JP2002296627A - Optical switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical switch which is small, consumes low power, supports multichannel and is excellent in a quickly responding property. SOLUTION: The optical switch has two or more adjacent nonlinear optical elements with different transmittances. The transmittances of the nonlinear optical elements increase or decrease in response to intensity of an external field applied to the nonlinear optical elements. A position of a signal light radiated from the optical switch changes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical switch, and more particularly to an optical switch which is small in size, has low power consumption, supports multiple channels, and has excellent high-speed response.

[0002]

2. Description of the Related Art With the development of the information society using optical communication in recent years, it is necessary to construct a communication system capable of communicating a large amount of information at a high speed. Currently, WDM
(WDM) has been developed, and the speeding up of networks has been rapidly progressing.

[0003] An optical switch is indispensable for performing this optical system network at a higher speed.
Up to now, switching of optical information has required photoelectric conversion to convert optical information into electrical information once at a relay point. However, in order to solve problems such as an increase in power consumption and an increase in switching speed due to an increase in relay points, it is preferable to perform switching by light. For this reason, in the conventional optical switches, a mechanical optical switch, a planar optical waveguide optical switch, a mirror optical switch, a bubble type switch, and the like have been studied. (Nikkei Electronics No. 8, described in the January 29, 2000 issue.) However, in the above-described optical switch, since the switching time is about several milliseconds, it will correspond to the future large capacity and high speed of optical communication. Difficult. Further, the switching by the above-described method has a problem that an electric driving force required for the switching is large and energy consumption is still large. Therefore, as described in JP-A-11-337988, an all-optical switch having a high-speed response by light using a nonlinear optical material has been proposed.

[0004]

However, Japanese Patent Application Laid-Open No.
In the optical switch described in Japanese Patent No. 337988, two nonlinear optical materials are arranged and controlled by two different control lights, so that the entire device becomes large, and it is difficult to use the optical switch for miniaturization and multi-channel switching. . Further, the laser power required to induce the above-mentioned change in the refractive index is as large as about 5 to 50 MW / cm ^2, and there is a concern that the power consumption of the entire apparatus will also increase.

An object of the present invention is to provide an optical switch which consumes less power and is excellent in high-speed response in order to cope with miniaturization and multi-channel.

[0006]

In order to solve the above problems, an optical switch according to the present invention is an optical switch having two or more adjacent non-linear optical portions having different transmittances and / or reflectances, The transmittance and / or reflectance of these elements increase or decrease according to the intensity of the external field applied to these nonlinear optical parts, and the position of the signal light emitted from this optical switch changes.

The two or more nonlinear optical elements having different transmittances are made of the same nonlinear optical material, and have different optical path lengths of the signal light in the element.

Further, the optical switch according to the present invention comprises: an incident optical path for at least one signal light; an output optical path for two or more signal lights provided on the same plane as the incident optical path; A non-linear optical element provided between the outgoing light section and the incident light section of the outgoing optical path, and formed of a thin film material; and a substrate material supporting the non-linear optical element. Is disposed on the incident optical path, and has two or more adjacent portions having different film thicknesses on the optical path of the signal light of the thin film, and light is transmitted by an external field applied to the portions having different film thicknesses. The rate and / or reflectivity change,
The signal light passes through different output light paths according to the size of the external field.

In the above optical switch, the non-linear optical element is made of a thin film material whose transmittance and / or reflectance changes by changing the refractive index according to the intensity of the external field. The external field is a laser beam,
The intensity of the laser light is 0.5 MW / cm ² or less. Further, a transmittance adjusting layer is provided on the upper surface and / or the lower surface of the thin film material.

In the above optical switch, the nonlinear optical element is composed of a first metal oxide selected from Co, Fe, Cr, Ni, V and Si, Ti, Na, Ca, Al, T.
e, a crystal grain containing the first metal oxide as a crystal phase, and an amorphous grain boundary phase containing the first and second metal oxides. Including a thin film composed of The crystal layer of the first metal oxide is Co ₃ O ₄ .

[0011]

Next, embodiments of the present invention will be described in detail. (Example 1) First, for the basic study of the application of a nonlinear thin film material to an optical switch, first, a test piece of a single layer of a nonlinear thin film material was prepared, and a change in refractive index due to excitation light was examined. Figure 1
FIG. 2 shows a cross-sectional view of the single-layer thin film of this study. In FIG. 1, 1
Is a nonlinear optical thin film, and 2 is a substrate supporting this film.
Reference numeral 10 denotes excitation light for changing the refractive index, and reference numeral 11 denotes signal light. 12, a signal light source; 13, a signal light receiver; 14, 15, collimation lenses for collimating scattered light; 16, a polarizer; 17, an analyzer;
19 is a condenser lens.

In this experiment, a single-layer thin film composed of a cobalt oxide and a glass component was used as one nonlinear optical thin film.
Further, an SiO ₂ glass substrate was used as the substrate ₂ . Si
The size of the O ₂ glass substrate was 10 mm × 1 mm, and the thickness of the 1 nonlinear optical thin film was 50 nm.

The formation of the non-linear optical thin film 1 was performed using the rf sputtering method. A 6 ″ φ target obtained by mixing and sintering Co ₃ O ₄ and SiO ₂ .TiO ₂ at a weight ratio of 95: 5 was used as the target. The film was formed using Ar gas at a gas pressure of about 5 mTorr and power. Performed at 1 kW.

The wavelength of the thin film is 300 nm to 2000 nm.
2 is shown in FIG. Substrate transmittance was subtracted as background. This thin film has a tendency that the transmittance decreases as the wavelength becomes shorter, and has a transmittance of 90% or more at 1550 nm used for the communication wavelength, but gradually decreases from the visible light range of 800 nm. And
It decreased to about 80% at 650 nm and about 50% at 400 nm.

Next, in order to evaluate the nonlinearity of the thin film,
The change in refractive index due to laser light irradiation was measured. Excitation light 10 was irradiated on the film surface of the test sample shown in FIG. The excitation light has a pulse shape of 100 nanoseconds, and the laser power in the irradiation area is 0.05 MW / cm ^{2 to} 0.5 MW / cm ^2.
And The refractive index during irradiation with the excitation pulse light was measured by the signal light 11 incident from a direction of 45 ° on the sample film surface. In order to accurately measure the refractive index of only the excited area, the laser irradiation area of the excitation light 10 was set to 1.5 μmφ, and the measurement light irradiation area was set to 1.0 μmφ. Signal light 1
Reference numeral 1 designates an s-polarized light and a p-polarized light with respect to the sample, and a so-called ellipsometric optical system for measuring a refractive index based on a difference in reflectance between the p-polarized light and the s-polarized light by the nonlinear optical thin film 1 was used.

Although the wavelengths of the excitation light and the measurement light can be arbitrarily changed, in this measurement, a semiconductor laser of 650 nm whose oscillation drive control is easy was used as the excitation light source. The maximum output of this semiconductor laser was 20 mW. The measurement wavelength used was a 1550 nm laser used in communication and a semiconductor laser having the same wavelength as the excitation light. The measurement was performed with a laser power sufficiently weak to the excitation light intensity so that the sample was not excited by the measurement light.

FIG. 3 shows the change over time of the refractive index of the measurement light with respect to the incidence of the excitation laser light. In FIG. 3, the horizontal axis is time, and the pulse of the excitation laser starts rising from 0 seconds, and reaches a desired power after approximately 10 nanoseconds.
A decrease in the refractive index was observed following the rise of the excitation laser power, and the change in the refractive index was saturated approximately one nanosecond after the excitation laser light was saturated.

When the pump laser power was gradually increased, the saturated refractive index was gradually decreased. From this, the refractive index 10 nanoseconds after the saturation of the pulse light power was measured, and the pump light power dependency was measured. FIG. 4 is a schematic diagram showing a change in the refractive index when the nonlinear optical thin film is irradiated with excitation light. The refractive index without irradiation with excitation light is
The wavelength was 2.8 when the measurement wavelength was 1550 μm, and was 2.5 when it was 650 nm. However, at any wavelength, the refractive index decreased according to the change in the intensity of the excitation light, and 0.5 MW / c.
When this film was irradiated with light having an intensity of m ^2, the measured wavelength was reduced to 2.5 at 1550 nm and 2.2 at 650 nm.

Although not shown in FIG. 4, when the excitation light laser power was further increased, a further decrease in the refractive index was observed. When the excitation light power was 3 MW / cm ² , light was emitted at a measurement wavelength of 650 nm. Refractive index 2.0, 1550 nm
Then it fell to 1.9. However, the pump light power is 3MW / c
When it exceeds m ² , the film was deteriorated by the laser, which was not preferable.

From the above, it was found that the refractive index for various wavelengths changes when this thin film is irradiated with 650 nm excitation light. In particular, the transmittance is high in the communication wavelength band of 1550 nm, and the loss of light after passing through this thin film is small, which is effective. The laser intensity is 3MW
/ Cm ² or less, a large change in the refractive index was obtained without deterioration of the film. Further, the pump light laser power is set to 0.5 MW.
When the value is / cm ² or less, the power consumption of the entire optical switch system can be reduced, and switching can be performed by a high refractive index change, which is more preferable.

Next, a study was made to change the transmittance by utilizing the above change in the refractive index of the thin film. FIG. 5 shows a schematic diagram of a cross section of a thin film laminate using this thin film.
In FIG. 5, 1 is a nonlinear optical thin film, 3 is a transmittance adjusting film, and 2 is a substrate that supports them. The transmittance adjusting film No. ₃ was formed using SiO ₂ . This SiO ₂ thin film was formed by using rf sputtering as in the case of the first nonlinear optical thin film. Target size, deposition conditions, etc. are also 1
And the same as the nonlinear optical thin film.

The transmittance is measured by irradiating the excitation light laser 10 from a direction of 45 ° from the film surface of the laminate shown in FIG.
And the intensity I of the outgoing light with respect to the intensity I ₀ of the incident light of the signal light 11 was measured, and the transmittance was determined using the ratio I / I ₀ . The excitation light laser is 650 nm, which is the same as the study in FIG.
Semiconductor laser was used. The irradiation area on the sample is 1.5
μmφ. The power density is 0.05 to 0.5 MW / cm ²
And The wavelength of the measurement light was 1550 nm, and light having a diameter of 1.0 μmφ was transmitted in a region irradiated with the excitation light. Here, the total thickness of the nonlinear optical thin film 1 and the transmittance adjusting film 3 is the optical path length of light.

FIG. 6 shows the change in the transmittance of the signal light when the excitation light intensity is changed. The thickness of the nonlinear optical thin film is 50n
m, and when the thickness of the transmittance adjusting film was 100 nm (sample (A)), the transmittance when the excitation light was not irradiated was as large as 80%, but the transmittance was increased as the excitation light irradiation intensity was increased. The rate decreased, and when it was 0.5 MW / cm ² , it was as small as about 5%. This is considered to be because the refractive index of the one nonlinear optical thin film was changed by the irradiation of the excitation light, and the transmittance was lowered by interference with the transmittance adjusting film.

On the other hand, when the thickness of the non-linear optical thin film is 50 nm and the thickness of the transmittance adjusting film is 50 nm (sample (B)), unlike the case of sample (A), when the excitation light is not irradiated, The transmittance was almost 0%, and the amount of transmitted light increased as the intensity of the excitation light increased. And 0.5 MW / cm ²
At that time, it had a large transmittance of about 80%.

In the sample B, when the refractive index was not irradiated with the excitation light, interference occurred in the laminated film and the transmittance was low. However, since the refractive index was reduced by the irradiation of the excitation light, the interference condition was reduced. It is considered that the light transmittance was improved.

As described above, even when the thickness of the nonlinear optical thin film is the same, the transmittance can be adjusted according to the refractive index of each nonlinear optical thin film by changing the thickness of the transmittance adjusting film. there were. This indicates that the excitation light is ON or OFF.
Allows the signal light to be turned on and off. From the above, FIG.
By manufacturing a laminate having a film configuration as shown in (1), an optical switch for controlling the on / off of light can be obtained.

Further, an optical switch capable of changing the light emission position using this principle was manufactured. FIG.
8 and FIG. 8 show a plan view and an elevation view of the optical switch studied in the present invention. In these figures, 1 is a nonlinear optical thin film, 2 is a substrate supporting the nonlinear optical thin film, 3 is a transmittance adjusting film, 4 is an incident light path, 5, 5 'is an outgoing light path, and 6 is a 4,5 A cladding layer 7 is formed on the periphery, and 7 is a base for supporting the entire optical switch. Reference numeral 10 denotes an excitation laser light applied from the outside, and reference numeral 11 denotes a signal light that enters through an incident light path 4 and is output to the outside through an emission light path 5.

In FIG. 7, the portions composed of 1, 2, 3 are collectively called a nonlinear optical element 8. In this embodiment,
The nonlinear optical element has two surfaces with respect to the incident light path, and the two surfaces cover the outgoing light portion of the incident core portion. The thicker surface is called surface A, and the thinner surface is called surface B. The thickness of the nonlinear optical thin film on each of these two surfaces is equal, and the thickness of the transmittance adjusting film is different.

In this embodiment, as in the embodiment shown in FIG. 5, a thin film in which Co ₃ O ₄ and SiO ₂ .TiO ₂ are mixed at a weight ratio of 95: 5 is used as one nonlinear optical thin film. 3
SiO ₂ was used for the transmittance adjusting film. For 2, a glass substrate having a refractive index of 1.52 was used. The substrate size was 1 mm thick, 4 mm high, and 10 mm wide. The thickness of the non-linear optical thin film was set to 50 nm, and the thickness of the transmittance adjusting film was set to 100 nm on the side A and 50 nm on the side B so as to be the same as the embodiment shown in FIG.

In this embodiment, an optical fiber is used as the input optical path 4 and the output optical path 5. A glass substrate was used as the support 7 for the optical switch.

FIGS. 9 to 12 show a method of manufacturing this device. First, V-grooves for guiding the incident light path 4 and the output light path 5 were processed by a diamond dicer (FIG. 9). The depth d of the groove was 1 mm. Next, a groove 9 for inserting the nonlinear optical element (1, 2, 3) was processed (FIG. 10).
The groove had a depth d of 2 mm and a width t of 1.01 mm. 4,
For the groove processing of 5, 9, the shape of the dicer was made to match the shape of each groove.

Next, the substrate 2 on which the nonlinear optical thin film 1 is formed
A V-groove having a depth d: 0.3 mm and a width t: 1.2 mm was formed at the center of FIG. The surface of the groove was processed so as to be optically polished. After cleaning the grooved substrate 2, it was inserted into a sputtering apparatus. In the sputtering chamber, Co ₃ O ₄ −
_Two SiO ₂ and TiO ₂ targets and _two SiO ₂ targets
Inserted.

FIG. 12 shows a layout of a target and a substrate when each thin film is formed by a sputtering method. FIG.
In the figure, 2 is a substrate and 21 is a target.

At the time of substrate insertion, the substrate was arranged so that the substrate surface was parallel to the target, and a nonlinear optical thin film was first formed to a thickness of 50 nm by the method described above (FIG. 12A). Thereafter, the substrate was tilted in a vacuum chamber so that the angle θ of the substrate surface to the target surface was 60 ° (FIG. 1).
2 (B)). Then, the target was switched to SiO ₂ , and a film was formed so as to have a thickness of 100 nm in the portion A. By forming the film in this manner, the thickness of the transmittance adjusting layer on the portion B could be reduced to 50 nm.

The nonlinear optical element 8 thus formed is formed.
Was set on the support 7 prepared in FIG. The center of the V-shaped groove on the substrate 2 in FIG. 12 and the center of the V-shaped groove on the incident light path 4 formed on the support 7 were aligned with high precision. Thereafter, the incident light path fiber 4 having a diameter of 1 mm and the outgoing light path fibers 5, 5 'were set to produce an optical switch having the structure shown in FIG. The butted portion was filled with a resin that hardened at room temperature to prepare a one-to-two optical switch structure. At this time, the upper portion of the nonlinear optical element 8 was not buried in the resin.

In both the A and B sections, one excitation light 10
Was irradiated. In the case of the present embodiment, the excitation light 10 was irradiated from above in FIG. 7, that is, as shown in the sectional view of FIG. As the signal light 11, a semiconductor laser having a wavelength of 650 nm similar to that of the embodiment shown in FIG. 5 was used. Incident light path 4
Signal light having a wavelength of 1550 nm from the
The output light intensity output from 5 'was measured.

When the excitation light 10 is turned off, the intensity of light in the outgoing light path 5 near the surface A of the nonlinear optical element 8 is strongly observed, and the outgoing light 5 ′ in the light path close to the surface B is observed. Almost no light was observed from the optical path. From this, it can be determined that, when the excitation light is not irradiated, light is transmitted in the portion A, but light is not emitted in the portion B due to interference, and light was observed only from the emission optical path 5. Also, 0.5
On irradiation with the excitation light 10 of MW / cm ² , on the contrary, almost no transmitted light was observed from part A, and strong signal light was detected from part B.

From the above results, it was found that the signal light 11 can be switched by the pumping light 10 by installing the nonlinear optical element 8. Further, when the response speed due to the excitation light ON and OFF was detected, as shown in FIG.
It was confirmed that ON and OFF operations were performed at a response speed of nanosecond or less. (Embodiment 2) Next, the above embodiment was further developed to produce a multi-channel optical switch. FIG. 13 shows a top view of the multi-channel optical switch manufactured in this embodiment. In FIG. 13, 1 is a nonlinear optical thin film, 2 is a substrate supporting the nonlinear optical thin film, 3 is a transmittance adjusting film, 4
Is an optical path of the incident signal light, and 5 is an optical path of the output signal light. FIG. 14 shows a detailed view of FIG. The signal light 11 enters from the left side of the element and exits to the right side. The excitation light 10 is applied to each intersection between the nonlinear optical element and the optical path.

In order to irradiate each point with the excitation light 10, light irradiation was performed using a surface emitting laser. FIG. 15 shows a method of irradiating excitation light with a surface emitting laser. In FIG. 15, reference numeral 22 denotes a surface emitting laser. The light emitted from the surface emitting laser is applied to the branch point of each signal light. The surface emitting laser emits light so that the light travels in the direction to be branched. The emission timing of the surface emitting laser was determined based on the switching information written in the signal light.

In order to manufacture this multi-channel optical switch, a glass substrate was used as the substrate 2, a large number of V grooves were formed, and the grooves were mirror-polished. The film was formed by the same method as that shown in FIG. In this multi-channel optical switch, it is necessary to provide an optical path between each optical switch, and it is difficult to fabricate the optical path with a fiber-shaped optical path as shown in FIG. Therefore, an optical waveguide type optical path was manufactured.

This device was manufactured as follows. A core material in which SiO ₂ and GeO ₂ were mixed was formed on the substrate 2 by a flame deposition method. This is heat-treated to obtain a dense SiO
_A glass film made of ₂ and GeO ₂ was formed. Next, masking was performed on the glass film to provide an optical path as shown in FIG. 13, and portions not masked by lithography and etching were removed by etching. Next, the mask material was removed to form a waveguide having the same shape as the optical path in FIG. The width t of the waveguide was also 5 μm. The interval between the waveguides was set to 2.6 mm, and a waveguide for emission was formed at the center of the interval. Finally, the cladding layer 6 of SiO ₂ was formed by the flame deposition method, and a heat treatment was performed to form a dense glass layer.

Further, the boundary between the waveguides was removed by a dicer. The groove depth was 2 mm, which was the same as that of the device of FIG. Here, the nonlinear optical element 8 was inserted. Strict alignment was performed so that the groove formed in the element 8 coincided with the center of the core of the waveguide.

As described above, the multi-channel optical switch shown in FIG. 13 was manufactured. FIG. 13 shows a multi-channel optical switch in which the input and output optical paths are four rows each and three rows of nonlinear optical elements 8 are inserted. Using this optical switch, the positional relationship between the excitation light and the output light was examined. When a signal light was first inserted into the device without irradiating the excitation light, when the light was incident from a, the emitted light was observed from b '. Light incident from b was observed from c '. Further, when the portion indicated by c-1 was irradiated with excitation light and light was incident from c, emission light was also observed from c '. When c-1 and b-2 were irradiated with excitation light, emission light was observed from b '.

As described above, by irradiating the multi-channel optical switch of the present invention with the excitation light, the optical channel can be selected with high accuracy.

Although the embodiments of the present invention have been described with respect to the change in the refractive index of the excitation laser beam, the same change in the refractive index can be caused by heating the optical switch section by applying heat from the outside. Switching was possible. A change in the amount of transmitted light due to a change in the refractive index was also observed when a magnetic field or an electric field was applied.

Light switching was possible by changing the refractive index by applying an external field as described above.

Further, in this embodiment, the embodiment in which only the transmittance adjusting layer is formed on the upper surface of the nonlinear optical material has been described. The same light switching was possible in both cases.

In the above embodiment, the signal light is transmitted through the nonlinear optical thin film.
As shown in FIG. 1, good switching characteristics were also obtained when a reflection type optical switch in which excitation light was transmitted through the film and signal light was incident as reflected light on the film was produced. In the case of this reflection type optical switch, since the amount of reflected light changes due to a change in the refractive index of the nonlinear optical thin film, it was possible to completely block the signal light. (Embodiment 3) Next, the nonlinear optical thin film 1 described so far.
The composition of was studied in detail. The film configuration was the single-layer film shown in FIG. 1, and the amount of change in the refractive index due to excitation light irradiation was measured by the method shown in FIG.

Tables 1 to 3 show the film composition and sputtering conditions studied in the present invention, the refractive index (n ₀ ) at 1550 nm measured without irradiation with an excitation laser beam, and 6
The refractive index (n ₁ ) and the change in refractive index (Δn) at the same wavelength measured by irradiating an excitation laser beam of 50 nm are shown. The case where the absolute value of Δn is 15% or more is と き when the absolute value of Δn is 10% or more and less than 15%.
% When less than%.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

[Table 3]

In these tables, the composition indicates the target composition. The precipitated phase was identified by X-ray diffraction.

Samples Nos. 1 to 6 used a Co ₃ O ₄ target as a transition metal oxide raw material and S
It is a nonlinear optical thin film using a mixture of iO ₂ and TiO ₂ . The sputtering gas type was Ar, and the sputtering gas pressure was 3.
When the pressure is changed from 5 mTorr to 7 mTorr (Sample Nos. 1 to
3) The precipitated phase was Co ₃ O ₄ , and a change in refractive index of 10% or more was obtained, which was favorable.

On the other hand, in the sample formed by introducing oxygen into the sputter gas, the oxygen gas amount was about 1% like No. No.
Assuming that the oxygen gas amount is 5% or more as shown in FIG.
%, A very large change in refractive index was obtained.

When CoO was used as a raw material of the transition metal oxide, the change in the refractive index was less than 1% in Samples Nos. 7 to 9 formed of Ar, which was not good. Also in Sample No. 10 containing 1% of oxygen, the change in refractive index was small. In these samples, the precipitated phase was CoO
Therefore, it is considered that the amount of change in the refractive index was small. On the other hand, when the oxygen concentration is 5% or more, the sample No. 5,
As in the case of 6, a very large change in the refractive index could be obtained.

Samples Nos. 7 to 12 are examples in which SiO ₂ —Na ₂ O—CaO glass was used as the glass-based oxide, but Co ₃ O ₄ was deposited as in Samples Nos. 1 to 6. , A large change in the refractive index could be obtained. In particular, sample Nos. 17 and 1
When oxygen is contained at 5% or more as in 8, a particularly large change in refractive index can be obtained.

Samples Nos. 19 to 21 are examples in which TeO ₂ , Al ₂ O ₃ , and SiO ₂ were used as glass-based oxides. In each case, a film was formed with a sputtering gas containing 5% oxygen. As a result, a thin film in which a large change in the refractive index occurred could be obtained.

As described above, oxygen is introduced into the sputtering gas,
By using Co ₃ O ₄ as the precipitated phase, it is possible to obtain a nonlinear optical thin film in which a large change in the refractive index occurs. Also,
Instead of using CoO as a target material,
It is preferable to use ₃ O ₄ . Even when CoO is used, a thin film having a large nonlinear effect can be obtained by introducing oxygen gas.

As the glass component, SiO ₂ , SiO ₂
It has been found that a mixture of TiO ₂ and TiO ₂ , an oxide such as SiO ₂ —Na ₂ O—CaO-based glass, TeO ₂ , and Al ₂ O ₃ cause a nonlinear refractive index change.

Table 2 shows that the transition metal oxide is Co ₃ O ₄ ,
In this example, a mixture of SiO ₂ and TiO ₂ was used as a glass component, and the refractive index change of a sample formed by changing the composition ratio of Co ₂ and Co ₃ O ₄ was evaluated. As the content of Co ₃ O ₄ was decreased, the linear refractive index was gradually decreased, but the refractive index at the time of excitation was also decreased.

Δ for Co ₃ O ₄ composition obtained from Table 2
n is shown in FIG. When the Co ₃ O ₄ content was 30% by weight or more, the change in refractive index was 1% or more, and a change in refractive index that could be used for an optical switch could be obtained. Further, Co ₃ O ₄
When the content was 65% by weight or more and 95% by weight or less, the amount of change in the refractive index became 10% or more, and excellent characteristics could be obtained. Further, when the Co ₃ O ₄ content is 80% by weight or more and 9% by weight or more.
When the content was 3.5% by weight or less, the amount of change in the refractive index was 15% or more, and good characteristics could be obtained.

As described above, when the content of Co ₃ O ₄ is 30% by weight or more, a nonlinear optical thin film in which an optical switch can be manufactured can be obtained. And preferably may obtain a larger refractive index change not more than 95 wt% 65 wt% or more, more preferably Co ₃ O ₄ to 80 wt% or more content and a 93.5 wt% or less, a larger The amount of change in the refractive index is obtained.

In Examples shown in Table 3, types of transition metal oxides were examined. The transition metals are Cr, Fe, Ni,
V and a mixture of SiO ₂ and TiO ₂ as a glass-based oxide. Composition: 91% by weight of transition metal oxide
And the glass-based oxide was 9% by weight. In each of the thin films, a change in the refractive index similar to that of cobalt could be obtained. The change in the refractive index was close to 10%, which was good.

By using the nonlinear optical thin films having the compositions shown in Tables 1 to 3 to form the optical switch structures shown in Embodiments 1 and 2, it is possible to form optical switches having good switching characteristics. Was.

As a result of observation of the above nonlinear optical thin film by transmission electron microscopy, each thin film was composed of fine crystal grains identified by X-ray diffraction and an amorphous grain boundary phase surrounding the fine crystal grains. I was When the composition of the amorphous grain boundary phase was evaluated using energy dispersive X-ray fluorescence spectroscopy, the components constituting this crystal and SiO ₂ , TiO _2, etc. added as glass components were observed. . The crystal grains had a size of about 10 nm in each of the thin films.

Although the nonlinear optical section is formed in a V-shape in FIG. 7, the present invention is not limited to the V-shape. For example, a non-linear optical portion may be further formed between the A surface and the B surface, or a portion where a switch cannot be formed may be formed. That is, three or more nonlinear optical units may be formed, and the nonlinear optical units may not be adjacent to each other.

In the above-described embodiment relating to an optical switch having two or more adjacent nonlinear optical portions having different transmittances, the difference in transmittance due to the difference in the thickness of the nonlinear optical thin film is used. The transmittance may be changed by forming a thin film of a different material on the above-described nonlinear optical portion.

Also, an optical switch having a non-linear optical section having a different transmittance or an optical switch having a non-linear optical section having a different reflectance has been described above. The optical switch is useful because it can be applied to both transmission type and reflection type optical switches.

[0070]

As described above, the optical switch of the present invention has a thin film structure using a nonlinear optical thin film, and the laser power of the excitation light is as small as 0.5 MW / cm ² , so that the optical switch can be highly integrated. It is. Further, the optical switch of the present invention can be manufactured at low cost because the film formation method is easy.

Further, the optical switch of the present invention has excellent high-speed response, and thus has excellent switching characteristics for large-capacity information.

[Brief description of the drawings]

FIG. 1 is a diagram showing a method for evaluating optical characteristics of a nonlinear optical thin film of the present invention.

FIG. 2 is a diagram showing transmittance characteristics of the nonlinear optical thin film of the present invention.

FIG. 3 is a diagram showing a change in the refractive index of the nonlinear optical thin film of the present invention caused by pulsed laser irradiation.

FIG. 4 is a diagram showing a change in a refractive index with respect to a laser power.

FIG. 5 is a diagram showing a transmittance change test method using the nonlinear optical thin film of the present invention.

FIG. 6 is a diagram showing a change in transmittance with respect to laser power for transmittance adjusting films having different film thicknesses.

FIG. 7 is a top view of the optical switch of the present invention.

FIG. 8 is a side view of the optical switch of the present invention.

FIG. 9 illustrates a method for manufacturing an optical switch of the present invention.

FIG. 10 illustrates a method for manufacturing an optical switch of the present invention.

FIG. 11 illustrates a method for manufacturing an optical switch of the present invention.

FIG. 12 is a schematic view of a method for forming a nonlinear optical thin film and a transmittance adjusting film in a sputtering chamber.

FIG. 13 is a top view of the multi-channel optical switch of the present invention.

FIG. 14 is a detailed view of the optical switch of FIG. 13;

FIG. 15 is a schematic diagram of an excitation light irradiation method for the optical switch of FIG. 13;

FIG. 16 is a graph showing the amount of change in the refractive index when the composition of Co ₃ O ₄ is changed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Nonlinear optical thin film, 2 ... Substrate, 3 ... Transmittance adjustment film, 4
... Incoming optical path of signal light, 5 ... Outgoing optical path of signal light, 6 ... Clad part, 7 ... Support for optical switch, 8 ... Nonlinear optical element, 9 ... Insertion groove of nonlinear optical element, 10 ... Excitation light, 11
... Signal light, 12 ... Light source of signal light, 13 ... Receiver of signal light, 14, 15 ... Collimation lens, 16 ... Polarizer, 17 ... Analyzer, 18, 19 ... Condenser lens, 21 ... Sputter target, 22 ... surface emitting laser.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Takashi Naito 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture F-term in Hitachi Research Laboratory, Hitachi Ltd. 2K002 AA02 AB05 BA01 BA06 BA11 BA13 CA02 DA06 DA10 EA04 FA07 HA13

Claims (9)

[Claims] An optical switch having two or more adjacent non-linear optical portions having different transmittances and / or reflectances,
The transmittance and / or the reflectance of these elements increase or decrease according to the intensity of an external field applied to these nonlinear optical parts, and the position of the signal light emitted from the optical switch changes. Light switch. 2. The device according to claim 1, wherein the two or more nonlinear optical portions having different transmittances are formed of the same nonlinear optical material, and have different optical path lengths of the signal light in the element. Light switch. 3. An incident optical path for one or more signal lights, an output optical path for two or more signal lights provided on the same plane as the incident optical path, an output light part and an output light of these incident optical paths. A nonlinear optical element provided between the incident light portions of the path and made of a thin film material, and a substrate material supporting the nonlinear optical element, wherein the film surface of the thin film material is arranged on the incident light path. The thin film has an adjacent portion having two or more different thicknesses on the optical path of the signal light, and the light transmittance and / or the reflectance are changed by an external field applied to the portions having different thicknesses. An optical switch, wherein the signal light changes and the signal light passes through different output light paths according to the magnitude of the external field. 4. The optical element according to claim 1, wherein said nonlinear optical element is made of a thin film material whose transmittance and / or reflectivity change by changing its refractive index according to the intensity of said external field. 3. The optical switch according to any one of 3. 5. The optical switch according to claim 1, wherein said external field is a laser beam. 6. The optical switch according to claim 5, wherein the intensity of said laser beam is 0.5 MW / cm ² or less. 7. The optical switch according to claim 1, wherein a transmittance adjusting layer is provided on an upper surface and / or a lower surface of the thin film material. 8. The method according to claim 1, wherein the nonlinear optical element is Co, Fe, Cr,
A first metal oxide selected from Ni, V and Si, Ti,
A second metal oxide selected from the group consisting of Na, Ca, Al, and Te; a crystal particle having the first metal oxide as a crystal phase; and a non-crystal containing the first and second metal oxides. The optical switch according to any one of claims 1, 2, 3, 4, and 7, further comprising a thin film composed of a crystalline grain boundary phase. 9. The method according to claim 1, wherein the crystal layer of the first metal oxide is Co ₃ O ₄
The optical switch according to claim 8, wherein