JP3225802B2 - Nonlinear optical material and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nonlinear optical material which forms the basis of an optical device utilizing a third-order nonlinear optical effect, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, non-linear optical materials have been considered for use as optical devices such as high-speed optical switches and harmonic generation elements. In particular, with regard to the semiconductor superlattice, metal fine particles, semiconductor fine particles or non-linear optical materials using organic compounds having non-linear optical properties, which are the core, development of higher-performance materials or more improved materials and their manufacturing methods attract attention. Have been.

As a conventional technique in this field, there is a nonlinear optical thin film disclosed in Japanese Patent Application No. 1-163056. This nonlinear optical thin film has a configuration in which a semiconductor superlattice is provided in a plurality of minute regions separated from each other on a substrate, and the other regions are embedded with a thin film of an insulator.

Also, Applied Physics A Vol. 47
As a conventional technique, a method for producing a glass in which fine gold particles are dispersed by a melting method described on page 347 (Appl. Phys. A, Vol. 47, 347 1988) can be mentioned.

[0005] This method is based on a melt-cooling method similar to the conventional method for producing a filter glass, in which gold dissolved in a glass matrix is further heat-treated to precipitate as gold fine particles.

[0006] Also, the Journal of Optical
Society of America Vol. 73, page 647 (J.
Opt. Soc. Am., Vol. 73 1983) uses a filter glass in which CdS _x Se _1-x is dispersed in borosilicate glass as a nonlinear optical material. This filter glass is made of borosilicate glass raw material and CdS
_x Se _1-x is put in a platinum crucible and melted at a temperature of about 1000 ° C. or more to produce it.

[0007]

The above-mentioned semiconductor superlattice,
Non-linear optical materials in which metal fine particles or semiconductor fine particles are dispersed have the following problems. (1) In the case of a semiconductor superlattice thin film: When the thickness of a well layer is one type, optical signal processing is possible only when light corresponding to the thickness of the well layer is used. Can not. Further, when a group II-VI compound semiconductor is used as a nonlinear optical material, a GaAs single crystal substrate is included in the structure, so that a light transmission type device cannot be manufactured. (2) In the case of metal fine particle dispersed glass: In the melt cooling method, the types of metals that can be melted are limited. Further, since the solubility of the metal in the glass is small, the amount of the metal dispersed can be increased only to about 10 ⁻⁶ to 10 ⁻⁵ volume%. In addition, the third-order nonlinear optical susceptibility is as small as 10 ^-13 to 10 ^-12 esu, and it cannot be said that the nonlinear optical characteristics are practically sufficient. Further, in order to precipitate the metal dispersed in the glass as fine particles, heat treatment must be performed at a high temperature of 1000 ° C. or more.
Furthermore, when one kind of metal is dispersed, optical signal processing can be performed only when light in the plasmon absorption region band of the metal is used, and multiplex signal processing cannot be performed. (3) In the case of semiconductor fine particle-dispersed glass: the melt cooling method has a problem that a part of the semiconductor constituents evaporates at the time of melting, and the composition of the semiconductor changes. In addition, the third-order nonlinear optical susceptibility is as small as 10 ^-12 to 10 ^-11 esu, which is not sufficient for practically sufficient nonlinear optical characteristics. Furthermore, when one kind of semiconductor is dispersed, a third-order nonlinear optical characteristic is manifested and optical signal processing is possible only when light in the absorption region band of the semiconductor is used. Can not.

According to the present invention, a multiple quantum well structure formed of a well layer and a barrier layer formed on a substrate and having at least two or more types of well layers having different thicknesses enables a multiplex capable of responding to light of a plurality of different wavelengths. It is an object of the present invention to provide a nonlinear optical material having a large third-order nonlinear optical susceptibility capable of signal processing.

Further, a GaAs single crystal substrate is formed.
In a multiple quantum well structure including a well layer and a barrier layer made of a II-VI compound semiconductor, a part of the substrate is removed,
By having a structure in which the removed portion is buried with at least one selected from glass, ceramics or II-VI compound semiconductor, it is possible to perform multiple signal processing capable of responding to light of a plurality of different wavelengths in a light transmission type structure. Big three
It is an object of the present invention to provide a nonlinear optical material having the following nonlinear optical susceptibility.

[0010]

In order to achieve the above object, a first nonlinear optical material according to the present invention comprises at least two or more types of multi-quantum well structures formed of a well layer and a barrier layer formed on a substrate. A non-linear optical material having a structure in which well layers having different thicknesses are formed, and the thickness of the well layer is in a region where electron and hole quantum levels are formed and electrons and holes are confined in the well layer. is there.

Further, the second nonlinear optical material of the present invention comprises:
This is a nonlinear optical material having a structure in which at least two or more types of well layers having different thicknesses are provided in a multiple quantum well structure including a well layer made of a II-VI compound semiconductor and a barrier layer on a ZnSe single crystal substrate.

Further, a third nonlinear optical material of the present invention comprises:
In a structure in which a GaAs buffer layer, a well layer composed of a II-VI compound semiconductor, and a multiple quantum well structure composed of a barrier layer are sequentially laminated on a GaAs single crystal substrate, a structure having at least two or more types of well layers having different thicknesses is provided. Is a nonlinear optical material.

Further, the fourth nonlinear optical material of the present invention comprises:
In a multiple quantum well structure comprising a well layer and a barrier layer comprising a II-VI group compound semiconductor formed on a GaAs single crystal substrate, a part of the substrate is removed, and the removed part is replaced with glass, ceramic or II-VI. It is a nonlinear optical material having a structure embedded with at least one selected from group-compound semiconductors.

Further, the fifth nonlinear optical material of the present invention comprises:
In a multiple quantum well structure formed of a group II-VI compound semiconductor well layer and a barrier layer formed on a GaAs single crystal substrate, the multi-quantum well structure has at least two or more types of well layers having different thicknesses. A non-linear optical material having a structure in which a portion is removed and the removed portion is embedded with at least one selected from glass, ceramics, and II-VI compound semiconductors.

In the above-described nonlinear optical material of the present invention, ZnSe is used for the well layer having a multiple quantum well structure, and ZnMg is used for the barrier layer.
It is preferable to use SSe. The embedded portion made of glass or ceramic is made of SiO ₂ , Ti
It is preferably at least one selected from O ₂ , Al ₂ O ₃ , and SiN. Further, it is preferable that the buried portion made of the II-VI compound semiconductor is at least one selected from ZnS and ZnSe.

Further, in the first method for manufacturing a nonlinear optical material according to the present invention, in a multiple quantum well structure formed of a well layer and a barrier layer formed on a substrate, at least two or more kinds of well layers having different thicknesses are formed by atomization. The structure is such that a barrier layer is formed by a molecular beam epitaxy method by a layer epitaxy method.

In a second method of manufacturing a nonlinear optical material according to the present invention, there is provided a multi-quantum well structure comprising a well layer made of a II-VI compound semiconductor and a barrier layer formed on a GaAs single crystal substrate. It has a structure in which a part of the substrate is removed and the removed part is buried with glass or ceramic by one method selected from a sputtering method, a sol-gel method, and a chemical vapor deposition method.

The third method of manufacturing a nonlinear optical material according to the present invention is directed to a multi-quantum well structure comprising a well layer made of a II-VI compound semiconductor and a barrier layer formed on a GaAs single crystal substrate. It has a structure in which a part of the substrate is removed and the removed part is buried with a II-VI group compound semiconductor by one method selected from a sputtering method and a chemical vapor deposition method.

[0019]

According to the first nonlinear optical material of the present invention,
In a multiple quantum well structure comprising a well layer and a barrier layer formed on a substrate, at least two or more types of well layers having different thicknesses are formed, and the thickness of the well layer forms quantum levels of electrons and holes, In addition, since the nonlinear optical material has a configuration in which electrons and holes are confined in the well layer, multiple signal processing capable of responding to light having different response wavelengths of light and thus responding to light of a plurality of different wavelengths is possible. A nonlinear optical material suitable for a reflection-type device having a large third-order nonlinear optical susceptibility can be achieved.

According to the second nonlinear optical material of the present invention, at least two or more kinds of thicknesses are provided in a multiple quantum well structure comprising a well layer made of a II-VI compound semiconductor and a barrier layer on a ZnSe single crystal substrate. Has a large third-order nonlinear optical susceptibility capable of performing multiple signal processing capable of responding to light having different response wavelengths of light and thus responding to light of a plurality of different wavelengths. A non-linear optical material suitable for a reflective device can be achieved.

According to the third nonlinear optical material of the present invention, the GaAs buffer layer and the II
-A non-linear optical material having a structure having at least two or more types of well layers having different thicknesses in a structure in which a multiple quantum well structure composed of a well layer composed of a group VI compound semiconductor and a barrier layer is sequentially laminated; A non-linear optical material suitable for a reflective device having a large third-order non-linear optical susceptibility capable of multi-signal processing capable of responding to light having different response wavelengths and thus a plurality of different wavelengths can be achieved.

Further, according to the fourth nonlinear optical material of the present invention, in the multiple quantum well structure comprising a well layer made of II-VI compound semiconductor and a barrier layer formed on a GaAs single crystal substrate, Is a non-linear optical material having a structure in which a part is removed and the removed part is embedded with at least one selected from glass, ceramics, and II-VI compound semiconductors, so that the multi-quantum well structure can be protected. Rather, the mechanical strength of the membrane is large,
A non-linear optical material suitable for a light transmission type device having a higher third-order non-linear optical susceptibility can be achieved.

Further, according to the fifth nonlinear optical material of the present invention, in the multiple quantum well structure comprising a well layer made of II-VI compound semiconductor and a barrier layer formed on a GaAs single crystal substrate, at least 2 It has a structure in which well layers having different thicknesses of different kinds or more are further removed, and a part of the substrate is removed, and the removed portion is buried with at least one selected from glass, ceramics or II-VI compound semiconductor. The nonlinear optical material not only protects the multi-quantum well structure, but also has a high mechanical strength of the film, and also enables multiple signal processing that can respond to light having different response wavelengths and, therefore, light having different wavelengths. Big 3
A non-linear optical material suitable for a light transmission type device having a non-linear optical susceptibility can be achieved.

The well layer of the multiple quantum well structure has ZnS
e. According to a preferred embodiment of the present invention in which ZnMgSSe is used for the barrier layer, ZnMgSSe has excellent lattice matching with a GaAs single crystal substrate, and has a larger exciton binding energy and a larger quantum confinement effect of ZnSe. It is possible to realize a nonlinear optical material having the following nonlinear optical characteristics.

The buried portion made of glass or ceramic is made of SiO ₂ , TiO ₂ , Al ₂ O ₃ , SiN
According to a preferred embodiment of the present invention in which the glass or ceramic is at least one selected from the group consisting of: Can be achieved.

Next, a first method for manufacturing a nonlinear optical material according to the present invention is a method of manufacturing a multi-quantum well structure comprising a well layer and a barrier layer formed on a substrate, wherein at least two or more kinds of well layers having different thicknesses are formed by atomic atomization. Since the barrier layer is manufactured by the molecular beam epitaxy method by the layer epitaxy method, the semiconductor composition and structure of the well layer can be precisely controlled, and a nonlinear optical material having a large third-order nonlinear optical characteristic can be obtained. It can be easily manufactured.

In a second method of manufacturing a nonlinear optical material according to the present invention, there is provided a multi-quantum well structure comprising a well layer formed of a II-VI compound semiconductor and a barrier layer formed on a GaAs single crystal substrate. This is a method in which a part of the substrate is removed and the removed part is buried with glass or ceramics by one method selected from a sputtering method, a sol-gel method, or a chemical vapor deposition method. Non-linear optical material suitable for light-transmitting devices that not only can protect the light but also have a large mechanical strength of the film and a large third-order nonlinear optical susceptibility capable of multiplex signal processing capable of responding to light of a plurality of different wavelengths. Can be easily manufactured.

Further, the third method for manufacturing a nonlinear optical material according to the present invention is directed to a multi-quantum well structure comprising a well layer made of a II-VI compound semiconductor and a barrier layer formed on a GaAs single crystal substrate. This is a method of fabricating a structure in which a part of the substrate is removed and the removed part is buried with a II-VI group compound semiconductor by one method selected from a sputtering method or a chemical vapor deposition method. A nonlinear optical material suitable not only for protection but also for a light transmission type device having a large mechanical strength of the film and a large third-order nonlinear optical susceptibility capable of processing multiple signals capable of responding to light of a plurality of different wavelengths. It can be easily manufactured.

[0029]

The present invention will be described more specifically with reference to the following examples.

The combination of the semiconductor used for the well layer and the barrier layer constituting the multiple quantum well structure is GaAs / A
III-V compound semiconductors such as l _x Ga _1-x As and GaAs / AlAs can be used, but ZnSe / ZnM
Group II-VI compound semiconductors such as gSSe and ZnCdS / ZnSSe are preferable because they can realize a nonlinear optical material having a large exciton binding energy and a large third-order nonlinear optical characteristic due to a quantum confinement effect. Also,
It is preferable that the number of well layers having different layer thicknesses is large because various types of wavelengths can be used.

The well layer of the multiple quantum well structure has
The thickness is such that the quantum confinement effect can be achieved. This depends on the type of semiconductor, but is preferably 20 nm or less.

The single crystal substrate forming the multiple quantum well structure is preferably a single crystal of GaAs, ZnSe, or InP which has high crystallinity and is easily lattice-matched with the multiple quantum well structure.

The multiple quantum well structure formed in this embodiment is preferably formed by atomic layer epitaxy, molecular beam epitaxy, or metalorganic molecular beam epitaxy because a structure having good controllability and good crystallinity can be produced. .

As a method of removing a part of the substrate in this embodiment, it is preferable to use a chemical wet etching method using an acid or an alkali because only the substrate can be removed without damaging the multiple quantum well structure. .

Hereinafter, specific embodiments of the present invention will be described. (Example 1) ZnS having the cross-sectional structure shown in FIG. 1 was formed on a ZnSe single crystal substrate using a normal molecular beam epitaxy apparatus.
A multiple quantum well structure composed of an e-well layer / ZnMgSSe barrier layer was manufactured. The Zn, Se, Mg, and ZnS raw materials were each placed in a cracker cell and heated to a temperature at which a molecular beam was generated, and the opening and closing time of the shutter of the cell was computer-controlled to form a well layer and a barrier layer sequentially. A multiple quantum well structure exhibiting the best characteristics at a substrate temperature of 300 ° C. was produced.

In FIG. 1, first, a ZnMgSSe barrier layer 8 having a thickness of 30 nm is formed on a ZnSe single crystal substrate 1, and then a ZnSe well layer 3 having a thickness of 20 nm is formed.
The well layer and the barrier layer 8 are repeatedly laminated in order, and the well layer 4 (10
nm), a well layer 5 (7 nm), a well layer 6 (5 nm), and a well layer 7 (2 nm).

FIG. 2 shows a photoluminescence spectrum at 12 K of the multiple quantum well structure in this embodiment.
In FIG. 2, the vertical axis represents the emission intensity of the spectrum as a relative value, and the horizontal axis represents the measurement wavelength. Although light emission from the ZnMgSSe barrier layer is observed even at 420 nm or less, here, five light emissions are observed, and light emission 9 is attributed to the well layer 7 (2 nm) from the short wavelength side, and light emission 10 corresponds to the well layer 6 (5 nm). ), Light emission 11 is in well layer 5 (7 nm), light emission 12 is in well layer 4 (10 nm), and light emission 13 is in well layer 3 (7 nm).
(20 nm), and well layers having five different layer thicknesses are formed. Further Measurement of the third-order nonlinear optical susceptibility in the reflection type disposed with laser corresponding to the respective wavelengths 1 × 10 ^-3
It was found to show a large value of ８8 × 10 ⁻³ esu.

Example 2 A ZnSe well layer having a cross-sectional structure similar to that of the first embodiment shown in FIG. 1 was formed on a ZnSe single crystal substrate by using an ordinary molecular beam epitaxy apparatus.
A multiple quantum well structure including a ZnMgSSe barrier layer was manufactured. Zn, Se, Mg, and ZnS raw materials were each placed in a cracker cell and heated to a temperature at which a molecular beam was generated, and a well layer and a barrier layer were sequentially formed by computer-controlling the opening and closing time of a shutter of the cell. During the growth of the well layer, the temperature of the substrate was set to 200 ° C., Zn was first deposited, and then Se was deposited to form a ZnSe monomolecular layer.
Was used to form a ZnSe layer by atomic layer epitaxy. When forming the barrier layer, the substrate temperature is set to 300
C. and formed by molecular beam epitaxy. The photoluminescence spectrum at 12K of the multiple quantum well structure in the present embodiment shows five emission peaks at the same positions as those shown in FIG. You can see that it is.
Further, in the present embodiment, the full width at half maximum of the peak was smaller than in FIG. Further, when the third-order nonlinear optical susceptibility was measured in a reflection type arrangement using lasers corresponding to the respective wavelengths, it was found that the terrestrial nonlinear optical susceptibility showed a large value of 4 × 10 ^{−3 to} 9 × 10 ⁻³ esu. In this example, it was found that the interface flatness and crystallinity of the multiple quantum well structure were higher than those of the first example. This is considered to be because the atomic layer epitaxy method was used to form the ZnSe well layer.

(Example 3) A GaAs buffer layer and a ZnSe well layer / Zn having the sectional structure shown in FIG. 3 were formed on a GaAs single crystal substrate by using a normal molecular beam epitaxy apparatus.
A multiple quantum well structure including a MgSSe barrier layer was manufactured. Zn, Se, Mg, ZnS, Ga and As were used as raw materials. Two connected vacuum chambers were used for film formation. First, Ga and As raw materials were each placed in a cracker cell on a GaAs single crystal substrate and heated to a temperature at which a molecular beam was generated to form a GaAs buffer layer of 1000 nm. After that, it is moved to the next vacuum chamber without exposing it to the atmosphere, Zn, Se, Mg, and ZnS raw materials are put into cracker cells and heated to the temperature at which molecular beams are generated, and the opening and closing time of the cell shutter is controlled by computer. Thereby, the well layer and the barrier layer were sequentially formed. The temperature of the substrate is 300 ° C. for both the buffer layer and the multiple quantum well structure.
Thus, a multiple quantum well structure exhibiting the best characteristics was produced.

In FIG. 3, a GaAs buffer layer 14 having a thickness of 1000 nm is further formed on a GaAs single crystal substrate 1, a ZnMgSSe barrier layer 8 having a thickness of 30 nm is formed, and a ZnSe well layer 3 having a thickness of 20 nm is formed. , A well layer and a barrier layer 8 are sequentially laminated to form a well layer 4 (10 n
m), a well layer 5 (7 nm), a well layer 6 (5 nm), and a well layer 7 (2 nm) were produced. The photoluminescence spectrum at 12K of the multiple quantum well structure in this embodiment is almost the same as that shown in FIG. 2, and it is understood that well layers having five different layer thicknesses are also formed in this embodiment. Was. Further Measurement of the third-order nonlinear optical susceptibility in the arrangement of the reflection type using the laser corresponding to the respective wavelength 2 × 10 ^-3 ~
It turned out to be as large as 9 × 10 ⁻³ esu. Further, in this example, it was found that the interface flatness and crystallinity of the multiple quantum well structure were higher than those of the first example. This is presumably because the GaAs buffer layer reduced unevenness on the substrate surface.

In this embodiment, the substrate is GaAs, but the same effect can be obtained by using ZnSe for the substrate.

(Embodiment 4) By a method similar to that of the above-described third embodiment, Ga having the cross-sectional structure shown in FIG. 3 was formed on a GaAs single crystal substrate by using an ordinary molecular beam epitaxy apparatus.
A multiple quantum well structure composed of an As buffer layer and a ZnSe well layer / ZnMgSSe barrier layer was manufactured. Further, after the GaAs single crystal substrate having the multiple quantum well structure having the structure shown in FIG. 3 is partially removed by etching using a sulfuric acid-based etchant, SiO ₂ is formed by a chemical vapor deposition method using silicon alkoxide as a raw material. In step 15, a non-linear optical material having a cross-sectional structure shown in FIG. 4, the numbers other than 15 indicate the same materials as those in FIG. The photoluminescence spectrum at 12K of the multiple quantum well structure in this embodiment is almost the same as that shown in FIG. 2, and it is understood that well layers having five different layer thicknesses are also formed in this embodiment. Was. Further, when the third-order nonlinear optical susceptibility was measured by a light transmission type forward-incidence degenerate four-wave mixing method using lasers corresponding to the respective wavelengths, a large value of 3 × 10 ⁻³ to 8 × 10 ⁻³ esu was obtained. It turned out to show. Further, in this example, it was found that the nonlinear optical characteristics can be measured even in the reflection type configuration, depending on the material used for embedding.

Further, using titanium alkoxide to form TiO
₂ or Al ₂ O ₃ using aluminum alkoxide
Was produced by a chemical vapor deposition method, and even when it was used in place of SiO ₂ 15, almost the same characteristics as above could be obtained.
Also, instead of SiO ₂ 15, Si was used by sputtering.
Even when N was used, almost the same characteristics as above could be obtained.

Further, by hydrolyzing the silicon alkoxide by the sol-gel method, a buried portion having characteristics equivalent to those of SiO ₂ 15 could be produced.

(Embodiment 5) In the same manner as in the fourth embodiment, a GaAs buffer layer and a 30 nm thick ZnMgSSe barrier layer were sandwiched on a GaAs single crystal substrate using a normal molecular beam epitaxy apparatus. A single well structure consisting only of a 5 nm thick ZnSe well layer was fabricated.
Further, after a GaAs single crystal substrate having a single well structure is partially removed by etching using a sulfuric acid-based etchant, a non-linear structure having a structure embedded with SiO ₂ by a chemical vapor deposition method using silicon alkoxide as a raw material. An optical material was produced. In the photoluminescence spectrum at 12 K of the single well structure in this example, one emission from the well layer was observed at 434 nm. In addition, 434n
When the third-order nonlinear optical susceptibility was measured by a light transmission type forward incidence degenerate four-wave mixing method using a laser of m
It was found to show a large value of 10 ⁻³ esu. Also,
In this example, it was found that the nonlinear optical characteristics could be measured even in a reflective configuration, depending on the material used for embedding.

(Embodiment 6) The same as in the above third embodiment.
Method, a normal molecular beam epitaxy on a GaAs single crystal substrate.
Ga having the cross-sectional structure shown in FIG.
As buffer layer and ZnSe well layer / ZnMgSSe failure
A multiple quantum well structure composed of a wall layer was fabricated. Furthermore, the figure
GaAs single crystal base having a multiple quantum well structure having the structure shown in FIG.
The plate is partially etched using a sulfuric acid-based etchant.
After the removal, diethyl zinc and hydrogen sulfide were used as raw materials.
Embedded in ZnS15 by chemical vapor deposition
A nonlinear optical material having a cross-sectional structure was fabricated. FIG.
, Each number other than 15 indicates the same material as that of FIG.
You. In the present embodiment, the multi-quantum well structure at 12K is used.
The photoluminescence spectra are as shown in FIG.
Approximately the same, and in this embodiment also five different layer thicknesses
It can be seen that a well layer consisting of was formed. further
Before the light transmission type using laser corresponding to each wavelength
-Order nonlinear optical susceptibility by degenerate four-wave mixing method
3 × 10^-3~ 7 × 10 ^-3esu and size
It turned out that it shows a suitable value. Also, in this embodiment,
Non-linear optics depending on the material used
It turned out that the characteristics could be measured. Also, diethylzine
Chemical vapor deposition using hydrogen and hydrogen selenide as raw materials
The buried portion may be formed of ZnSe instead of ZnS.
I was able to.

[0047]

As described above, according to the first nonlinear optical material of the present invention, at least two or more types of wells having different thicknesses in a multiple quantum well structure comprising a well layer and a barrier layer formed on a substrate. A non-linear optical material having a structure in which the quantum levels of electrons and holes are formed in the well layer and the thickness of the well layer is in a region where the electrons and holes are confined in the well layer. It is possible to provide a nonlinear optical material suitable for a reflection-type device having a large third-order nonlinear optical susceptibility capable of performing multiple signal processing and capable of responding to light having different response wavelengths of light and a plurality of different wavelengths.

According to the second nonlinear optical material of the present invention, at least two or more kinds of thicknesses are provided in a multiple quantum well structure comprising a well layer composed of a II-VI compound semiconductor and a barrier layer on a ZnSe single crystal substrate. Has a large third-order nonlinear optical susceptibility capable of performing multiple signal processing capable of responding to light having different response wavelengths of light and thus responding to light of a plurality of different wavelengths. A nonlinear optical material suitable for a reflective device can be provided.

Further, according to the third nonlinear optical material of the present invention, the GaAs buffer layer and the II
-A non-linear optical material having a structure having at least two or more types of well layers having different thicknesses in a structure in which a multiple quantum well structure composed of a well layer composed of a group VI compound semiconductor and a barrier layer is sequentially laminated; It is possible to provide a nonlinear optical material suitable for a reflection-type device having a large third-order nonlinear optical susceptibility capable of performing multiple signal processing capable of responding to light having different response wavelengths and thus a plurality of different wavelengths.

According to the fourth nonlinear optical material of the present invention, in the multiple quantum well structure comprising a well layer made of a group II-VI compound semiconductor and a barrier layer formed on a GaAs single crystal substrate, Is a nonlinear optical material having a structure in which a part of the structure is removed and the removed part is embedded with at least one selected from glass, ceramics, and II-VI compound semiconductors, thereby protecting the multiple quantum well structure. Instead, it is possible to provide a nonlinear optical material which is suitable for a light transmission type device having a large mechanical strength of the film and a large third-order nonlinear optical susceptibility.

Further, according to the fifth nonlinear optical material of the present invention, in the multiple quantum well structure comprising a well layer made of II-VI compound semiconductor and a barrier layer formed on a GaAs single crystal substrate, at least 2 It has a structure in which well layers having different thicknesses of different kinds or more are further removed, and a part of the substrate is removed, and the removed portion is buried with at least one selected from glass, ceramics or II-VI compound semiconductor. Non-linear optical material not only protects the multiple quantum well structure, but also enables high mechanical strength of the film, and multiple signal processing that can respond to light with different response wavelengths and thus multiple different wavelengths. It is possible to provide a nonlinear optical material suitable for a light transmission type device having a very large third-order nonlinear optical susceptibility.

The well layer of the multiple quantum well structure has ZnS
e. According to a preferred embodiment of the present invention in which ZnMgSSe is used for the barrier layer, ZnMgSSe has excellent lattice matching with a GaAs single crystal substrate, and has a larger exciton binding energy and a larger quantum confinement effect of ZnSe. A nonlinear optical material having the following nonlinear optical characteristics can be provided.

The embedded portion made of glass or ceramic is made of SiO ₂ , TiO ₂ , Al ₂ O ₃ , SiN
According to a preferred embodiment of the present invention in which the glass or ceramic is at least one selected from the group consisting of: Can be provided.

Next, according to the first method for manufacturing a nonlinear optical material of the present invention, in a multiple quantum well structure formed of a well layer and a barrier layer formed on a substrate, at least two or more types of well layers having different thicknesses are atomized. Since the barrier layer is formed by the molecular beam epitaxy method by the layer epitaxy method, it is possible to precisely control the semiconductor composition and the configuration of the well layer, and to obtain a nonlinear optical material having a large third-order nonlinear optical characteristic. Can be easily provided.

Further, the second method for manufacturing a nonlinear optical material according to the present invention is directed to a multi-quantum well structure comprising a well layer made of II-VI compound semiconductor and a barrier layer formed on a GaAs single crystal substrate. This is a method in which a part of the substrate is removed and the removed part is buried with glass or ceramics by one method selected from a sputtering method, a sol-gel method, or a chemical vapor deposition method. Optical material suitable for light-transmitting type devices having a large third-order nonlinear optical susceptibility capable of protecting multiple layers and having a large mechanical strength of the film and capable of responding to light of a plurality of different wavelengths and capable of performing multiple signal processing. Can be provided.

Further, the third method of manufacturing a nonlinear optical material according to the present invention is directed to a multi-quantum well structure comprising a well layer made of a II-VI compound semiconductor and a barrier layer formed on a GaAs single crystal substrate. This is a method of fabricating a structure in which a part of the substrate is removed and the removed part is buried with a II-VI group compound semiconductor by one method selected from a sputtering method or a chemical vapor deposition method. Large 3 that can be protected, has high mechanical strength of the film, and can respond to light of a plurality of different wavelengths and can perform multiple signal processing.
A non-linear optical material suitable for a light transmission type device having a non-linear optical susceptibility can be easily provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a nonlinear optical material according to an embodiment of the present invention.

FIG. 2 is a diagram showing an emission spectrum of a nonlinear optical material in an example of the present invention.

FIG. 3 is a schematic sectional view of a nonlinear optical material according to an embodiment of the present invention.

FIG. 4 is a schematic sectional view of a nonlinear optical material according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 multiple quantum well structure 3, 4, 5, 6, 7 well layer 8 barrier layer 9, 10, 11, 12, 13 light emission from well layer 14 GaAs buffer layer 15 embedded portion

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takao Nita 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-5-27283 (JP, A) JP-A-63 -177131 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02F 1/355 501 JICST file (JOIS)

Claims (9)

(57) [Claims] A non-linear optical material comprising a substrate and a layer having a multiple quantum well structure formed on the substrate and having a plurality of alternately stacked well layers and barrier layers, wherein the plurality of well layers are at least two layers. to have more kinds of different thicknesses, Oyo
And ZnSe as a material of the well layer and a material of the barrier layer.
A nonlinear optical material characterized by using ZnMgSSe as a material. 2. The method according to claim 1, wherein the thickness of the well layer is the thickness of a region in which quantum levels of electrons and holes are formed and the electrons and holes are confined in the well layer. Nonlinear optical material. 3. The substrate is a ZnSe single crystal substrate or GaAs.
3. The nonlinear optical material according to claim 1, wherein the substrate is a substrate having a GaAs buffer layer provided on a single crystal substrate. 4. A nonlinear optical material having a GaAs single crystal substrate, and a layer having a multiple quantum well structure in which a well layer and a barrier layer each composed of a II-VI compound semiconductor formed on the GaAs single crystal substrate are stacked. A part of the substrate is removed from the surface, and the removed part is embedded with at least one material selected from glass, ceramics, and II-VI compound semiconductors ; and
ZnSe, and ZnMgSSe as a material of the barrier layer.
Nonlinear optical material, which comprises using. 5. The nonlinear optical material according to claim 4, wherein a plurality of well layers and barrier layers are stacked, and the plurality of well layers have at least two or more different thicknesses. 6. A material to be embedded in a substrate partially removed from the surface is SiO ₂ , TiO ₂ , Al ₂ O ₃ , SiN,
ZnS, nonlinear optical materials 請 Motomeko 4 or 5, wherein you characterized by using at least one selected from ZnSe. 7. A substrate, the well layer and Zn using ZnSe
A method of manufacturing a nonlinear optical material having a step of forming a layer of a multiple quantum well structure by alternately laminating a plurality of barrier layers using MgSSe , and wherein the plurality of well layers have at least two or more different thicknesses A method for manufacturing a nonlinear optical material, wherein the well layer is formed by atomic layer epitaxy and the barrier layer is formed by molecular beam epitaxy. 8. Use of ZnSe on a GaAs single crystal substrate
Forming a layer having a multiple quantum well structure including a well layer and a barrier layer using ZnMgSSe, and removing a part of the substrate from the surface and embedding the removed part with glass or ceramics. A method for producing a material, wherein the glass or ceramic is embedded by one method selected from a sputtering method, a sol-gel method, and a chemical vapor deposition method. 9. A method using ZnSe on a GaAs single crystal substrate.
Forming a layer having a multiple quantum well structure including a well layer and a barrier layer using ZnMgSSe , and removing a portion of the substrate from the surface and embedding the removed portion with a II-VI compound semiconductor. A method for producing a nonlinear optical material, comprising: embedding the II-VI group compound semiconductor by one method selected from a sputtering method and a chemical vapor deposition method.