resolution. Furthermore, the spectrum analyzer of the present invention has a structure in which the light to be measured enters the optical waveguide and the light to be measured is diffracted by surface acoustic waves, so it is small and lightweight, and has no mechanical operating parts. Because I am not prepared,
It also has high durability and reliability.

Furthermore, the optical spectrum analyzer of the present invention is capable of inputting the light to be measured into the optical waveguide by concentrating the measured light into a flat shape using a cylindrical lens and irradiating it onto the end face of the optical waveguide, or by diffracting it at a diffraction grating formed on the surface of the optical waveguide. (7) Therefore, compared to the case where the optical fiber guiding the constant light to be measured 71Pj is directly coupled to the end face of the optical waveguide, the input efficiency of the light to be measured into the optical waveguide is increased. Therefore, according to this device, the weak light to be measured can be spectrum analysis is also possible.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing an embodiment of the first optical spectrum analyzer of the present invention, FIG. 2 is a plan view showing an enlarged part of the device of the above embodiment, and FIG. 3 is a diagram of the device of the embodiment described above. FIG. 4 is an explanatory diagram illustrating the separation of optical spectra in the device of the present invention; FIG. 5 is a graph showing the relationship between the amount of light detected in the device of the present invention and the surface acoustic wave frequency; FIG. 6 is a schematic perspective view showing another embodiment of the first optical spectrum analyzer of the present invention, FIG. 7 is a plan view showing an enlarged part of the device shown in FIG. 6, and FIG. 8 is the above-mentioned device. An explanatory diagram for explaining the optical beam deflection in the device of FIG. 6, FIG. 9 is a side view showing a part of still another embodiment of the first optical spectrum analyzer of the present invention, and FIGS. 10 and 11 are respectively , a plan view and a side view showing one embodiment of the second optical spectrum analyzer of the present invention, and FIG. 12 is a side view showing another embodiment of the second optical spectrum analyzer of the present invention. 10, 50.70... Optical spectrum analyzer I
I...Substrate I2...Optical waveguide 12a
... Optical waveguide end face 14 ... LGC for forward beam output
15... First surface acoustic wave 16... Second surface acoustic wave I7... First chirp IDT 18... Second chirp IDT 19... High frequency amplifier 20... Sweeper 2
1... Collimator lens 22... Cylindrical lens 23... Light
Source 30... Pinhole plate 30a... Pinhole 31... Photodetector 32... Frequency measurement circuit 33... Arithmetic processing circuit 34... Display device 7I... LGC for light input 72 ... Wavelength fluctuation correction diffraction grating Ll ... Guided light L2 before entering the first surface acoustic wave
... Guided light L3 that has passed through the first surface acoustic wave... Guided light Ik1 that has passed through the second surface acoustic wave... Guided light L
1 wave number vector [k2... wave number vector of guided light L2 + 3... wave number vector 1 of guided light L3 1...
Wave number vector of the first surface acoustic wave IK2... Wave number vector of the second surface acoustic wave 〇-

Claims (2)

[Claims] (1) An optical waveguide formed of a material through which surface acoustic waves can propagate; ,
a surface acoustic wave generating means for generating in the optical waveguide a surface acoustic wave whose frequency changes continuously to diffract and deflect the guided light; and the measured light that is deflected by the surface acoustic wave and emitted out of the optical waveguide. a frequency detection means for detecting the frequency of the surface acoustic wave when the light detection means detects the light to be measured; A cylindrical lens that irradiates the focused light to be measured onto the end face of the optical waveguide in a state where the focused direction coincides with the thickness direction of the end face, and inputs the light to be measured into the optical waveguide. An optical spectrum analyzer. (2) An optical waveguide formed of a material through which surface acoustic waves can propagate; ,
a surface acoustic wave generating means for generating in the optical waveguide a surface acoustic wave whose frequency changes continuously to diffract and deflect the guided light; and the measured light that is deflected by the surface acoustic wave and emitted out of the optical waveguide. a frequency detection means for detecting the frequency of the surface acoustic wave when the light detection means detects the light to be measured; An optical spectrum analyzer comprising a diffraction grating that is irradiated with light to be measured and inputs the light to be measured into an optical waveguide.