JPH10197909A - Optical switching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical switching device by a heterodyne detection system of simple constitution. SOLUTION: The light pulses generated by a titanium sapphire laser 2 are divided by a beam splitter 4 to pumping light 14 and probe light 15 and are made incident at the same point of a nonlinear optical element 18 by a lens 16. Glan-tailer polarization prism pairs 17, 21 of which the planes of polarization of transmitted light intersect orthogonally with each other are arranged on a probe optical path. The Kerr signal obtd. by simultaneously making the pumping light 14 and the probe light 15 incident and the probe transmitted light of the Glan-tailer polarization prism 21 generated by impressing a stress on the nonlinear optical element 18 by using a material holder 19 are made output. As this time, the external force shown by an arrow 27 is impressed on the nonlinear optical element 18 by the sample holder 19 so that heterodyne amplification is obtd. by the stress generated in the nonlinear optical element 18 in such a manner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-high-speed optical switch device required for next-generation optical communication technology and optical information processing technology.

[0002]

2. Description of the Related Art With the advent of an advanced information society, optical communications,
In the field of optical information processing technology, the need for ultra-high-speed optical switching devices has been increasing. For example, taking a large-capacity trunk communication network using an optical fiber communication system as an example, at present, in this system, a transmitter or a receiver performs conversion from an electric signal to an optical signal or vice versa. Here, the speed of the optical switch needs to be increased.

However, it has been pointed out that if the data transfer rate further increases, it will be impossible to follow the current electronic circuit, and various basic researches are being advanced to overcome this. A detailed description on this point is described in, for example, the following document. “I Triple E Circuit and Device Magazine” (PWSmith, IE
EE Circuits and devices magazine, May, 9 (1987)).

As one of the candidates for the ultrahigh-speed optical switch element, there is an optical control optical switch using a third-order nonlinear optical effect. Therefore, the concept of the light control optical switch will be described using a car shutter arrangement degenerate four-wave mixing method shown in FIG.

In FIGS. 2 (a) and 2 (b), light generated from a light source (not shown) is used as a probe light 32.
Polarizers 33 and 36 whose polarization planes to the transmitted light are orthogonal to each other are installed in pairs, and a non-linear optical medium 35 such as carbon disulfide is installed between them. Here, as shown in the figure, the polarization plane of the polarizer 33 is parallel to the paper plane, and the polarization plane of the polarizer 36 is perpendicular to the paper plane. Therefore, the polarization plane of the probe light 32 transmitted through the polarizer 33 is in the vertical direction. Becomes a linearly polarized probe light 38 parallel to.

Therefore, in this state, as shown in FIG. 2A, the vertical linearly polarized probe light 38 passing through the first polarizer 33 passes through the nonlinear optical medium 35 as it is, Since the light reaches the polarizer 36, it is blocked here. That is, as shown in FIG. 2A, when only the probe light 32 is incident on the nonlinear optical medium 35, the light transmitted through the polarizer 36 is not detected, and this state corresponds to the switch OFF state.

Next, as shown in FIG. 2B, light from the same light source as the probe light 32 is branched from the probe light 32 to form a pump light 34, which is linearly polarized at an angle of 45 ° from the vertical direction. After the pump light 39, the nonlinear optical medium 3
It is assumed that the light is incident on the same point as the incident point of the linearly polarized probe light 38 of No. 5.

Then, the incidence of the pump light 39 causes anisotropy of the refractive index in the nonlinear optical medium 35 in a direction perpendicular to the direction parallel to the plane of polarization of the pump light 39. As a result, the plane of polarization of the probe light is changed. The linearly polarized light 38 is converted into the elliptically polarized light 40, and light that passes through the polarizer 36 appears. This corresponds to the switch ON state.

Here, as the performance index of such an optical switch, the following three types are tentatively selected. Third-order nonlinear optical susceptibility corresponding to signal strength χ ⁽³⁾ Response time τ corresponding to switching time Absorption coefficient α indicating transparency

[0010] The target values are listed below. χ ⁽³⁾ > 10 ^-7 [esu] τ <1 [ps] α <10 ² [cm ^-1 ]

However, at present, no material satisfying the above target value has been found. For a detailed description of this optical switch, please refer to the “Next-Generation Project Around the World”
It is described in Chapter 5 “Optoelectronic Materials” of Kabun Publishing (1992).

On the other hand, along with the development of the above-mentioned materials, researches for increasing the detection sensitivity of such optical switches have been advanced. Among them, an optical heterodyne detection method is one of the detection methods expected to have high sensitivity. . Therefore, this heterodyne detection method will be described with reference to FIG. 3 by taking as an example a case where the heterodyne detection method is applied to the optical switch having the car shutter arrangement shown in FIG. In FIG. 3, the overall arrangement is the same as in FIG. 2, except that the polarization axis 51 of the polarizer 36 is
Is rotated by a small angle (<1 °) from the orthogonal state with the polarization axis 47 so that a part of the probe light 32 is transmitted from the polarizer 36 (38 → 40 → 46).

In this state, the pump light 39 is made incident on the nonlinear optical medium 35 simultaneously with the probe light 32,
At this time, the light intensity of the transmitted light 46 from the polarizer 36 is represented by I _T
Then, this satisfies the following equation (1). _{I T = I LO + n 2} c / (8π) (E * R E LO + E * LO E R) + I R ............ (1) where, n _2: Linear refractive index c: light velocity I _LO: Pump light intensity of the signal light by the optical 39 and the probe light 32 E _LO: the optical field of the signal light by pumping light 39 and the probe light 32, I _R: light intensity of the probe light transmitted by the misalignment of the polarizer 33, 36 E _R: Optical field of probe transmitted light due to misalignment of polarizers 33 and 36 Note that the probe transmitted light may be hereinafter referred to as reference light.

In the right side of the above equation (1), the first term is a normal signal light, the second term is a hetero-amplified light obtained by interference, and the third term is a reference light. When the reference light I _R is larger than the signal light I _LO , the hetero-amplified light is larger than the normal signal light I _LO by 2Ｅ | E _R | / | E _LO |. Therefore, in the heterodyne detection method, high sensitivity is obtained by detecting the hetero-amplified light obtained by the interference.

This heterodyne detection method is described in McM
Orrow et al. performed heterodyne Kerr measurement of a carbon disulfide solution and observed a signal having an intensity 30 to 50 times that of a normal Kerr signal.

Note that this car shutter arrangement heterodyne detection is described in the literature, iTripleE Journal Quantum Electronics (D. McMorrow, WTLots
haw, and GA Kenney-Wallace, IEEE J. Quantum Electro
n. 24, p. 443 (1988)).

[0017]

The prior art described above does not take into account the fact that the arrangement of the optical elements requires high precision, and has a problem that the configuration is complicated. That is, in the apparatus of the night car shutter arrangement optical heterodyne detection system according to the above-described conventional technology, it is necessary to shift the polarizer pair on the optical path of the probe light from the orthogonal state by a small angle. The structure becomes complicated. An object of the present invention is to provide an optical switch device using a heterodyne detection system having a simple configuration.

[0018]

SUMMARY OF THE INVENTION An object of the present invention is to use a nonlinear optical medium exhibiting a third-order nonlinear optical effect, and to refer to signal light generated in a third-order nonlinear optical process of pump light and probe light in the nonlinear optical medium. In the optical switch device of the type that performs heterodyne amplification of the signal light by light, it is achieved by configuring the nonlinear optical medium with a medium having a refractive index anisotropy given by stress.

In other words, the optical switch device according to the present invention uses a nonlinear optical medium exhibiting a third-order nonlinear optical effect,
Heterodyne amplification of the signal light is performed by signal light generated in a third-order nonlinear optical process by one or more pump lights and one probe light, and reference light generated by applying an external force to the nonlinear optical medium. .

Further, the present invention provides a means for injecting the pump light and the probe light into the nonlinear optical medium, a means for controlling a polarization state of the pump light and the probe light, and a means for applying an external force to the nonlinear optical medium. And means for making the signal light incident on a detector, and a photodetector for detecting the signal light.

Next, the present invention is characterized in that the external force applied to the nonlinear optical medium is synchronized with a signal superimposed on the pump light or the probe light, or with the number of repetitions of the pump light or the probe light.

Next, the present invention relates to the use of two pump light beams whose polarization planes are orthogonal to each other, the use of one pump light polarization state as circular polarization, or the use of one pump light probe. It is characterized by using linearly polarized light having an angle other than 0 degrees with respect to the polarization plane of light.

Next, the present invention provides a time division multiplexer.
(MUX) or time-division demultiplexer (DMLPX)
The feature is that it can be used as.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical switch device according to the present invention will be described in detail with reference to the illustrated embodiments.

First Embodiment First, in order to explain the operation principle of the present invention, quartz is used as a nonlinear optical medium, an external force is applied thereto, and a stress is generated. An example in which a car signal is obtained by performing degenerate four-wave mixing in the car shutter arrangement will be described with reference to the embodiment of FIG.

FIG. 1A shows a titanium sapphire laser 2 excited by an argon laser 1 as shown in FIG.
The optical pulse train having a center wavelength of 800 nm, a repetition frequency of 76 MHz, a pulse width of 80 fs, and a pulse energy of 10 nJ is split into two beams by the beam splitter 4 to obtain pump light and probe light. . One of the beams split by the beam splitter 4 is guided to an optical variable delay path 5, a Glan-Taylor polarizing prism 6, and a mirror 7, passes through an optical chopper 8, becomes pump light 14 and is incident on a lens 16, and the other is , Mirrors 9, 10, 11, 1/2 wavelength plate 1
2. Guided by the mirror 13, the optical chopper 8
, And becomes the probe light 15 and enters the lens 16.

The pump light 14 is guided to an optical variable delay path 5 controlled by a computer 26. The optical variable delay path 5 has a configuration in which two mirrors are placed on a rectilinear stage driven by a stepping motor. The incident light parallel to the rectilinear direction is returned as parallel light having the opposite direction and the same height. When the stepping motor is rotated by one step, the optical path changes by 0.002 mm.

Thus, the pump light 14 and the probe light 1
The optical path length of the sample No. 5 is made equal, and then parallel light is made incident on the lens 16 to be condensed on the same point of the sample 18 as a nonlinear optical medium. At this time, the pump light 14
The angle formed by the incident direction of the probe light 15 was 12 degrees. The sample 18 has a thickness of 1 mm and a surface accuracy of 1/1.
A zero-wavelength quartz substrate is used.

The light transmitted through the probe, ie, the reference light, transmitted through the sample 18 is passed through the lens 22 to remove the other wavelength scattered light.
3, and the signal is detected by the photomultiplier tube 24. The light transmitted through the pump is spatially removed by using the pinhole 20.

At this time, as described above, the Glan-Taylor polarizing prism 6 is installed on the pump light path, and as a result, the pump light 14 is turned into a linearly polarized light 29 parallel to the horizontal direction as shown in FIG. Has been.

Further, on the optical path of the probe light 15, 1 /
The two-wavelength plate 12 is provided, and a Glan-Taylor polarizing prism 17 is provided between the lens 16 and the sample 18 to convert transmitted light into linearly polarized light inclined at 45 ° from the horizontal direction. As shown in FIG. 1C, the light 15 is converted into linearly polarized light having a polarization plane inclined at 45 ° from the horizontal direction.

Further, a Glan-Taylor polarizing prism 21 for passing linearly polarized light perpendicular to the transmission polarization plane of the polarizing prism 17 is provided between the sample 18 and the lens 22.

A dual chopper 8 is provided on the optical path of the pump light 14 and the probe light 15.
As a result, the pump light 14 and the probe light 15 are subjected to intensity modulation at frequencies f ₁ and f ₂ , respectively, so that the photomultiplier tube 2
4 is input to the lock-in amplifier 25 and lock-in is detected at the reference frequency “f ₁ + f ₂ ”, thereby removing the influence of scattered light such as the pump light 14 and the probe light 15. .

As shown in FIG. 1 (b), the sample 18 has a disk-shaped planar shape and is held by a sample holder 19. The holder 19 is provided with a pressing means such as a screw. With this pressurizing means, as shown by arrow 27,
A vertical stress is applied to the sample 18.

As described above, the pump light 14 incident on the sample 18 is linearly polarized light 29 having a horizontal plane of polarization.
The probe light 15 is linearly polarized light 28 having a polarization plane inclined by 45 ° from the horizontal direction.
When a stress of about 0 N was applied, the probe light that passed through the polarizing prism 21 was about 13 times larger than when no stress was applied.

FIG. 1D shows a transmitted light characteristic 30 detected when stress is applied to the sample 18 and a transmitted light characteristic 31 obtained when no stress is applied. Pump light 14 and probe light 1
5 is obtained with the arrival time difference as the horizontal axis. The delay time difference can be changed at a minimum of 6.7 fs by using the optical variable delay path 5.

As is well known, the quartz constituting the sample 18 has no absorption at the excitation wavelength of 800 nm, and the optical signal is relaxed below the pulse width. Therefore, the waveforms of the characteristics 30 and 31 are both similar to the optical pulse waveform and are symmetric with respect to the time origin.

Here, the characteristic 31 when no stress is applied
Then, the signal strength becomes only the value I _LO shown in the first term on the right side of the equation (1). On the other hand, in the characteristic 30 when the stress is applied, the probe light passing through the polarizing prism 21 is generated, and the heterodyne amplified light having the value represented by the second term on the right side of the equation (1) becomes a signal and has a large intensity.

Specifically, the time t = 0 [fs = 10 ^-15]
[Sec], the signal strength when stress is applied is 86.5 times the signal strength when no stress is applied, and a signal strength that is nearly two orders of magnitude higher can be obtained. According to the present invention, it can be seen that a high-sensitivity optical switch device in which pump light is used as a control input and transmitted probe light is used as a switch output is obtained.

Second Embodiment Next, an embodiment in which the optical switch device according to the present invention is embodied as an optical heterodyne amplification modulator will be described with reference to FIG. In the embodiment of FIG. 4, the output light of the titanium sapphire laser is amplified by a regenerative amplifier to obtain an optical pulse train serving as excitation light. In this case, the optical pulse train has a center wavelength of 800 nm and a repetition frequency of 1 kHz
z, the output is 1 W, and the pulse width is 90 fs.

This optical pulse train is divided into two systems, and is separated into a pulse train as the pump light 53 and a pulse train as the probe light 54 as shown in the figure. Of these, first, the light intensity modulator 5 is placed on the optical path of the pump light 53.
2 is provided, where the light is modulated by a predetermined signal before being incident on the nonlinear optical medium 58.

The light intensity modulator 52 has a pair of polarizers whose polarization planes of transmitted light are orthogonal to each other at both ends of a Pockels cell. When a voltage of 8.5 kV is applied to this Pockels cell, It has the ability to rotate the plane of polarization of transmitted light by 90 degrees. Therefore, the pump light 53 transmits 100% when a voltage is applied, and 0% when no voltage is applied.
It is transmitted (blocked).

At this time, whether or not a voltage is applied to the Pockels cell is controlled by an electric clock signal. This clock signal is generated from the excitation light as follows.

First, a part of the excitation light pulse train (light intensity is 4
mW), the light is then incident on an RN Mach-Zehnder modulator (Mach-Zehnder modulator using a lithium niobate crystal (LiNbO ₃ )), and intensity-modulated. The light enters the photodiode and is converted into an electric signal to obtain a clock signal.

As the RNO Mach-Zehnder modulator, one having an extinction ratio of about 20 dB, a half-wave voltage of 2 V, and an insertion loss (including coupling loss) of about 6 dB is used. Using a function generator, the rise / fall time is 5 ns, the amplitude is 2 V, and the amplitude maximum and minimum time regions are each 0.5.
ms square waves arbitrarily superposed were used.

The control of the pump light 53 is performed as follows. First, when superimposing the signal “1” on the pump light 53 (corresponding to switch ON), the above square wave is applied to the LNO Mach-Zehnder modulator, a high voltage is applied to the Pockels cell, and the pump light 53 is applied. Allow 100% transmission.

The signal "0" is superimposed on the pump light 53.
In the case of switching (equivalent to switch OFF), a square wave is not applied to the LNO Mach-Zehnder modulator, and the pump light 53 is made to transmit 0%.

The nonlinear optical medium 58 has a thickness of 1 mm.
Then, a quartz plate having a surface accuracy of 1/10 wavelength is used, and a piezo element 59 is attached to the quartz plate. Due to the deformation generated in the piezo element 59, the stress in the direction perpendicular to the polarization plane of the incident pump light is applied to the nonlinear optical medium 58. It is configured to be hung.

The piezo element 59 is made of a lead zirconate titanate (PZT) polycrystalline ceramic, and is capable of applying a stress of about 10 N to the nonlinear optical medium 59 when a voltage of about 1 mV is applied. As a performance thing.

Next, a beam splitter 55 and a polarizer 57 are provided on the optical path of the probe light 54, and the light enters the nonlinear optical medium 58 via these components. After the nonlinear optical medium 58, a polarizer 60 whose polarization plane is orthogonal to the polarizer 57 is provided.
Stress is not applied to the nonlinear optical medium 58, and
When the pump light is not incident, the light detector 63
It is configured so that light does not reach.

In the beam splitter 55, a part of the probe light 54 is branched, extracted as a reference light train 62 via a mirror 56, and made incident on a photodetector 64.

The light intensity of the reference beam train 62 extracted by the beam splitter 55 is
In a state where a predetermined stress is applied to the signal "0" when entering the nonlinear optical medium 58 simultaneously pump light 53 obtained by superimposing, to be equal to the light intensity of the reference light I _R which passes through the polarizer 60 It is.

The photodetectors 63 and 64 have a spectral sensitivity wavelength range of 400 to 1060 nm and a peak wavelength of 900, respectively.
nm, and a PIN silicon photodiode exhibiting a response of 1 ns or less.
4 is input to the differential amplifier 65 in the 10 MHz band.

Next, the pump light 53 and the probe light 54
The light pulses having the same number ((1), (2),...) In each pulse train are adjusted by adjusting the lengths of the respective optical paths. It is made to be simultaneously incident into the nonlinear optical medium 58.

Then, a predetermined voltage is applied to the piezo element 59 to apply a predetermined stress to the non-linear optical medium 58. First, a signal is applied while the probe light 54 is incident. Pump light 53 with “0” superimposed
To make a state corresponding to switch OFF. Thus, at this time, since the nonlinear optical medium 58 does not appear nonlinear optical effect, being detected by the photodetector 63 becomes only the reference beam, the intensity becomes I _R.

Next, while the probe light 54 is also being incident, the pump light 53 on which the signal "1" is superimposed is incident to make the state corresponding to the switch ON. Then,
This time, a nonlinear optical effect occurs in the nonlinear optical medium 58, and as a result, light transmitted through the polarizer 60 appears, and (1)
So that the transmitted light I _T of the formula is detected.

Then, the normal signal light I in the equation (1)
_LO Since negligibly small compared to other terms, after all, is this time, the reference light I _R heterodyne amplified light is detected. Therefore, the signal light train output from the photodetector 63 and the reference light train output from the photodetector 64 are compared with the differential amplifier 6.
Type 5, by removing the reference beam I _R, so that only the heterodyne amplified light can be detected.

When examining the signal intensity of the heterodyne amplified light at this time, the signal intensity becomes approximately two orders of magnitude higher than that of a normal signal. Therefore, according to this embodiment, a highly sensitive optical heterodyne amplification modulator is used. An operating optical switch device can be obtained.

Embodiment 3 Next, an embodiment in which the optical switch device according to the present invention is embodied as a time division demultiplexer (DEMUX) of an optical heterodyne amplification system will be described with reference to FIG. In the embodiment of FIG. 5, first, the center wavelength is 800 nm, the repetition frequency is 76 MHz, the output is 1 W, and the pulse width is 90 fs.
The optical pulse train from the titanium sapphire laser is divided into two systems, a pump light 68 composed of an optical pulse train and a probe light 70 composed of an optical pulse train.

First, the pump light 68 is supplied to the optical modulator 67 having the same configuration as the optical modulator 52 in the embodiment shown in FIG.
And superimpose the signal. However, as a function generator for superimposing this signal, the rising edge is 1 ns, the amplitude is 2 V, and the amplitude is the maximum and minimum time region 5 n.
One that can generate a square wave of s is used.

On the other hand, the probe light 70 is first made incident on the cavity damper 69 to change the repetition rate from 76 MHz to 1 kHz. A detailed description of this cavity damper is described in J. Herrman
, "Ultra-short light pulse laser", Kyoritsu Publishing (1991)
Chapter 5, “Synchronous Pump Lasers”.

In addition, also in the embodiment of FIG. 5, the components from the beam splitter 55 to the differential amplifier 65 are:
Including the configuration of the probe optical path and the reference optical path by them,
This is the same as the embodiment of FIG. The embodiment shown in FIG. 5 is greatly different from the embodiment shown in FIG. 4 in that the stress applied to the nonlinear optical medium 58 is not constant but is applied in synchronization with the pulse train of the probe light 70. At one point.

For this reason, in the embodiment of FIG. 5, a part of the probe light 70 is branched and made incident on the PIN photodiode, and the probe light 70 is synchronized with the pulse train (repetition rate: 1 kHz) of the probe light 70 generated thereby. Changing amplitude 1
The pulse signal of mV is configured to be applied to the piezo element 59.

The pump light 68 and the probe light 70 are adjusted so as to be incident on the same point of the nonlinear optical medium 58, and the respective optical path lengths are adjusted, so that the pulses (1), Each pulse of the pump light 68 in which the signals of “1”, “0”, and “1” are superimposed on (2) and (3), respectively, is made to enter the nonlinear optical medium 58 simultaneously.

Then, the probe light 70 transmitted through the polarizer 60 is incident on the photodetector 63 as probe transmitted light 77, is branched by the beam splitter 55, and a part of the probe light 70 guided by the mirror 56 is referred to. The light is incident on the photodetector 64 as light 78 and is converted into an electric signal.
This will be supplied to the differential amplifier 65.

[0066] Also in the embodiment of FIG. 5, as in the embodiment of FIG. 4, when a signal "1" is superimposed on the pumping light 68, the reference light I _R is generated heterodyne amplified light, the pump light 68 When the signal “0” is superimposed, the reference light I
Only _R is generated, whereby only the signal based on the heterodyne amplified light is detected from the differential amplifier 65, and a signal having an intensity approximately two orders of magnitude higher than that of a normal signal can be obtained.

Therefore, according to this embodiment, from the pump light 68 composed of an optical pulse train having a repetition rate of 76 MHz,
Probe light 6 consisting of an optical pulse train with a repetition rate of 1 kHz
9 to obtain a time-division demultiplexer that extracts a signal 82 composed of an optical pulse train having a repetition rate of 1 kHz.

When no pulse light of the probe light 69 consisting of an optical pulse train with a repetition rate of 1 kHz appears at this time, no stress is applied to the nonlinear optical medium 58. Due to the fact that the pulse light of the pump light 68 composed of the optical pulse train is incident on the nonlinear optical medium 58, the possibility of the occurrence of the nonlinear optical effect in the nonlinear optical medium 58 is surely suppressed, and the signal-to-noise ratio is reduced. Can be greatly improved.

Further, embodiments of the present invention include the following. First, the third-order nonlinear optical process in the present invention refers to a phenomenon in which light is generated by electric polarization proportional to the cube of an electric field. Accordingly, specific examples of the embodiment of the present invention include a four-wave mixing process, a light-induced birefringence process, a stimulated Raman process, a Brillouin process, an electron Raman scattering process, a two-photon absorption process, and the like. It is not limited.

By the way, the car shutter arrangement degenerate four-wave mixing process described in the prior art is one form of the four-wave mixing process. The third-order nonlinear optical medium referred to here is a material that exhibits the above-described third-order nonlinear optical effect. Thus, since substances all exhibit a third-order nonlinear optical effect, they can be a target medium in the embodiments of the present invention.

Specific examples include polydiacetylene,
Polyacetylene, poly-para-phenylene benzobisthiazole, poly-para-phenylene benzobisthiazole, poly-para-phenylene benzobisoxazole,
Poly-meta-phenylene 5,5'-bibenzimidazole, polyacene ladder polymer, polymethylphenylsilane, polydi-n-hexylsilane, polydi-n-hexylgermane, polythiophene, polyphenylenevinylene, polythienylenevinylene, polynaphthy Lenvinylene, poly-ortho-substituted phenylacetylene, beta-
Carotene, aromatic compound, cyanine dye, phthalocyanine compound, naphthalocyanine compound, nickel dithionate complex, pseudo isocyanine bromide J aggregate, anthracene, GaAs, ZnSe, CuCl, CuBr,
Examples include CbSe, CdTe, CdSSe, CdS, fine metal particles, GaAs superlattice, barium titanate, and the like, but are not particularly limited thereto.

As a method for producing the above-mentioned nonlinear optical medium in the present invention, various single crystal growing techniques, thin film forming techniques, mixed dispersion techniques and the like can be used. First,
Examples of the single crystal growing technique include a sublimation method, a concentration gradient solution method, a temperature gradient solution method, a Bridgeman method, a Czochralski method, and a zone melt method.

Next, as a thin film forming technique, a thin film forming technique by various dry processes, for example, a vacuum deposition method,
Sputtering method, ICB (Ion Cluster Beam) method, M
BE (Molecular Beam Epitaxy) method, ALE (Atomic
Layer Epitaxy method, MLE (Molecular Layer Epit
axy) method, MO-ALE (Metal Organic Atomic Layer)
Epitaxy) method, MOCVD (Metal Organic Chemical)
A Vapor Depo-sition method or a thin film forming method by various wet processes, for example, a spin coating method, a water surface spreading method, an LB (Langmuir-Blodgett) method, an electrolytic polymerization method, or the like can be used.

Examples of the mixing and dispersing technique include a kneading method, a glass precipitation method, and a polymer precipitation method. Various compounds coexist in the process of these elementization technologies,
They can be mixed by doping or the like. In addition, it is also possible to mix and integrate with various compound devices manufactured by a device forming technology different from these device forming technologies, and the present invention is not limited to those described above.

Next, as materials which can coexist and coexist, inorganic materials include, for example, water, glass, quartz, diamond, silicon dioxide, mica, marble, calcite, single crystal silicon, amorphous silicon, GaAs, CdS, KDP, KT
P (KTiOPO ₄ ), lithium niobate, potassium bromide, Rochelle salt, copper sulfate, calcium fluoride, graphite, tin dioxide, barium titanate, red blood salt, ceramics, ceramics, bentonite, cement, metal or alloy No.

Similarly, organic substances include, for example, ethanol, methanol, acetone, ethyl acetate, polycarbonate, polysulfone, polyarylate, polyester, polyamide, polyimide, polysiloxane, polyethylene terephthalate, polyvinyl acetate, polyethylene,
Polypropylene, acrylic resin, polybutadiene, polyvinyl chloride, polyvinylidene chloride, petroleum resin, melamine resin, epoxy resin, phenol resin, isoprene rubber,
Ethylene propylene rubber, norbonene resin, cyanoacrylate resin, styrene resin, and copolymers of these resins, cellulose, starch, chitin, agar, silk thread, cotton thread,
Nylon, albumin, globulin and other proteins,
Wood, bone meal and the like can be mentioned.

Further, examples of the low molecular organic substance include condensed aromatic compounds such as naphthalene and anthracene, dyes, pigments, urea, tartaric acid, optically active amino acids and the like.

The non-linear optical medium according to the embodiment of the present invention may be subjected to a process for improving the appearance and characteristics, extending the service life, increasing the functionality, etc., before and after the formation. Examples of such processing include, but are not particularly limited to, thermal annealing, radiation irradiation, electron beam irradiation, light irradiation, radio wave irradiation, magnetic field line irradiation, and ultrasonic wave irradiation.

Further, as the nonlinear optical medium used in the present invention, it can be used as it is, or after being formed into a block, plate, fiber, powder or thin film to which an appropriate dopant is added. In this case, in the shape at this time, it can be used together with a different material or another material having a different structure according to the present invention.

Incidentally, a laser is desirable as a light source used in the embodiment of the present invention. Also, a pulsed laser is desirable because the third-order nonlinear optical process depends on the peak power density of light. Specifically, a mode-locked neodymium yag laser, a synchronously-excited dye laser, an incoherent light source using a synchronously-excited dye laser, a Ti: Al ₂ O ₃ laser using a Kerr-lens mode-locking method, a Cr ³ : LiSrAlF ₆ laser, Cr ³ : LiCaAlF ₆ laser, Cr ³ : Li
SrGaF ₆ laser, AlGaAs, GaInAsP, AlGaAsS by current injection method or external modulation method
Examples include a b-based, InAsSbP-based semiconductor laser, a quantum well laser, a bistable semiconductor laser, and a distributed feedback laser, but are not particularly limited thereto.

Next, the pump light in the present invention is light that gives anisotropy to the refractive index of the tertiary nonlinear optical medium, and the probe light is incident on the nonlinear optical medium, This is light for measuring the refractive index anisotropy of the medium from the change in the polarization state after transmission or reflection.

In the present invention, the external force refers to a force that generates a stress in a nonlinear optical medium, thereby changing the refractive index of the medium and causing a refractive index anisotropy in a direction perpendicular to the application direction. Means for applying this external force include those using the Pockels effect, the piezo-electric effect, the Kerr effect, the electrostriction effect, the Faraday effect, the magneto-dielectric effect, or the Cotton-Mouton effect. It is not limited to these.

Next, the heterodyne amplification in the present invention means that the signal light generated in the third-order nonlinear optical process by the pump light and the probe light is a nonlinear light, as shown in the second term on the right side of the above equation (1). This means that the signal is amplified by reference light having a polarization plane perpendicular to the probe polarization plane generated when an external force is applied to the optical medium.

As means used in the present invention, that is, means for inputting pump light and probe light to the nonlinear optical medium and means for inputting signal light to the photodetector, means using mirrors and lenses. Means for direct incidence using a quartz fiber, a plastic fiber, a birefringent optical fiber, and a polarization-maintaining optical fiber, or means using the above-mentioned optical fiber and lens are conceivable, but are not particularly limited thereto.

Next, the polarization control means used in the present invention refers to means for controlling the polarization plane of the pump light and the probe light incident on the nonlinear optical medium. Specific examples include a half-wave plate, a Soleil-Babinet phase plate, and a fiber-type polarization control element, or a combination of a Glan-Thomson polarizing prism, a Glan laser polarizing prism, and a Wollaston prism. However, the present invention is not particularly limited to these.

The signal detecting means used in the present invention refers to a detector for detecting a car signal subjected to heterodyne amplification. In the present invention, since the heterodyne amplification is performed, this detector does not need to be an element having high detection sensitivity. However, since the optical switch is performed at high speed, a detector having a fast response time is desirable.

Specific examples include a PIN photodiode, an avalanche photodiode, a Schottky photodiode, a diffusion photodiode, and a photomultiplier, but are not particularly limited.

Next, the time-division multiplexer (MUX) constituted by the optical switch device according to the present invention is shifted in phase by (2π / n) by the master clock so that the mode-locked pulse train Ii (i) is set so as not to overlap each other. = 1-n)
Are modulated into bit signals by the respective optical modulators, are combined by a multiplexer such as an optical fiber coupler, and perform high bit rate communication. At this time, a non-linear optical medium is provided at the junction, and a pump light train synchronized with each light pulse train is incident to form a waveform.

The time division demultiplexer (DEMUX) constituted by the optical switch device according to the present invention includes a highly repetitive optical pulse train formed by a time division multiplexer (MUX) and the like, and a repetition of an integral number of the repetition number. This means that a number of low repetition rate pulse trains are synchronized, and are incident on the same point of the nonlinear optical medium to detect a signal light train having a repetition number equal to the low repetition rate light pulse train due to the nonlinear optical effect.

[0090]

According to the present invention, it is possible to easily obtain a heterodyne amplification type optical switch device having a simple structure without requiring a high-precision holder or the like, and to perform high-sensitivity optical switching.

[Brief description of the drawings]

FIG. 1 is a configuration diagram and a characteristic diagram for explaining an operation principle of an optical switch device according to the present invention.

FIG. 2 is an explanatory diagram of an optical switching operation by a car shutter arrangement degenerate four-wave mixing method.

FIG. 3 is an explanatory diagram of an optical switching operation by a conventional heterodyne amplification car shutter arrangement degenerate four-wave mixing method.

FIG. 4 is a schematic diagram showing one embodiment of the present invention.

FIG. 5 is a schematic view showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Argon laser 2 Titanium sapphire laser 3, 7, 9-11, 13 Mirror 4 Beam splitter 5 Optical variable delay line 8 Optical chopper 12 1/2 wavelength plate 14 Pump light 15 Probe light 16 Lens 6, 17, 21 Glan-Taylor polarizing prism Reference Signs List 18 quartz plate sample 19 sample holder 20 iris 22 lens 23 spectrometer 24 photomultiplier tube 25 lock-in amplifier 26 personal computer 27 arrow indicating stress direction 28 probe light polarization surface 29 pump light polarization surface 30 Kerr signal at the time of applying stress 31 stress Kerr signal when not applied 32 Probe light 33, 36 Polarizer 34 Pump light 35 Nonlinear optical medium 37 Signal light 38 Probe incident light polarization plane 39 Pump light polarization plane 40 Probe transmitted light polarization plane 46 Signal light 47 Polarizer 42 transmitted light Polarization plane 51 Photon 45 Transmitted light polarization plane 52 Pump light intensity modulator 53 Pump light pulse train 54 with signal superimposed 54 Probe incident light pulse train 55 Beam splitter 56 Mirror 57, 60 Polarizer 58 Nonlinear optical medium 59 Piezo element for applying stress to nonlinear optical medium 61 Probe output light pulse train 62 Reference light pulse train 63, 64 Photodetector 65 Differential amplifier 66 Detection signal train 67 Modulator 68 Pump light pulse train 69 Cavity damper 70 Probe incident light pulse train 77 Signal light pulse train 78 Reference light pulse train

Claims (4)

[Claims] 1. Using a nonlinear optical medium exhibiting a third-order nonlinear optical effect, the signal light and reference light generated in the third-order nonlinear optical process of the pump light and the probe light in the nonlinear optical medium are used to heterodyne the signal light. An optical switch device of an amplification type, wherein the nonlinear optical medium is formed of a medium having a refractive index anisotropy given by stress. 2. The light according to claim 1, wherein the stress is intermittently applied in synchronization with at least one of the intensity changes of the pump light and the probe light. Switch device. 3. The invention according to claim 1, wherein the polarization state of the pump light is circularly polarized light or linearly polarized light having an angle other than 0 degrees with respect to the polarization plane of the probe light. An optical switch device comprising: 4. The method according to claim 1, wherein the stress uses any one of a Pockels effect, a Piezoelectric effect, a Kerr effect, an electrostriction effect, a Faraday effect, a magnetodielectric effect, and a cotton Mouton effect. An optical switch device characterized by being provided by: