JPH10288799A - Optical waveguide circuit and nonlinear optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical waveguide circuit into which an optical waveguide is easily written in spite of an intricate shape. SOLUTION: A glass material 20 exhibiting a nonlinear optical effect is formed as a base body or as part of this base body and the part changed in refractive index by irradiation with the condensed beam of a laser beam is formed as the optical waveguide 25 in the base body. Oxide glass, halide glass, sulfide glass, chalocogenide glass, etc., are used as the glass material 20. The optical waveguide 25 is branched to, for example, a two-forked shape and the one branched optical waveguide 25 is formed within the glass material exhibiting the nonlinear optical effect. As a result, the optical switch of high responsiveness built into an optical Kerr shutter type switch, Mach-Zehnder type switch, directional coupler type switch, etc., is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device useful as an optical switch for an optical data processing, information processing, optical communication system, or the like, an optical memory, an optical signal processing unit, or the like.

[0002]

2. Description of the Related Art As optical devices such as optical switches utilizing the nonlinear optical effect, various types of optical Kerr shutter switches, Mach-Cheander type optical switches, directional coupler type optical switches and the like are known. As shown schematically in FIG. 1, an optical Kerr shutter switch 10 has a polarizer 11 and an analyzer 12 arranged in a crossed Nicols arrangement in which polarization axes are orthogonal to each other, and carbon disulfide or the like sealed in a glass cell. The nonlinear refractive index medium (Kerr medium) 13 is interposed between the polarizer 11 and the analyzer 12. Input light (probe light) P _i is gated by the gate pulse light P _g, the output light P _t corresponding to the time waveform of the gate pulse. In this configuration, only while the gate pulse P _g is incident,
The linearly polarized light of the probe light P _i that has passed through the polarizer 11 changes to elliptical polarization due to a change in the refractive index of the Kerr medium 13. Therefore, a portion of the probe light P _i is able to pass through an orthogonal analyzer 12, probe light P _i by a pulse of the gate pulse P _g
Is optically switched.

The probe light P passing through the analyzer 12_i Through
Excess rate is gate light P_g And probe light P_i Of linear polarization
The maximum is obtained when the angle is π / 4. Probe at this time
Light P _i Is T 率 sin^Two(n_2BLI_gGiven by
You. Where n_2BIs the nonlinear refraction called the Kerr constant
Rate, L is the length of the Kerr medium 13, I_g(= 4P_g/ πD^Two) Is
Light P_g Power density, D is beam spot size
It is. In the waveguide medium, D is regarded as the core diameter.
Can be. Optical car shutter switch using carbon disulfide
Has a fast response of about picoseconds.
I have. However, although high speed is excellent, the driving power
Is extremely high, and the advantages of high speed are fully utilized.
Absent. In developing nonlinear optical devices, optical waveguide
The use of a non-linear optical material as a nonlinear medium
Even if shape is low, it can compensate for it
It is considered one of the effective means. But nonlinear light
Conventional method of fabricating optical waveguides using glass materials
In many cases, processes such as ion exchange and flame hydrolysis are used.
It has gone through the process.

In the ion exchange method, for example, a metal film
Ag to the glass substrate surface layer⁺ Thermal ion
Into the glass, Na in the glass⁺ Ion and Ag⁺ Ion
Waveguide nuclei are formed on the surface layer by the first-stage ion exchange.
Then, apply a uniform electric field to the glass
Na⁺ The ions penetrate the glass surface. Na ⁺ 
The ion is Ag⁺ High refraction region on the outermost surface formed by ions
Is moved below the surface. As a result, the waveguide
It is embedded underneath to ensure low propagation loss characteristics. This one
The core of an optical waveguide manufactured by the method usually has a diameter of 10
With a semi-circular or nearly circular cross section of ~ 200 μm, 1%
Many show the relative refractive index difference before and after. By flame hydrolysis
Is the flame addition of silicon tetrachloride and germanium tetrachloride.
For lower cladding and core on silicon substrate surface by decomposition
Two glass fine-particle layers for
To modify the fine particle layer into a transparent glass layer. Then the photo
Circuit pattern by lithography and reactive etching
To form a core portion having Optical waveguide produced by this method
The path has a thickness of several μm.

[0005]

When an optical waveguide used for a conventional nonlinear optical device is manufactured by an ion exchange method, the refractive index distribution is adjusted by ion exchange, so that the formed waveguide structure is formed on a glass surface. Limited to close parts. The glass for which a waveguide can be formed is also limited to a material that can be ion-exchanged. Also, since it takes a long time for ion exchange,
Another disadvantage is the low productivity. Furthermore, even if optical waveguides having various two-dimensional patterns can be manufactured on the same substrate,
It is difficult to form a three-dimensionally combined optical waveguide. Therefore, there is a restriction on the use as an optical waveguide, etc.,
Cannot be used for applications with complex circuit configurations. As described above, at the time of configuring an optical device using a glass material, the high nonlinear optical characteristics inherent to the material cannot be sufficiently exhibited.

[0006] On the other hand, in the case of the flame hydrolysis method, the manufacturing process of the waveguide is complicated, and the usable material is limited to a glass composition containing quartz as a main component. Further, since the fine particles deposited on the substrate surface are modified into a glass layer, it is difficult to produce an optical waveguide having a circular cross section. Furthermore, even in the flame hydrolysis method, it is difficult to form a three-dimensionally combined optical waveguide similarly to the ion exchange method. The present invention has been devised to solve such a problem, and has a structure in which a focal point of a laser beam is relatively moved inside a glass material having a large nonlinearity, thereby causing a change in a refractive index. An object of the present invention is to provide an optical waveguide circuit in which a change is caused inside a glass material and an optical waveguide of a required shape is easily formed without being substantially restricted by the types of usable glass materials.

[0007]

An optical waveguide circuit according to the present invention comprises:
In order to achieve the object, a glass material exhibiting a non-linear optical effect is used as a base or a part of the base, and a part whose refractive index is changed by condensing irradiation of laser light is formed inside the base as an optical waveguide. Features. As the glass material, oxide glass, halide glass, sulfide glass, chalcogenide glass, or the like is used. The optical waveguide is bifurcated, for example, and one of the branched optical waveguides is formed inside a glass material exhibiting a nonlinear optical effect. This optical waveguide circuit is incorporated in an optical Kerr shutter type switch, a Mach-Cheander type switch, a directional coupler type switch, and the like, and forms an optical switch with high response.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have studied and studied the optical switching characteristics of an optical waveguide produced by converging and irradiating a laser beam, and have reached the present invention. In the optical waveguide according to the present invention, the change in the refractive index is continuously formed inside the glass material due to the irradiation of the laser beam. When forming an optical waveguide in this manner, a non-linear optical device such as an optical switch can be easily manufactured without having to go through a conventional complicated process. The fabricated nonlinear optical device can be used as an optical Kerr shutter switch, a Mach-Cheander type optical switch, a directional coupler type optical switch, etc. All of them can be used for high-speed optical switching by utilizing the third-order nonlinear optical effect. Operation is possible.

The glass material for producing the optical waveguide for the non-linear optical device is not limited as long as it is various non-linear optical glasses having high transparency.
For example, various material systems such as oxide glass, halide glass, sulfide glass, and chalcogenide glass can be used. Examples of oxide glasses having a large third-order nonlinearity include silicate-based, borate-based, phosphate-based, fluorinate-based, germanate-based, and tellurite-based glasses, and sulfide-based glasses include Ga-La-S-based and Ge-based glasses. BeF ₂ , ZrF ₄ , InF ₃ , etc.
And chalcogenide glasses such as As-S, As-Se, and Si-Te.

An optical waveguide according to the present invention focuses a laser beam having an energy amount causing a photoinduced refractive index change inside a glass material, and a continuous refractive index change region is formed inside the glass material. As described above, it is manufactured by relatively moving the focal point inside the glass material. In particular,
As schematically shown in FIG. 2, the laser beam 21 is condensed by a condensing device including a converging lens 22 and the like, and a converging point 23 is located inside the glass material 20. By moving the converging point 23 relatively inside the glass material 20, a continuous refractive index change region serving as the optical waveguides 24 and 25 is formed inside the glass material 20. The relative movement of the focal point 23 is, for example, a method of continuously moving the glass material 20 with respect to the focal point 23 of the laser light 21;
For example, a method of continuously moving the focal point of the laser light 21 inside 0 is adopted. The optical waveguide formed inside the glass material 20 is freely designed according to the relative movement of the light converging point 23. For example, when the converging point 23 is relatively moved in one direction, the optical waveguide 24 shown in FIG. 3 is formed. Also,
When the focal point 23 is relatively moved in two directions, a forked optical waveguide 25 shown in FIG. 4 is formed.

The change in the photo-induced refractive index is accelerated as the peak power intensity increases. However, it is practically difficult to obtain a laser beam having an excessively large energy amount. This point can be overcome by using a laser beam having a narrow pulse width and a high peak output. However, when pulsed laser light is used, the repetition frequency of the pulsed laser is preferably set to 10 kHz or more in order to make the optical waveguide formed inside the glass material smooth.

[0012]

The phenomenon in which the refractive index is changed by the irradiation of the pulse laser is called a photo-induced change in the refractive index.
Examples of silica glass to which Ge or the like is added are known. This phenomenon is thought to be due to the fact that oxygen vacancies having intrinsic absorption in the ultraviolet region exist in the glass, and part of the oxygen vacancies undergo structural change by irradiating a laser with an absorption wavelength. Research on excimer lasers whose wavelengths are in the ultraviolet region is ongoing. However, since the laser beam used in this method has a low repetition frequency of less than 10 kHz, sufficient energy cannot be given to the irradiated portion. Therefore, the shape of the refractive index change region becomes spot-like, and it is not possible to form an optical waveguide requiring a continuous change in the refractive index. Also, if the repetition frequency is forcibly increased in a state where the pulse width is constant, the energy per pulse decreases, and it becomes difficult to induce a change in the refractive index.

When the pulse width of the pulse laser is reduced, a high peak output can be obtained. If the peak output is increased in this way, even if pulsed laser light having a wavelength other than the intrinsic absorption of glass is used, the refractive index at the condensed portion of the laser light will be high regardless of the glass composition as long as it has a repetition frequency of 10 kHz or more. A changing phenomenon is confirmed. In order to form a smooth waveguide structure, it is necessary to narrow the pulse interval, in other words, to increase the repetition frequency so that the first pulse and the second pulse are irradiated in a period as short as possible. Also in this regard, the repetition frequency of the pulse laser is set to 10 kHz or more, preferably 100 kHz or more. When the repetition frequency is low, laser light is radiated discretely, and a continuous change in refractive index required for forming a waveguide cannot be obtained.

The upper limit of the repetition frequency is not limited to infinity but is close to that of a continuous laser. However, higher repetition frequencies generally result in lower energy per pulse. Therefore, in practice, the upper limit of the repetition frequency is set based on the threshold value at which the glass material changes the refractive index and the output of the laser used. When the repetition frequency is high, by continuously moving the laser or glass material relative to each other, a continuous refractive index change region is formed on the trajectory of the converging portion. This refractive index change region is used as an optical waveguide because it has a higher refractive index than glass before laser light irradiation. By reducing the scanning speed of the glass material or the focal point of the laser light, the glass material can be continuously irradiated with the laser light. However, since irradiation is performed in a state in which the second pulse overlaps at a certain time after the irradiation of the first pulse, the change in the refractive index formed by the first pulse is changed again by the second pulse, and a smooth waveguide structure is obtained. Can not be obtained.

According to the present invention, an optical waveguide having a desired shape can be easily obtained. Moreover, unlike the conventional manufacturing process, the laser light used for manufacturing the optical waveguide and the laser light source used for the nonlinear optical device can be shared, so that the work efficiency and the work speed can be increased. When a wavelength-variable laser light source is used, the wavelength for producing the optical waveguide and the wavelength for driving the nonlinear optical device can be changed. In addition, the nonlinear optical waveguide according to the present invention is excellent in optical characteristics such as a high polarization retention of linearly polarized light of the incident laser light since the cross section of the core portion is circular. Therefore, a nonlinear optical device such as an optical switch suitably used as a nonlinear optical element and configured using the same operates at high speed and high efficiency, and can be sufficiently used for practical use. In the following examples, a description will be given mainly of an optical waveguide produced by causing a change in refractive index (change in linear refractive index) in a nonlinear optical glass material by laser irradiation, and a nonlinear optical device using the same. However, the present invention is not limited to the embodiments at all, and it is needless to say that various modifications can be made without departing from the scope of the invention.

[0016]

EXAMPLE 1 Preparation of Optical Waveguide for Optical Car Switch PbO: 10 mol%, TiO ₂ : 10 mol%, TeO
₂ : 10% from tellurite glass having a composition of 80 mol%
A cubic test specimen of mm × 1 mm × 10 mm was cut out. Pulse width 150 fs, repetition frequency 200 kHz oscillated from a titanium sapphire laser excited by an Ar laser
Using a pulse laser beam having z, a wavelength of 0.8 μm, and an average output of 10 to 50 mW, the light was condensed by a condensing lens, and the test piece was irradiated with adjustment so that a condensing point was located inside the test piece.
Observation of the test piece after irradiation shows that the refractive index at the focal point is 0.0
Had risen by one. The change in refractive index occurred in a very short time, on the order of nanoseconds or picoseconds. By continuously moving the test piece or the condensing point relatively in one direction, a linear high refractive index region, that is, a linear optical waveguide was formed inside the test piece. The formation of the optical waveguide was confirmed by actually irradiating the test piece with laser light in the communication wavelength band and observing that the light was propagated only to the portion where the refractive index was changed. It was also found from the near-field image on the emission side that the cross section of the optical waveguide had a diameter (core diameter) of 4 μm and that single mode propagation was realized at least in the communication wavelength band.

Further, tellurite glass having a different composition,
An optical waveguide is formed by pure laser glass, silica-based glass doped with Ge, etc., phosphate glass, borate glass, fluoride glass, chloride glass, germanate, chalcogenide, etc. by similar laser irradiation. Confirmed that. Further, in the above example, 0.
Irradiated with laser light having a wavelength of 8 μm, other wavelengths,
For example, a similar change in the refractive index was observed when a laser beam having a wavelength of 1.3 μm or 1.55 μm in the communication wavelength band was irradiated. The diameter of the core of the optical waveguide was adjustable by changing the focal length of the condensing lens used. In the optical waveguide formed in this way, there is no clear interface between the core and the clad, so that the interface loss is extremely small. Therefore, the present invention is utilized as a method for forming a fine waveguide in an optical integrated circuit or the like.

Embodiment 2: Mach-Cheander type optical switch
Fabrication of Optical Waveguide for Switch The optical waveguide for a Mach-Cheander optical switch can be fabricated by various processes. For example, as schematically shown in FIG. 5, substrates 31 to 34 cut in advance are prepared, and only one substrate 31 is made of a highly nonlinear material such as tellurite, Three substrates 32-3
For 4, a material having low nonlinearity such as silica glass is used. After the optical waveguides 31a to 34a are formed by irradiating the respective substrates 31 to 34 with laser, the substrates 31 to 34 are bonded together with an optical adhesive. Alternatively, as schematically shown in FIG. 6, one substrate 35 having a predetermined size is used. The substrate 35 is made of glass having a small nonlinearity such as silica glass, and a material 36 having a large nonlinearity such as tellurite glass is provided on a partial surface of the substrate 35 by a sputtering method or the like. Next, the Mach-Cehnder type optical waveguide 35a is
Is written to. In any case, the operation of the fine moving table on which the substrates 31 to 15 are mounted causes the required shape of the optical waveguide 31a.
~ 35a are easily written.

In this embodiment, PbO: 25 mol%, Ti
Tellurite glass having a composition of O ₂ : 10 mol% and TeO ₂ : 65 mol% was used as a material having large nonlinearity, and glass made of 100% silica was used as a material having small nonlinearity. Pulse width 150 fs, repetition frequency 200 kHz oscillated from a titanium sapphire laser excited by an Ar laser
Using a pulse laser beam having z, a wavelength of 0.8 μm, and an average output of 10 to 50 mW, the light was condensed by a condensing lens, and the test piece was irradiated with adjustment so that a condensing point was located inside the test piece.
The refractive index at the focal point increased by 0.01 for tellurite glass and 0.005 for silica glass. In order to investigate the basic performance of the fabricated optical waveguide, when laser light in the communication wavelength band was actually incident on the optical waveguide, light propagation was observed only in the part where the refractive index change occurred, and single mode propagation was observed. It turned out to be realized. From the near-field image on the emission side, it was found that the formed optical waveguide had a core diameter of 4 μm. The size of the optical waveguide as a whole element was 10 mm × 1 mm × 20 mm.

Further, tellurite glass having a different composition,
Silica-based glass, phosphate glass doped with Ge or the like,
It was confirmed that an optical waveguide was formed by the same laser irradiation for glasses such as borate glass, fluoride glass, chloride glass, sulfide glass, germanate, and chalcogenide. On the other hand, as a material having a small nonlinearity, Ge with a small doping amount is used instead of pure silica glass.
A doped silica glass or the like could be used. It was confirmed that the optical waveguide obtained in the present example also had extremely low interface loss since there was no clear interface between the core and the clad.

Embodiment 3: Light for a directional coupler type optical switch
Fabrication of Waveguide An optical waveguide for a directional coupler-type optical switch can be fabricated in various steps as in the case of the Mach-Cheander type. For example,
As schematically shown in FIG. 7, the substrate 4 previously cut into four
1 to 44, a material having a large nonlinearity such as tellurite is used for only one of the substrates 41, and a material having a small nonlinearity such as silica glass is used for the remaining three substrates 42 to 44. use. Each substrate 41-
The optical waveguides 41 a to 44 44 are irradiated with laser light.
After forming a, the substrates 41 to 44 are bonded together with an optical adhesive. Alternatively, as schematically shown in FIG. 6, one substrate 45 having a predetermined size is used. Substrate 45
Is made of glass having a small nonlinearity such as silica glass, and a material 46 having a large nonlinearity such as tellurite glass is provided on a partial surface of the substrate 45 by a sputtering method or the like. Next, the directional coupler type optical waveguide 45a is written on the substrate 45 by laser irradiation. In any case, the optical waveguides 41a to 45a having the required shapes are easily written by operating the fine movement table on which the substrates 41 to 45 are mounted.

In this embodiment, PbO: 20 mol%, Ti
Tellurite glass having a composition of O ₂ : 5 mol% and TeO ₂ : 75 mol% was used as a material having large nonlinearity, and glass made of 100% silica was used as a material having small nonlinearity. Pulse width 150 fs, repetition frequency 200 kHz oscillated from a titanium sapphire laser excited by an Ar laser
Using a pulse laser beam having z, a wavelength of 0.8 μm, and an average output of 10 to 50 mW, the light was condensed by a condensing lens, and the test piece was irradiated with adjustment so that a condensing point was located inside the test piece.
The refractive index at the focal point increased by 0.01 for tellurite glass and 0.005 for silica glass. In order to investigate the basic performance of the fabricated optical waveguide, when laser light in the communication wavelength band was actually incident on the optical waveguide, light propagation was observed only in the part where the refractive index change occurred, and single mode propagation was observed. It turned out to be realized. From the near-field image on the emission side, it was found that the formed optical waveguide had a core diameter of 4 μm. The size of the optical waveguide as a whole element was 10 mm × 1 mm × 20 mm.

Further, tellurite glass having a different composition,
Silica-based glass, phosphate glass doped with Ge or the like,
It was confirmed that an optical waveguide was formed by the same laser irradiation for glasses such as borate glass, fluoride glass, chloride glass, sulfide glass, germanate, and chalcogenide. On the other hand, as a material having a small nonlinearity, Ge with a small doping amount is used instead of pure silica glass.
Doped silica glass, fluoride glass, and the like could also be used. It was confirmed that the optical waveguide obtained in the present example also had extremely low interface loss since there was no clear interface between the core and the clad.

Embodiment 4: Suitable for optical car shutter switch
An optical Kerr shutter switch was configured using the optical waveguide having a core diameter of 4 μm and a length of 10 mm manufactured in Example 1. FIG.
Denotes an optical system of the optical car shutter switch 50, and OP
1.30 μm wavelength titanium sapphire laser light (100f) passed through A (optical parametric amplifier)
s, 100 Hz) was used as a gate light P _g, and the light source 5
1, a wavelength of 1.32 μm synchronized with the gate light pulse,
A semiconductor laser beam having a pulse width 10ns emitted as the probe light P _i. The probe light P _i is inclined by π / 4 with respect to the polarization direction of the linearly polarized light of the gate light P _g by the λ / 2 wavelength plate 52, and the polarizer 53a, the mirror 54, and the lens 55a. To reach the optical waveguide 56.

In this optical system, a gate is provided by a mirror 54.
Light P_g And probe light P_i Becomes a collinear system (coaxial system)
The optical waveguide 56 is used as a Kerr medium.
It becomes possible. Probe light P_i Through the optical waveguide 56
After passing, the lens 55b, the filter 57, the analyzer 5
It is sent to the detector 58 via 3b. The detector 58 includes light
Electron multiplier, InGaAs-PIN photodiode, etc.
Is used. Gate light P_g Is blocked by the filter 57
And does not reach the detector 58. Note that, instead of the filter 57,
Alternatively, a spectroscope can be used. Gate light P_g No pa
Investigating the switching operation by adjusting the power
B light P_g The transmissivity T value of the equation T∝ sin^Two(n_2BLI_g)
Behavior as shown in FIG.
It was confirmed that it showed the operation of Phase change amount π
Was realized, and from this result, the tellurium used in this example was used.
Kerr constant n _2BIs 4.8 × 10^-15 cm^Two / W
It was calculated. No significant absorption in communication wavelength band, two light
There was no effect of offspring absorption. At a wavelength of 1.5 μm
A similar experiment is possible, and the
The change in the linear refractive index of the core itself due to light irradiation is also detected.
Was not. The laser power required for switching
Is about three orders of magnitude compared to the power required to fabricate an optical waveguide
A small one was enough.

In the present embodiment, the light source is a large titanium sapphire laser beam which has passed through the OPA. But,
Without being restricted by this, a small laser is used to gate light P _g
It is also possible to drive as. Further, a commercially available semiconductor laser used (wavelength 1.30 .mu.m, pulse width 10 ns, repetition frequency 150 MHz) as a gate light P _g, even with a probe light P _i by the semiconductor laser, the optical Kerr shutter operation is confirmed, the phase change The quantity π / 9 was achieved. This indicates that the optical system is greatly reduced in size. In the optical car shutter switch according to the present invention, by using a material having a larger nonlinearity,
The required gate light power can be reduced. For example, chalcogenide glass (As ₄₀ S ₅₇ Se ₃ , n _2B
= 1.3 × 10 ⁻¹³ cm ² / W), and an optical waveguide was produced in the same manner as in Example 1 except that the average irradiation power of the laser beam was 5 mW. The change in the refractive index in this case was 0.01. In the optical Kerr shutter switch incorporating this optical waveguide, the gate light power for the phase change amount π is 10
It was confirmed that the power was significantly reduced to 0 W or less.

The photomultiplier tube or PIN used in this embodiment
In a photodiode, its own response speed stops in nanoseconds. Therefore, by a general measurement method that delays the probe light pulse with respect to the gate light pulse,
The response speed of the optical car shutter switch was investigated. As a result of the measurement, the switching speed was equal to or less than the pulse width of the incident gate light, and it was confirmed that optical switching occurred due to the high-speed electron polarization effect. In addition, speed reduction due to two-photon absorption or thermal effect, speed reduction due to group delay dispersion, and the like were excluded. The optical car shutter switch employed in this embodiment has a switching speed of sub-picoseconds or less. Therefore, a modulation function of modulating the signal light at 100 GHz or more, a demultiplexing function of extracting an arbitrary signal pulse from a signal light pulse train having a repetition frequency of 100 GHz or more and converting it into a low-repetition pulse train, some low repetition light An optical car shutter switch having a multiplexing function or the like for multiplexing a pulse train into an optical pulse train of 100 GHz or more.

Embodiment 5: Mach-Cheander type optical switch
Core diameter 4μm prepared in Application Example 2 of the switch, built in the optical waveguide of length 10mm the Mach Chenda type optical switch, and subjected to optical switching experiments. In a Mach-Cheander type optical switch, first, laser light incident on one end of the element is split, and only one of the split light waves passes through a nonlinear medium. This light wave is given a phase shift by the nonlinear medium. After that, it is multiplexed again with the remaining light waves that have not been given a phase shift. At the time of multiplexing, output light obtained by modulating the original output light is obtained. In this embodiment, OPA (optical para
Using a titanium sapphire laser beam (100 fs, 100 Hz) having a wavelength of 1.35 μm that passed through a metric amplifier), a photomultiplier tube or an InGaAs-PIN photodiode was used as a detector. As shown in FIG. 11, which shows the results of the optical switching experiment, the output light, which was initially 80%, has been modulated by the third-order nonlinear optical effect, and as a result, has changed to 20%. You can see that it is. Further, there was no large absorption in the communication wavelength band, and no influence such as two-photon absorption was observed.
Further, a similar result was obtained in the wavelength band of 1.5 μm, and a change in the linear refractive index itself of the core due to irradiation with the gate light was not detected during the switching operation.

In the Mach-Cheander type optical switch of the present embodiment, if a material having a higher nonlinearity is used, the required laser light power can be reduced. For example,
In a Mach-Cheander type optical switch using chalcogenide glass (As ₄₀ S ₅₈ Se ₂ ) and incorporating an optical waveguide fabricated in the same manner as in Example 2 except that the laser beam having an average power of 5 mW is used, a required laser beam is used. It was confirmed that the power became 50 W or less. Note that the chalcogenide glass exhibited a refractive index change of 0.01 when irradiated with a laser beam having an average power of 5 mW. Regarding the response speed,
It was as fast as the optical car shutter switch.
Also in this case, a high-speed response was possible by the pure electron polarization effect, in which the slowing down due to two-photon absorption and thermal effects and the slowing down due to group delay dispersion were eliminated.

[0030]Embodiment 6: Directional coupler type optical switch
Application Light having a core diameter of 4 μm and a length of 10 mm manufactured in Example 3
The waveguide is integrated into a directional coupler type optical switch, and the optical switch is
It was subjected to a pitching experiment. The directional coupler type optical switch is
As shown in FIG. 12, the two waveguides 61 and 62 are sufficiently close to each other.
When it is attached, it is incident on one waveguide 61 (non-linear waveguide).
Light mode is coupled to the other, and the transmitted light
Energy transfer occurs, resulting in light energy from the exit end.
It uses the phenomenon that energy is turned on and off. Real truth
In this example, OPA (optical parametric amplifier)
1.32 μm wavelength titanium sapphire laser light passed
(100 fs, 100 Hz) using a photomultiplier tube or
InGaAs-PIN photodiode as detector
used. As can be seen from the test results in FIG.
Output P at output end of waveguide 61 ₁ Is initially 65%
However, coupling occurred due to the third-order nonlinear optical effect
As a result, it decreased to 55%. Conversely, the other waveguide 62
Output P at the output end of_Two Was initially 35%, but
It increased to 45% in some cases.

It can be seen from the changes in the outputs P ₁ and P _{2 that} the optical switching operation is occurring. Even in this case, there was no large absorption in the communication wavelength band, and no effect of two-photon absorption was detected. Similar results were obtained in the experiment in the wavelength band of 1.5 μm, and no change in the linear refractive index itself of the core due to gate light irradiation was detected during the switching operation. Also in the directional coupler type optical switch of the present embodiment, if a material having higher nonlinearity is used, the required laser light power can be reduced. For example, chalcogenide glass
In the directional coupler type optical switch incorporating (As ₄₀ S ₅₈ Se ₂ ) and incorporating an optical waveguide fabricated in the same manner as in Example 3 except that the laser beam having an average power of 5 mW is used, the required laser light power Was confirmed to be 150 W or less. The chalcogenide glass has an average power of 5 mW.
And a change in the refractive index of 0.01 when irradiated with the laser light. The response speed was also high as in the case of the optical car shutter switch. Also in this case, a high-speed response was possible by a pure electron polarization effect, in which a reduction in speed due to two-photon absorption or thermal effect and a reduction in speed due to group delay dispersion were eliminated.

[0032]

As described above, in the optical waveguide of the present invention, the optical waveguide in which the light-induced refractive index change region is continuously formed by condensing irradiation of laser light is written in the glass substrate. Therefore, an optical waveguide having a three-dimensionally complicated structure is easily formed. Moreover, the nonlinear optical device using this waveguide is used in the optical information processing and optical communication fields because it operates with high efficiency and has good optical characteristics. In addition, assuming a planar optical waveguide,
Unlike optical fiber type, PLC (Planar Lightwave Cir
cuit) and so on. Moreover,
The non-linear optical device according to the present invention utilizes a non-linear mechanism due to a pure electron polarization effect, so that high-speed operation of sub-picoseconds or less can be realized in a wide wavelength range including a communication wavelength band. Further, the optical waveguide and the nonlinear optical device using the same according to the present invention use not only the optical device utilizing the pure third-order nonlinear optical effect as described above, but also other nonlinear optical effects such as the secondary cascade effect. It can be diverted to an optical switch or the like.

[Brief description of the drawings]

FIG. 1 is a schematic view of an optical car shutter switch.

FIG. 2 is a diagram illustrating a method for manufacturing an optical waveguide according to the present invention.

FIG. 3 is an optical waveguide formed by one-way relative movement of a condensing point.

FIG. 4 shows an optical waveguide formed by bidirectional relative movement of a focal point.

FIG. 5 shows an example of a process for producing an optical waveguide for a Mach-Cheander type optical switch according to the present invention.

FIG. 6 shows another example of a process for fabricating an optical waveguide for a Mach-Cheander optical switch according to the present invention.

FIG. 7 shows an example of a process for manufacturing an optical waveguide for a directional coupler type optical switch according to the present invention.

FIG. 8 shows another example of a process for fabricating an optical waveguide for a directional coupler type optical switch according to the present invention.

FIG. 9 illustrates an optical system of an optical Kerr shutter switch incorporating the optical waveguide manufactured in the first embodiment.

FIG. 10 is a graph showing characteristics of the optical car shutter switch.

FIG. 11 is a graph showing characteristics of a Mach-Cheander type optical switch incorporating the optical waveguide manufactured in Example 2.

FIG. 12 is a diagram showing a relationship between an input and an output of an optical waveguide incorporated in a directional coupler type optical switch;

FIG. 13 is a graph showing characteristics of the directional coupler optical switch investigated in the sixth embodiment.

[Explanation of symbols]

10: Optical Kerr Switch 11: Polarizer 12: Analyzer 13: Nonlinear Refractive Index Medium (Kerr Medium) 20: Glass Material 21: Laser Light 22: Condensing Lens 23: Condensing Point 24, 25: Optical Waveguide 31-35 , 41-45: Substrates 31a-35a, 4
1a to 45a: optical waveguides 36, 46: material having large nonlinearity 50: optical Kerr shutter switch 51: light source 5
2: λ / 2 wavelength plate 53a: polarizer 53b: analyzer 54: mirror
55a, 55b: lens 56: optical waveguide 5
7: Filter 58: Detector 61: Non-linear waveguide 62: Normal waveguide

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kiyotaka Miura 1-13-22 Suzaku, Nara City, Nara Prefecture (72) Inventor Kazuyuki Hirao 3-5-8 Kizugawadai, Kizu-cho, Kizu-cho, Soraku-gun, Kyoto Prefecture

Claims (6)

[Claims] 1. An optical waveguide circuit wherein a glass material exhibiting a non-linear optical effect is used as a base or a part of the base, and a portion whose refractive index is changed by condensing irradiation of laser light is formed inside the base as an optical waveguide. 2. The optical waveguide circuit according to claim 1, wherein said substrate is made of oxide glass, halide glass, sulfide glass or chalcogenide glass. 3. The optical waveguide circuit according to claim 1, wherein the optical waveguide is bifurcated, and one of the branched optical waveguides is formed inside a glass material exhibiting a nonlinear optical effect. 4. An optical Kerr shutter switch, wherein gate light is incident on an optical waveguide together with incident light via a polarizer, and the incident light passing through the optical waveguide is extracted as output light via an analyzer. A nonlinear optical device using the optical waveguide circuit according to any one of the above. 5. An incident laser beam is demultiplexed, one of the demultiplexed lightwaves is passed through an optical waveguide made of a non-linear medium, a phase shift is given, and the other lightwave not given a phase shift is multiplexed. And a Mach-Cheander type optical switch for obtaining output light obtained by modulating input light.
A nonlinear optical device using the optical waveguide circuit according to any one of the above. 6. One of the two adjacent waveguides is a non-linear waveguide, and a light wave mode incident on one of the waveguides is coupled with a light wave mode incident on the other of the waveguides. A nonlinear optical device using the optical waveguide circuit according to any one of claims 1 to 3, in a directional coupler type optical switch for turning on / off light energy from an emission end due to transfer of transmitted light energy occurring in the optical waveguide circuit.