JPH04328725A - Nonlinear optical material and production thereof - Google Patents

Abstract

PURPOSE:To obtain a nonlinear optical material having high emission intensity from a shallow donor level, a high semiconductor content and a significant nonlinear optical effect. CONSTITUTION:Fine particles of CdS as a II-VI compd. semiconductor are dispersed in matrix glass contg. SiO2, B2O3 and ZnO as essential components or further contg. Al2O3, K2O and CaO and having 0.42, 0.90, 1.48, 2.00 or 2.40 molar ratio R of B to Si. When the molar ratio R is >=1, a nonlinear optical material having high emission intensity from a shallow donor level is obtd.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass nonlinear optical material in which fine particles of a group II-VI compound semiconductor are dispersed, which form the basis of an optical device utilizing a nonlinear optical effect, and a method for manufacturing the same.

0002

BACKGROUND OF THE INVENTION Conventional techniques include, for example, Journal of Optical Society of America, Vol. 73, p. 647 (J. Opt. Soc.
Am. Vol. 73 P. 647 (1983
)), as described in CdSx Se1-x
A cut-off filter glass in which the
Weight% composition: SiO2 68.9%, B2 O3 11
．． 5%, Al2O3 1.0%, ZnO11.3
%, CdSx Se1-x 0.6%, Na2O
5.6%, Sb2O3 1.1%) is used for nonlinear optical materials. This cut-off filter glass is produced by putting CdSx Se1-x and borosilicate glass raw materials in a platinum crucible and melting them at a high temperature of about 1600° C. or higher.

[0003] Also, Journal of Applied Physics, Vol. 63, p. 957 (J.
Appl. Phys. Vol. 63P. 957 (
There is a CdS fine particle dispersed glass thin film disclosed in 1988). This glass thin film was made using Corning's "7059 glass" (wt% composition: Si) as a target.
O2 49.9%, B2 O3 10.5%, Al2
O3 10.3%, BaO 25.1%, CaO
Using a quartz crucible containing CdS powder (4.3%), sputtering was performed with argon gas.
2 to 4% by weight of CdS is dispersed in "7059 glass".

0004

[Problems to be Solved by the Invention] In nonlinear optical materials that utilize the nonlinear optical effect of semiconductor fine particles,
Ultrafast response involving electrons and holes due to the quantum confinement effect can be expected, and the higher the content of semiconductor particles, the higher the nonlinear susceptibility can be expected. however,
In the conventional II-VI group compound semiconductor fine particle dispersed glass and its manufacturing method, the SiO2 content in the borosilicate glass matrix is high (for example, “CS2-5
9 glass” and “7059 glass”, B for Si
The molar ratios are 0.29 and 0.36, respectively. ) There were two problems as follows.

[0005] 1) In light emission from semiconductor fine particles, long-lived components are dominant. :The emission spectrum of semiconductor fine particle-dispersed glass includes light emission from shallow donor levels near the bandgap of the semiconductor, which has a short lifetime on the order of picoseconds, and deep levels caused by complex defects, which have long lifetimes on the order of nanoseconds. There is light emission from. Since the molar ratio of B to Si in the conventional glass matrix is small, the emission intensity of the former is much lower than that of the latter, which is not preferable for use in high-speed response devices.

2) When bulk nonlinear optical materials are manufactured by the melting method, the semiconductor content is small. : When manufactured by the melting method, it is melted at a high temperature of about 1600°C or higher, so
The semiconductor component decomposes and volatilizes, and there is a thermodynamic upper limit to the semiconductor content, which is about 1% by weight at most. Furthermore, when a thin film nonlinear optical material is manufactured by a sputtering method, the film is formed in a thermodynamically non-equilibrium state, so it is possible to contain a high concentration of semiconductor. However, in conventional sputtering methods, sputtering is performed using only argon gas, which can cause oxygen ions to be lost in the oxide glass matrix, or the composition of the sputter target to change during sputtering, resulting in a loss of stoichiometry of the semiconductor components. This tends to have an adverse effect on optical properties, especially in glasses with a low SiO2 content.

The present invention has a high emission intensity from a shallow donor level near the band gap, and therefore can be expected to be applied to devices that require ultra-high-speed response. It is an object of the present invention to provide a nonlinear optical material in the form of a thin film in which the stoichiometry is maintained in both the glass composition and the semiconductor fine particle composition.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the nonlinear optical material of the present invention comprises SiO2, B2O3,
It has a structure in which II-VI group compound semiconductor fine particles are dispersed in a glass matrix which contains ZnO and ZnO as essential components and has a molar ratio of B to Si of 1 or more. In addition, in the method of manufacturing a nonlinear optical material of the present invention, in the process of forming an oxide glass thin film in which II-VI group compound semiconductor fine particles are dispersed by a sputtering method, argon gas is
The method is characterized in that a gas forming the I-VI group compound semiconductor component and oxygen gas are mixed to perform sputtering.

[0009]

[Function] Since the nonlinear optical material of the present invention uses a glass matrix in which the molar ratio of B to Si is 1 or more, a small amount of B is mixed in the II-VI group compound semiconductor fine particles, which causes shallow donor levels. Because it increases the density of
Strong fluorescence with a lifetime on the order of picoseconds is emitted from this level. In addition, since the SiO2 content in the glass matrix is small, it can be melted at low temperatures even when manufactured by a melting method, so it is thermodynamically possible to contain a semiconductor at a high concentration.

[0010] Furthermore, in the method for manufacturing a nonlinear optical material of the present invention, in the process of forming an oxide glass thin film in which II-VI group compound semiconductor fine particles are dispersed by sputtering, argon gas is mixed with a gas that will become a semiconductor component and oxygen. Since sputtering is performed by mixing with a gas, it is possible to obtain a thin film-like nonlinear optical material in which the stoichiometry is maintained in both the glass composition and the semiconductor fine particle composition.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The glass matrix of the nonlinear optical material of the present invention contains SiO2, B2 O3 and ZnO as essential components, and has a composition in which the molar ratio of B to Si is 1 or more. Among the constituent components of this glass, SiO2 forms a strong glass skeleton and has excellent chemical durability and a low coefficient of thermal expansion. B2O3 not only lowers the melting temperature and the viscosity of the melt, but also mixes in a trace amount as B in the II-VI group compound semiconductor fine particles. ZnO prevents semiconductor components from volatilizing during melting, lowers the viscosity of the melt, and
Promotes diffusion of semiconductor components. In addition, melting temperature, viscosity,
Al2O to adjust chemical durability and thermal expansion coefficient
3, alkali metal oxides, alkaline earth metal oxides, etc. may be added.

[0012] By setting the molar ratio of B to Si to 1 or more, a small amount of B is mixed into the II-VI group compound semiconductor fine particles, which increases the density of the shallow donor level. It emits strong fluorescence with a lifetime on the order of picoseconds. In addition, since the SiO2 content in the glass matrix is small, it can be melted at low temperatures even when manufactured by a melting method, so it is thermodynamically possible to contain a semiconductor at a high concentration. Furthermore, since it can be manufactured by melting at a low temperature, the amount of volatile components is reduced, and a thin film-like nonlinear optical material can be obtained in which both the glass composition and the semiconductor fine particle composition maintain relatively stoichiometry. There is no particular restriction on the upper limit of the molar ratio of B to Si, but even if it is usually set higher than 3, it will improve the ratio of the emission intensity of emission from near the band gap to the emission intensity of emission from the target deep level. It is difficult for B2 O3 to become larger than that, making it uneconomical. If the B2 O3 component is too large, the water resistance may deteriorate, so 3 or less is usually sufficient.

There is no particular restriction on the amount of ZnO added, but it is 5-1% relative to the glass matrix component.
The content is preferably about 5% by weight. The II-VI group compound semiconductor fine particles to be dispersed include CdS,
CdSe, CdSSe, ZnS, ZnSe, etc. are preferable, and other semiconductor particles include CuCl, CuB
Metal halides such as r, PbI2, BiI3 are preferred.

In order to develop nonlinear optical properties, the particle size of the semiconductor fine particles dispersed in the matrix must be 100
It is preferably about angstroms or less, and the greater the content, the greater the nonlinear optical effect can be expected. Examples of the present invention will be described below.

Example 1 SiO2 :B2O3 :ZnO:Al in weight % composition
2 O3 :K2 O:CaO=x:67-x:15:
A nonlinear optical material was prepared in which CdS fine particles were dispersed in a matrix glass having a ratio of 4:10:4. Table 1 shows the values of x of the matrix glasses A to E produced and the molar ratio of B to Si (hereinafter referred to as R).

[0016]

[Table 1]

[0017] The production was performed according to the following procedure. Each of the glass raw material powders having the compositions A to E above and CdS powder are thoroughly mixed, placed in a platinum crucible, and melted at 1100 to 1300°C, then poured into a mold heated to around the respective glass transition temperature, and A sheet glass having a diameter of 1 mm was obtained. Immediately, this glass was heat-treated for 2 hours at a temperature 10° C. lower than each deformation temperature to grow CdS fine particles.

First, we investigated the maximum content of CdS in each glass, and found that it was 2% by weight in composition A, and the content increased as R increased, and it was possible to contain up to 6% by weight in composition E. . Below, characteristics were compared using samples containing 2% by weight. In any matrix composition, C
The average particle size of the dS fine particles is 30 angstroms,
The bandgap was blue-shifted by 0.7 eV compared to the bulk value, so after confirming that CdS was a quantum dot, the emission spectrum was measured.

FIG. 1 shows the relationship between R and the ratio of the intensity of light emitted near the band gap to the intensity of light emitted from deep levels (hereinafter referred to as P). From A to B is P
Although it hardly increases, when R exceeds 1, it increases rapidly, and in E, P reached more than 10 times that in A. In addition, in the sample containing 6% by weight of CdS with composition E, P was three times larger than in the sample containing 2% by weight.

[0020] In addition to CdS, as II-VI group compound semiconductor fine particles, CdSe, CdSSe, ZnS,
ZnSe could be dispersed, and when R was 1 or more, P rapidly increased. From the above, it was shown that the nonlinear optical material of the present invention has a high emission intensity near the band gap and a high content of semiconductor fine particles.

Example 2 A powder obtained by finely pulverizing the matrix glass having the composition E of Example 1 and CdS powder was mixed and then pressure-molded to a diameter of 10 mm.
A sputtering target with a diameter of 0 mm and a thickness of 2 mm was prepared. The CdS content in the target is 8% by weight.

[0022] Using a high frequency magnetron sputtering device,
Sputtering was performed using a mixed gas of Ar, O2, and H2S to form a CdS-containing glass thin film on a quartz glass substrate. The sputtering gas pressure was 2 x 10-2 Torr, and O
2 partial pressure and H2S partial pressure are each 0.5 to 2×10
-3 Torr, varied in the range of 0.5 to 5 x 10-3 Torr, there was no loss of oxygen ions in the matrix glass in this range, and the stoichiometric ratio of Cd and S was 0.98 to 1. A good quality thin film having a rating of 0.03 was obtained.

[0023] This was heat-treated at 350°C for 30 minutes, and Cd
Fine particles of S were grown. The CdS content was 8% by weight and the average particle size was 20 angstroms. The bandgap was blue-shifted by 1.2 eV compared to the bulk value, indicating that CdS was a quantum dot. In addition, strong light emission near the band gap was observed. On the other hand, when sputtering is performed using only Ar gas at 2 x 10-2 Torr, oxygen ions in the matrix glass are depleted and the film becomes black, which not only reduces the light transmission properties but also causes S to evaporate from the target over time. As a result, even the fine particles in the film lacked S, and the stoichiometric ratio decreased to CdS0.6 as the sputtering time passed.

[0024] In addition to CdS, ZnS, CdSe,
A high-quality glass thin film containing ZnSe fine particles could be produced by using H2S or H2Se as a sputtering gas in addition to Ar and O2. From the above, when mixing argon gas as a sputtering gas, a semiconductor component gas, and oxygen gas as in the present invention,
It is possible to obtain a thin film-like nonlinear optical material in which both the glass composition and the semiconductor fine particle composition maintain stoichiometry.

[0025] As the gas containing the elements constituting the semiconductor component, it is preferable to supply a gas containing a component that is particularly easily lost by evaporation or sublimation among the elements constituting the semiconductor component.

Example 3 The CdS microparticle-dispersed glass of composition E produced in Example 1 was polished to a thickness of 200 μm and sandwiched between two external mirrors to form a resonator to form an optical bistable device. Further, a similar optical bistable device was constructed using the 100 μm thick CdS fine particle dispersed glass thin film produced in Example 2.

Each of these elements has a wavelength of 398 nm.
, 344 nm laser light is incident with a spot diameter of 5 μm, and the relationship between the intensity of the incident light and the intensity of the emitted light is measured at room temperature (25°C).
), each exhibited bistable characteristics. From the above results, the nonlinear optical material of the present invention can be applied as a high-speed optical switch, and also has the effect of being applicable as an element applying other nonlinear optical characteristics.

[0028]

Effects of the Invention The present invention has a large emission intensity from a shallow donor level near the band gap, and a high concentration of II-VI.
A nonlinear optical material having a large nonlinear optical effect containing dispersed group compound semiconductor fine particles can be provided. Further, in the manufacturing method of the present invention, it is possible to provide a method for manufacturing a nonlinear optical material having good nonlinear optical effects in which both the glass composition and the semiconductor fine particle composition maintain stoichiometry.

[Brief explanation of drawings]

FIG. 1: Ratio P of the intensity of light emitted from near the band gap to the intensity of light emitted from deep levels and the molar ratio of B to Si in the glass matrix in the nonlinear optical material produced in Example 1 of the present invention. It is a graph showing the relationship with R.

Claims (2)

[Claims] [Claim 1] SiO2, B2 O3 and Zn
A nonlinear optical material comprising II-VI group compound semiconductor fine particles dispersed in a glass matrix containing O as an essential component and having a molar ratio of B to Si of 1 or more. 2. In the process of forming an oxide glass thin film in which II-VI group compound semiconductor fine particles are dispersed by a sputtering method, sputtering is performed by mixing a gas that will become a II-VI group compound semiconductor component with argon gas and oxygen gas. 1. A method for producing a nonlinear optical material comprising II-VI group compound semiconductor fine particles dispersed in a glass matrix.