JPH02269307A - Face type optical modulator - Google Patents

Abstract

PURPOSE:To reduce the crosstalk between each element by providing a multi-layer structure formed by placing a multiple quantum well layer between two reflecting mirrors on a semiconductor substrate, and integrating a face type optical modulating element in which the reverse side of the semiconductor substrate is worked like a convex lens on the same semiconductor substrate like a two-dimensional matrix. CONSTITUTION:A multi-layer structure formed by placing a multiple quantum well layer 7 formed by laminating alternately two kinds of semiconductors whose band gaps are different from each other between two reflecting mirrors 3, 8 is provided on a semiconductor substrate 9, and a face type optical modulating element 12 in which the reverse side of the semiconductor substrate 9 is formed like a convex lens is integrated on the same semiconductor substrate 9 like a two-dimensional matrix. In this state, when a voltage is applied to electrodes 4, 5, that which is small in the absorption in the multiple quantum well layer at the time of non-electric field becomes large, and a switching operation for varying the transmission intensity of light can be obtained. By this switching operation, light transmits through the semiconductor substrate 9 and receives a condensing action by a lens 10, and condensed to a photodetector 13. In such a way, a face type optical modulator for reducing an optical crosstalk between each element can be obtained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to solid-state optical modulators.

[Conventional technology]

Conventionally, GaAs and GaAlAs have been used as planar light modulators.
Applied Physics Letters has developed a pin structure in which a quantum well layer consisting of alternately laminated thin films is sandwiched between contact layers made of p-type and n-type GaAlAs.
d) 'bysics Letters) Volume 44, 16
(1983), light incident on the surface passes through the quantum well layer and exits from the back side of the substrate. At this time, since the effective band gap decreases due to the application of an electric field, switching is performed by utilizing the fact that the absorption coefficient of the excitons in the quantum well for light on the low energy side increases.

[Problem to be solved by the invention]

However, the conventional planar light modulator described above is
When integrated into a dimensional matrix to form a solid-state optical modulator,
As shown in FIG. 2(a), the emitted light 20 undergoes diffraction and scattering, becomes light with a spread angle after being emitted from the solid-state optical modulator 12, and the emitted light 20 becomes light with a spread angle between adjacent solid-state optical modulators. There was a problem in that the elements overlapped with each other, worsening crosstalk between the elements.

The present invention aims to eliminate such crosstalk between each element.

[Means to solve the problem]

In the present invention, a multilayer structure is provided on a semiconductor substrate in which a multi-quantum well layer in which two types of semiconductors having different band gaps are alternately laminated is sandwiched between two reflective chains, and the back surface of the semiconductor substrate is formed in the shape of a convex lens. 2 solid-state light modulators
A planar optical transformer structure is adopted, which is characterized by being integrated on the same semiconductor substrate -E in a dimensional matrix.

[Effect]

The present invention has an optically nonlinear material having a multiple quantum well layer between two highly parallel Fabry-Béro resonators, so when a voltage is applied to the electrodes, there is no electric field. At times, the overlap of the wave functions of electrons and holes is small, so absorption in the multiple quantum well layer is small, but when an electric field is applied to the multiple quantum well layer, the wave functions of electrons and holes overlap. increases, absorption of incident light increases, and a switching operation that changes the transmission intensity of light can be obtained. In this case, since the light undergoes multiple reflections between the reflection chains, the optical path length in the multi-quantum well layer, which contributes to light modulation, becomes effectively longer and a greater contrast can be obtained.

The light emitted from the Fabry-Perot resonator section by the switching operation is transmitted through the semiconductor substrate 9 and is focused by the lens 10 formed on the semiconductor substrate 9, as shown in FIG. Since the light is focused on the light beam, crosstalk between each light modulation element can be eliminated.

Note that the reflective chain consists of a stack of semiconductor layers and dielectric layers, for example, 5 layers.
i02 and SiN are alternately stacked. Alternatively, it can be constructed by a commonly used method such as alternately stacking Si02 and a-St.

〔Example〕

FIG. 1 is a diagram showing an embodiment of a solid-state optical modulation element portion constituting a solid-state optical modulator of the present invention. This solid-state optical modulator is manufactured by the following procedure. First, a semiconductor multilayer reflective chain 8 is formed on a semiconductor substrate 9 made of n-type InP by metal organic vapor phase epitaxy. This semiconductor multilayer film reflective chain 8 is
N-type InP and n-type InGaAsP, which has lattice matching to rnP and has low absorption of incident light, are
50 pairs were alternately laminated with a thickness of /4 wavelength. Next, a multi-quantum well layer 7 is formed on the semiconductor multilayer reflective chain 8 . This multiple quantum well layer 7 is made of undoped InP.
, and undoped InGa lattice-matched to InP.
40 pairs of As were alternately laminated with a thickness of 100 layers each. After forming the multiple quantum well layer 7, a semiconductor layer 6 made of p-type InP is laminated thereon. After that, the semiconductor substrate 9 made of InP is polished to a thickness of about 100 μm, and a pattern in which circular photoresist films of 20 μm diameter are arranged in a two-dimensional matrix is formed on the polished surface by a photoresist process.
Cylindrical protrusions are formed on the semiconductor substrate by chemical etching, and after the photoresist film is removed, the semiconductor substrate is chemically etched again to form lenses 10 arranged in a two-dimensional matrix on the semiconductor substrate. This lens 10 becomes the exit window 1 of the solid-state light modulator, and the region of the semiconductor layer 6 located opposite to the exit window 1 becomes the entrance window 2, and the solid-state light modulators are arranged and formed in a two-dimensional matrix. That means that. A reflective chain 3 made of 5i02/a-Si is formed at the entrance window, and finally p-side and n-side electrodes 4 and 5 are deposited around the entrance window 2 and exit window 1, as shown in FIG. A solid-state optical modulator in which solid-state optical modulators are arranged in a two-dimensional matrix is completed.

〔Effect of the invention〕

According to the present invention, since the lens is formed in the exit window of the solid-state optical modulator integrated in a two-dimensional matrix, the second
As shown in Figure (b), since the emitted light 20 from each element is focused on each light receiving element 13 of the light receiving element array 11, a solid-state optical modulator with reduced optical loss talk between each element can be obtained. It will be done.

[Brief Description of the Drawings] Fig. 1 is a schematic cross-sectional view of one embodiment of a surface emitting modulator according to the solid-state optical modulator of the present invention, and Fig. 2(a) shows a conventional solid-state optical modulator using Figure 2 shows the spread of incident light when
Figure (b) is a diagram showing light condensation according to the present invention. 1... Output window, 2... Entrance window, 3... Reflection chain, 4
．． 5... Electrode, 6... Semiconductor layer, 7... Multiple quantum well layer, 8... Semiconductor reflective jii layer, 90.・Semiconductor substrate, 10... Lens, 11... Light receiving element array,
12... Solid-state optical modulator, 13... Light receiving element. Agent Patent Attorney Uchihara ShinmanzuyojPr Otsu

Claims (1)

[Claims] A planar type comprising a multilayer structure on a semiconductor substrate in which a multi-quantum well layer in which two types of semiconductors with different band gaps are alternately laminated is sandwiched between two reflective chains, and the back surface of the semiconductor substrate is processed into a convex lens shape. A planar optical modulator characterized in that optical modulating elements are integrated on the same semiconductor substrate in a two-dimensional matrix.