JPH01179124A - Optical space modulating element - Google Patents

Abstract

PURPOSE:To execute a conversion processing at high speed and to miniaturize a device by using an element which has laminated a semiconductor element for outputting a voltage corresponding to intensity of light, and a semiconductor element in which transmittivity of light is varied in accordance with its output voltage. CONSTITUTION:As for an optical space modulation element 8, a first semiconductor element 11 for outputting a voltage in accordance with intensity of a modulated light 7, and a second semiconductor element 12 for varying transmittivity of light in accordance with its output voltage are laminated on a semiconductor substrate 10. According to such constitution, an image to be modulated 6 and the modulated light 7 are made incident through a window of the substrate 10, the element 11 outputs a voltage corresponding to intensity of the modulated light 7, the element 12 varies transmittivity in accordance with its voltage, the image to be modulated 6 is modulated by the modulated light 7, and an output image 9 is outputted. In such a way, since an electric field effect of photoabsorption in a semiconductor is utilized, the modulation processing is executed at high speed, and also, the element 8 can be miniaturized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical spatial modulation element that modulates the intensity of two-dimensional light such as an image by the intensity of another two-dimensional light. be.

[Conventional technology]

Conventionally, in order to modulate the intensity of two-dimensional light such as an image (hereinafter defined as a modulated image) by the intensity of another two-dimensional light (hereinafter defined as modulated light), it is necessary to A method was adopted that utilized changes in the polarization direction of the light. That is,
A control element that changes the polarization direction of the modulated image according to the intensity of the modulated light is placed between the polarizer and the analyzer, and the control element is irradiated with the modulated light that has been uniformly polarized by the polarizer. , the output light is output through an analyzer.

Figure 10 is an example of this, where (a) is a cross-sectional view and (b)
shows a front view. The operation of this element will be explained for one pixel. Since the modulated light A is irradiated onto the photoconductor 1 through the light-transmitting electrode 4, the conductivity of the photoconductor 1 increases as the intensity of the modulated light A increases. For this reason, electrode 4
The voltage supplied to the liquid crystal 3 via the photoconductor 1 and the transparent electrode 5 changes from . Therefore, the stronger the intensity of the modulated light A, the higher the voltage applied to the liquid crystal 3 sandwiched between the transparent electrodes 4.5.

In this case, the modulated image B input through the transparent material 2
When the light passes through the liquid crystal 3, its polarization direction is rotated by 90 degrees, and an output image C is output. By matching the polarization direction of the light passing through the polarizer and the polarization direction of the light passing through the analyzer, the intensity of the output light can be changed.

[Problem to be solved by the invention]

However, with this conventional method, both the writing time (the time it takes for the modulated light to affect the modulated image) and the erasing time (the time it takes for the modulated light to have no effect when the modulated light is turned off) are several numbers. There are problems in that it takes about 10 milliseconds and the device becomes large.

[Means to solve the problem]

In order to solve such problems, the present invention includes a first semiconductor element that outputs a voltage according to the intensity of light, and a second semiconductor element that is monolithically stacked on the first semiconductor element and outputs a voltage that corresponds to the intensity of light. Pixels are two-dimensionally arranged, each of which is made of a second semiconductor whose light transmittance changes depending on the change in light transmittance and which has a pin structure.

[Effect]

The output voltage of the first semiconductor element changes according to the intensity of the light irradiated to the first semiconductor element, and the transmittance of the second semiconductor element changes according to the voltage change, so that the modulated image is changed by the modulated light. Modulated.

〔Example〕

FIG. 2 is a diagram schematically showing the apparatus of the present invention, in which a modulated image 6 with an energy hν1 and a -like intensity and a modulated light 7 with an energy hν2 intensity are transmitted to a light spatial modulation element 8.
The input surface is overlapped with the input surface. The light spatial modulation element 8 modulates the intensity of the modulated image 6 for each pixel according to the intensity of the modulated light 7, and outputs the result as an output image 9. The output image 9 at this time is the modulated image 6 patterned with an intensity of energy hv1. Note that if the modulated light 7 is also patterned, optical logic operations can be performed between the modulated image and the modulated light.

FIG. 1(a) is a diagram showing the structure of the optical spatial modulation element 8 shown in FIG. 2. This is constructed by sequentially stacking on a semiconductor substrate 10 a semiconductor element 11 that outputs a voltage according to the intensity of modulated light, and a semiconductor element 12 that changes the transmittance of a modulated image depending on the applied voltage. The modulated image 6 and the modulated light 7 enter through a window 10a opened in the semiconductor substrate 10, but since the semiconductor element 11 outputs a voltage according to the intensity of the modulated light, the semiconductor element 12 outputs a voltage according to the intensity of the modulated light. The transmittance changes, and as a result, the modulated image 6 is modulated by the modulated light and output as an output image 9. At this time, when the semiconductor substrate 10 transmits the modulated image 6 and the modulated light 7, there is no need to provide the window 10a.
FIG. 1(b) is an example in which the order in which the semiconductor elements are stacked is reversed. In this case, if a window 1a is opened in the semiconductor substrate 1, an output image 9 is outputted through the window 1a.

FIG. 3 is a circuit diagram showing an equivalent circuit of an optical spatial modulation element, in which a photoconductive cell 13 is used as a semiconductor element that outputs a voltage according to the intensity of modulated light, and the transmittance of a modulated image is changed by an applied voltage. A pin structure semiconductor element 14 including a multiple quantum well layer as one layer is used as a semiconductor element. FIG. 3(a) shows the photoconductive cell 13 and the pin structure semiconductor element 1.
4 are connected in series, and they are connected to a constant voltage power supply 15. Here, the modulated image 6. It is assumed that the energies of the modulated light 7 are hν+ and hν2, and the energy band gap of the photoconductive cell 13 and the exciton absorption edge energy of the pin structure semiconductor element 14 are respectively Eg+ + Egg, and the following conditions are satisfied. .

hvz >Eg, >Egg >Fuh&11 In this way, the modulated light 7 influences the electrical conductivity of the photoconductive cell 13, and the modulated image light 6 is intensity-modulated by the pif structure semiconductor element 14. In other words, when the intensity of modulated light increases,
Since the electrical conductivity in the photoconductor 13 increases, pi
The reverse bias voltage applied to the n-structure semiconductor element 14 will increase. Then, in the pin structure semiconductor element 14, the exciton absorption edge energy shifts to the lower energy side. As a result, the absorption rate of the modulated image 6 in the pin structure semiconductor element 14 increases, so that the light intensity of the output image decreases. In this case, as the intensity of the modulated light 7 increases, the intensity of the output image decreases.

FIG. 3(b) shows an example in which a photoconductive cell 13 and a pin structure semiconductor element 14 are connected in parallel. The reverse bias applied to semiconductor device 14 is reduced. As a result, the pin structure semiconductor element 14
The transmittance of the modulated light 6 increases. therefore,
As the intensity of the modulated light 7 increases, the intensity of the output image can be increased.

FIG. 4 is a circuit diagram showing another embodiment. A photodiode 16 is used as a semiconductor element that outputs a voltage according to the intensity of modulated light, and a multi-quantum well layer is used as a semiconductor element that changes the transmittance of a modulated image depending on the applied voltage.
Quantum-Wel 1% or less defined as MQW)
A pin structure semiconductor element 14 including as an i-layer is used, and these are connected in series via a short-circuiting tunnel junction diode 16a. Here, the modulated image 6,
Let the energy of the modulated light 7 be hνl+”!, and the energy band gap of the photodiode 16, pin
The exciton absorption edge energy of the structural semiconductor element 14 is Eg+.

It is assumed that Egt has the following relationship.

hνt > E g ) > E g t > = hν
1 When such a relationship exists, the modulated light 7 changes the output voltage of the photodiode 16, and the modulated image 6 is intensity-modulated in the pin structure semiconductor element 14. That is, when the modulated light 7 is weak, the photodiode 16 is in an off state and the pin structure semiconductor element 14 is in a zero bias state, so the modulated image 6 is transmitted through the pin structure semiconductor element 14. On the other hand, when the modulated light 7 is strong, the photodiode 16 is turned on, so that a high reverse bias voltage is applied to the pin structure semiconductor element 14. pin
In the structural semiconductor element 14, the absorption of the modulated image 6 increases. Therefore, as the intensity of the modulated light 7 increases, the intensity of the output image decreases.

As described above, in the optical spatial modulation element, there are semiconductor elements such as photoconductive cells and photodiodes that output a voltage according to the intensity of modulated light, and pin structures that include a multi-quantum well layer as an i-layer. By combining this with an element that changes the transmittance of the modulated image depending on the applied voltage, the intensity of the modulated image can be modulated according to the intensity of the modulated light.

Figure 5 shows Ga prepared by molecular beam epitaxial method.
FIG. 2 is a diagram showing the structure of an As-type photoconductive optical spatial modulator for one pixel. This is a p-type GaAs substrate (thickness 200 mm
micron) AlGaAs/GaAs MQ on 17
Pin structure semiconductor element 14 (thickness 1 micron) including i-layer W structure, Ala, +Gao, J3 photoconductive cell 1
3 (thickness: 2 microns) are monolithically laminated. An output image window 17a was provided on the p-type GaAs substrate 17 by selective etching. Electrodes 18 and 19 were provided on the front surface of the photoconductive cell 13 and the back surface of the GaAs substrate 17 by gold vapor deposition. Furthermore, it was divided into 25 elements (5×5) by selective etching.

A front view and a cross-sectional view of this device are shown in FIG. 9. A light spatial modulation device 8 of 5×5 pixels formed on a 2 mm square GaAs substrate 17 is pre-deposited with gold pattern electrodes 20 and 21. It is adhered to a transparent glass plate 22 using conductive paint, and one pixel is 160 microns square, and the light receiving area and output area are 120 microns square. The electrodes 18 are interconnected over all pixels by connection lines 23 and further connected to the pattern electrode 20.

In the apparatus configured in this way, the modulated image has a wavelength of 854 nn+, an intensity of 200, and lj W/cm.
, uniform light of size 2IllI11 angles was used. The modulated light has a wavelength of 600 nm and a % intensity of 200 μW/cm.”
A patterned light having a brightness/darkness distribution with a % size of 21 angles was used.

These lights were irradiated onto the input surface of the optical spatial modulation element in a superimposed manner. Further, a constant voltage power source of 10 volts was connected between the electrodes.

The intensity of the output light at the pixel where the modulated light was in the bright state was half the intensity of the output light at the pixel where the modulated light was in the dark state. The response speed (writing speed, erasing speed) for one pixel was about 1 ns.

FIG. 6 shows one pixel of the structure of an InP-based photoconductive light spatial modulation element manufactured by metal organic vapor phase epitaxial growth. P-type InP substrate (thickness 200 microns) 17
A pin structure semiconductor element 14 (1 micron thick) including an InGaAsP/InP MQW structure as an i layer on a
, InP photoconductive cells 13 (thickness: 3 microns) are laminated in this order. Since the output image 9 is transmitted through the substrate 17a, no window is provided on the substrate. Note that the overall shape is similar to that shown in FIG.

The modulated image has a wavelength of 1300+v and an intensity of 200μ-/c.
The modulated light had a wavelength of 800 nm, an intensity of 200 μW, and a light-dark distribution of 70 m'', and the external bias voltage was 10 volts. The intensity of the output image at the pixel where the modulated light is in the bright state is two-thirds of the intensity of the output image at the pixel where the modulated light is in the dark state, and the response speed is 1
It was 0ns.

Figure 7 shows Ga prepared by molecular beam epitaxial method.
The structure of an As-type photovoltaic light spatial modulator is shown for one pixel. P-type GaAs substrate 17 (thickness 200 microns)
A pin structure semiconductor element 14 (thickness 1 micron) containing an AlGaAs/GaAs MQW structure as an i-layer on top, an AlGaAs tunnel junction diode 16a for shorting (
thickness 0.1 micron) and AI, 3caO,
tAspinAs Lumin photodiode 1 micron)
were stacked in order. An output image window 17a was provided on the substrate 17 by selective etching. Photodiode 1
Electrodes 18 and 19 were provided on the front surface of the substrate 6 and the back surface of the substrate 17 by gold vapor deposition. Note that the overall shape of the element is the same as that shown in FIG. 9 later.

With this configuration, a wavelength of 85 is used as a modulated image.
4 nm, intensity 200 IW/cm” (7) - using naked light, wavelength 600 nm, intensity 200 μW as modulated light
/cm" was used, and the external bias voltage was 10 volts. The intensity of the output image at the pixel where the modulated light is in the bright state is 2 times the intensity of the output image at the pixel where the modulated light is in the dark state. The response speed was approximately 1 ns.

FIG. 8 shows one pixel of the structure of an InP-based photovoltaic light spatial modulation element manufactured by metal organic vapor phase epitaxial growth. This is a p-type 1nP substrate 17a (thickness 2
00 micron) on InP GaAsP/InPMQW
It has a structure in which a pin structure semiconductor element 14 (thickness: 1 micron) including a structure as an i-layer, a short-circuiting 1nP channel junction diode 16a (thickness: 0.1 micron), and an InP pin photodiode 24 are laminated in this order. Since the output image is transmitted through the substrate, no window is provided on the substrate. The overall shape is the same as that shown in FIG.

In this configuration, a wavelength of 1 is added as a modulated image.
300 nm, intensity 200 μW/cm'' is used, and the modulated light has a wavelength of 800 nm and an intensity of 200 μW/cm.
cm'' brightness distribution was used, and the external bias voltage was 10 volts.The intensity of the output image at the pixel where the modulated light is in the bright state is 3/3 of the intensity of the output image at the pixel where the modulated light is in the dark state. 2, and the response speed was about 10 ns.

〔Effect of the invention〕

As explained above, the present invention provides Q CS E (Quantau+5-Confin
Since the electric field effect of light absorption in a semiconductor, such as the ed 5tarkEffect) effect, is utilized, the intensity of the modulated image is modulated by the modulated light, and the speed of the modulation process can be increased. Furthermore, optical spatial modulation can be performed with only one element, and that element can also be made smaller.

Therefore, it has the effect that optical spatial modulation can be performed with a relatively small and simple device configuration.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of the present invention, Fig. 2 is a schematic diagram for explaining the operation of this device, Figs. 3 and 4 are circuit diagrams showing equivalent circuits, and Figs. 5 to 8. 9 is a cross-sectional view showing the structure of one pixel, FIG. 9 is a view showing the overall configuration, and FIG. 1θ is a view showing an example of a conventional device. 1...Photoconductor, 2...Transparent substance, 3...
LCD, 4. 6. 18. 19... Electrode, 5...
...Transparent electrode, 6...Modulated image, 7...Modulated light, 8...Optical spatial modulation element, 9...Output image,
10... Semiconductor substrate, 11.12 semiconductor element, 13
... Photoconductive cell, 14 ... Pin structure semiconductor element, 15 ... Constant voltage power supply, 16 ... Photodiode, 16a ... Tunnel junction diode, 17
... p-type GaAs substrate, 20.21 ... pattern electrode, 22 ... transparent glass substrate, 23 ... connection line, 24 ... InP pin photodiode. Patent applicant: Nippon Telegraph and Telephone Corporation Agent: Kazuki Yamakawa (and 1 other person) 9 Figure 1 (Q) Figure 1 (b) Figure 9 (0) Figure 9 (1))

Claims (1)

[Claims] In an optical spatial modulation element that modulates information of a first light with information of a second light, the first and second semiconductor elements capable of transmitting at least a part of the irradiated light are monolithic. The first semiconductor element outputs a voltage according to the intensity of the irradiated light, and the second semiconductor element outputs a voltage according to the output voltage of the first semiconductor element. An optical spatial modulation element characterized by changing light transmittance and having a pin structure.