JPH04104130A - Wavelength multiplexing optical element and image processing method using same - Google Patents

Abstract

PURPOSE:To realize high integration and low-input operation characteristics and to impose parallel optical logical modulation on the three primary colors of light by a single optical waveguide by varying the phase or refractive index of incident light by using specific plural layers of semiconductor thin films which differ in thickness, and performing light-intensity modulation, hue modulation, or the switching of a propagation path. CONSTITUTION:The layers (e.g. three layers) of semiconductor thin films which differ in layer thickness are included, and the respective semiconductor thin films have band gaps in the near infrared range and are sandwiched between barrier materials which has band gap outside the near ultraviolet range, thereby forming an optical waveguide 2 so that wavelengths of energy potentials in an electron-positive hole excitation state formed in the respective thin films of the layers correspond to specific visible light (red, green, and blue of visible light when the three layers are formed). Light beams which resonate with the respective energy potentials are made incident on the respective layers of this optical waveguide 2 and other light is used as modulating light or reference light to vary the phase or refractive index of the incident light, thereby constituting the wavelength multiplexing optical element so that the light intensity modulation, hue modulation, or the switching of the propagation path in an optional range of the visible light is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a wavelength multiplexing optical device used for light modulation, image processing, etc.

[Conventional technology]

Conventionally, nonlinear optical functional elements have been proposed that have functions of performing optical modulation, optical frequency conversion, etc. using nonlinear optical effects in optical waveguides. Regarding its operating characteristics, for example, "Journal of Applied Physics, Vol. 58 (1)
985), pages R57 to R78 (J, APρ1
．． Phys.

58 (L985), pp, R57-R78)J. In the above literature, in an optical waveguide under the condition that light of a single wavelength is guided, optical modulation is performed using a change in refractive index due to a nonlinear optical effect, and second harmonic generation is generated due to a second-order nonlinear optical effect. Optical frequency conversion has been attempted. The refractive index change due to the nonlinear optical effect is about 10%, and the length of the optical waveguide is about 1 cm. Further, a pulse laser with an output of about 100 W is used as a light source.

[Problem to be solved by the invention]

The above-mentioned conventional technology has problems such as the large size of the element to realize the function, the low degree of integration, and the need for a high-output light source. It is difficult to construct the device. Further, in the above-mentioned conventional technology, it is difficult to process the three primary colors of light in parallel using one optical waveguide, or to compare two images to recognize common parts.

An object of the present invention is to have the characteristics of high integration and low input operation, and to be able to perform optical logic modulation operations in parallel with a single optical waveguide for the three primary colors of light, or to perform image processing using natural colors. An object of the present invention is to provide a wavelength multiplexing optical device capable of performing the following steps.

[Means to solve the problem]

The above object includes a semiconductor thin film of multiple layers (for example, three layers) each having a different thickness, and the semiconductor thin film is sandwiched between barrier materials having a band gap in the near-infrared region and a band gap in the near-ultraviolet region. By being
The energy level of the excited state of electrons and holes formed in the thin film of each layer has a wavelength of visible light (for example, in the case of three layers).

An optical waveguide is formed to correspond to visible light (red, green, blue), and light that resonates with each energy level is input to each layer of the optical waveguide, and other light is used as modulated light or reference light. This is achieved by configuring a wavelength multiplexing optical element to change the phase or refractive index of the incident light by irradiating it as Ru.

[Effect]

In the above configuration, when light having a wavelength that resonates with the exciton level is incident, polaritons are formed by coherent interaction between the exciton and the light. When polaritons are present, the interaction between excitons and light is extremely strong, and the refractive index of the medium at the resonant wavelength increases significantly compared to the value in air. In particular, when a quantum well structure is constructed using a material with a much larger bandgap than a semiconductor thin film quantum well layer for the barrier layer, the interaction between excitons formed in the quantum well and light becomes even stronger, leading to a resonance state. The refractive index in the atmosphere is more than 10 times that in air. Such a situation is, for example, Z nSD, , S'e, 1. GaAs
This can be realized by using a ■-■ group compound such as the following as a quantum well. In this system, the lattice mismatch is also 0.42%
It can be said that there is no such thing as , so the influence of distortion can be ignored.

When using the above system, since the refractive index is 10 or more for light with a wavelength in the resonance region, it is possible to guide light into an optical waveguide with a width of nanometer size, and the integration of optical devices can be improved. can be dramatically increased. In addition, since the band gap of the barrier layer is in the near-ultraviolet region and the band gap of the quantum well layer is in the near-infrared region, changing the thickness of the quantum well causes the wavelength of light that resonates with the quantum well excitons to change over the entire visible light range. It is variable. Therefore, by providing three quantum well layers with different thicknesses,
Polaritons corresponding to red (R), green (G), and blue (B), respectively, can be propagated through a single optical waveguide. These R, G, and B are the three primary colors of light, and an element that guides natural colors and performs optical calculations can be constructed.

In addition, by utilizing the fact that the phase of polariton changes due to exciton scattering, an interference type optical waveguide is constructed, and the electron-hole system created by modulated light changes the phase of polariton formed by input light. By changing the interference conditions, the intensity of light can be modulated. In this case, since the exciton component of the polariton is highest at the exciton resonance wavelength, scattering becomes stronger when the wavelength of the modulated light is close to that wavelength.

Therefore, by selecting the wavelength component of the modulated light, it is possible to modulate any component among R, G, and B, and it is possible to modulate the color tone,
It can be applied to wavelength multiplexing logic, etc. Note that the intensity of the modulated light necessary to produce this effect is only about 1 mW, and this has the advantage that it is possible to configure an element that operates with low input.

Furthermore, exciton scattering weakens the interaction between excitons and light,
Decrease the refractive index. Therefore, by irradiating the optical waveguide with light and inducing exciton scattering, the confinement of light in the optical waveguide is weakened, and by increasing the leakage of the electric field of light to the outside, its components are It can also be taken out to another optical waveguide provided. This enables RGB image processing, as shown in Example 2 below, and allows comparison between the original image and the reference image in natural colors according to the wavelength components of the reference light. In this case, as in the above modulation, the intensity of the reference light may be about 1 mW.

Note that the device according to the present invention uses interaction between excitons and light using polaritons as described above;
In order to fully exhibit this effect, it is necessary to take structural consideration so that when light is incident on the quantum well layer, the light is incident in the longitudinal direction of the layer.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

Example 1: In this example, an optical waveguide for inputting modulated light is connected to a part of the Matsuharzender interferometer optical waveguide, and red (R), green (
This is an example in which an element is configured to waveguide and modulate the three primary colors of light, G) and blue (B). FIG. 1(a) shows a schematic appearance of the Matsuharzender interferometer of this example, and FIG. 1(b)
) shows the configuration of the optical waveguide (illustrated horizontally).

First, the manufacturing method will be described. In FIG. 1(b), a semi-insulating GaAs wafer is used as a substrate 1, and an undoped GaAs wafer is first formed on the substrate 1 as a cladding layer 4.
A s is 1.0 μm, and Z n S becomes the barrier layer 8.
11*1s S eo @86 to 1.5μm, 19.8
GaAs quantum well layer 5,100 barrier layer 8.1
1.3 GaAs quantum well layer 6,100 barrier layer 8.8.5 GaAs quantum well layer 7.1.5 μm barrier layer 8 and then cladding layer using molecular beam epitaxy (MBE method) Epitaxial crystal growth is performed by

The cladding layer 4 and the region sandwiched therebetween serve as the core. In the quantum well layer 5, an exciton level 9 is generated which becomes a source of red-band polaritons. Exciton level 9 at liquid helium temperature
The energy is 1.77 eV and the wavelength is 707 nm. Furthermore, the exciton level 10 of the quantum well layer 6 corresponding to the green band polariton has an energy of 2.30 eV and the wavelength of 542 nm, and the exciton level 11 of the quantum well layer 7 corresponding to the blue band polariton: Energy is 2.89e
V, the wavelength is 430 nm.

After crystal growth, contact mask exposure is performed to produce the image shown in Figure 1 (
Process it into a Matsuharzender interferometer as shown in a). Here, the convergence of the optical waveguide is 4 μm, the length of the interferometer is 200 μm, and the lengths of the optical waveguides connected to both ends of the interferometer are each 25 μm, so the interferometer optical waveguide 2
The total length of is 250 μm. Further, the length of the modulated light input optical waveguide 3 connected to a part of the interferometer is 100 μm.

The above elements are cooled with liquid helium, and each wavelength is 7.
R incident light 21 with wavelengths of 07 nm, 542 nm, and 430 nm
, G incident light 22 and B incident light 23 are input to the interferometer optical waveguide 2. Then, each incident light resonates with the corresponding quantum well exciton, and propagates as R-band, G-band, and B-band polaritons. Here, R, G with wavelengths of 707 nm, 542 nm, and 430 nm are provided in the optical waveguide 3 for modulated light incidence.
, and B light as modulated light 41, 42.43, the interference conditions change because the phase of the polariton of the resonant wavelength changes, and the R, G, and B outgoing lights 31, 32, 33
The intensity of changes. Therefore, R incident as modulated light,
By selecting the G and B components, output light can be obtained as modulated light of any color.

FIG. 2 is a block diagram showing the configuration of the entire optical system including the optical element. In the figure, 50 is red (R), green (
G), an input light source that emits the three primary colors of red (R) light, and 51 is an optical element according to the present invention.

Further, 52 is a modulation light source, which has the same configuration as the input light source 50, but can now select R, G, and B components. Light emitted from the input light source 50 is guided to the optical fiber 53 and enters the optical element 51 as incident light. On the other hand, the light emitted from the modulating light [52] is guided to the optical fiber 54, enters the optical element 51 as modulated light, and is modulated as described above. and enters the prism 56 for wavelength decomposition,
Here, the light is divided into R, G, and B light and detected by an R phase detector 61, a G detector 62, and a B field detector 63, respectively.

Example 2: This example consists of two optical waveguides that are optically coupled together, and a specific component among the R, G, and B light components is taken out.
This is an example in which an optical element that performs image processing and the like was manufactured.

At low temperatures, the exciton state in the quantum well is stable and undisturbed by thermal vibrations, so the interaction between the quantum well exciton and light increases, and the refractive index of the quantum well becomes more than 10 times that of air. . This is the object of the present invention. The interaction between quantum well excitons, which have a large confinement effect, and light at the liquid helium temperature is exactly the condition for achieving such a huge refractive index.
It can be reduced to a nanometer size, which is less than one-fifth of the wavelength of light in air.

FIG. 3(a) shows the appearance of an optical element according to this embodiment, which has an optical waveguide with a width of nanometer size and performs image processing and the like. The substrate 101 is made of semi-insulating GaAs as in Example 1.
Crystal growth was performed using the wafer under exactly the same conditions as in Example 1. Next, after exposing the resist by electron beam writing, dry etching was performed to form an optical waveguide 102 having a width of 1100n and having two curved portions, and an optical waveguide 103 having a width of 1100n and one curved portion. As shown in FIG. 2(a), the optical waveguides 102 and 103 are close to each other in a part, and the distance between the optical waveguides in that area is 50 nm. Here, the optical waveguide 102 will be referred to as an input optical waveguide, and the optical waveguide 103 will be referred to as an extraction optical waveguide. Further, the reference light 110 is connected to the input optical waveguide 10.
After depositing a 500 nm aluminum film 119, as shown in FIG.
The reference light irradiation window 120 was produced by ion milling.

The operation will be explained below. Input light 107 is input into the input optical waveguide 102 through the spherical fiber 104 . First, consider the case where light that resonates with R-band excitons is input as input light. The input light becomes an R-band polariton and propagates through the optical waveguide. Since the input optical waveguide 102 has a refractive index of 10 or more, the light propagates stably even in an optical waveguide with nanometer radiation. In this case, even if there is a portion where the extraction optical waveguide 103 is close to the extraction optical waveguide 103, the electric field seepage from the input optical waveguide 102 is extremely small.
No transition of polariton to 3 occurs.

Therefore, the output light 108 from the input optical waveguide 102 is emitted, but the output light 108 from the extraction optical waveguide 103 is emitted.
09 is not emitted. However, the coupling region of both optical waveguides,
In other words, the reference light 11 is connected to the input optical waveguide 102 in the approach section.
When R light of the same wavelength as the input light is irradiated with the input light set to 0, the input optical waveguide 102
The electric field seepage from the extraction optical waveguide 1 increases.
A transition of the R-band polariton to 03 occurs.

In this case, output light 109 from the extraction optical waveguide 103 is observed.

Next, an example will be described in which one or more of the above-mentioned optical elements are integrated and used for image processing. First, six of the above optical elements are integrated on one substrate, and each optical element is numbered from 1 to 6 in order from the top. Next, six identical substrates are manufactured, and each substrate is numbered from 1 to ■. The input light 10 is then transmitted through the spherical fiber 104.
7 is input, and output lights 108 and 109 are taken out by the tipped fibers 105 and 106. Further, an optical demultiplexer (not shown) is connected to the fiber that guides the input light 107 and the reference 110, and a monitoring fiber is attached. The monitoring fibers were classified by number for each substrate and each element, and arranged in a matrix. This is shown in FIG. In the figure, each circle corresponds to a light spot from the fiber. As a test pattern, each input light beam 107 is shown in FIG. 4(a).
As shown in the input light pattern, R light is used for optical elements 1 and 2 on all boards, G light is used for optical elements 3 and 4 on all boards, and B light is used for optical elements 5 and 64- on all boards. On the other hand, the test pattern of the reference light is as shown in FIG. 4(b).

R light is used for all optical elements on substrates 1 and 11, G light is used for all optical elements on substrates I [1 and IV, and B light is used for all optical elements on substrates V and VI. At this time, if the pattern of the output light 109 from the extraction optical waveguide 103 is shown as a light spot array from the bulbous fiber 106, it becomes the output light spot array 123 shown in FIG. 4(c).

At this time, polariton transfer from the input optical waveguide 102 to the extraction optical waveguide 103 occurs only when the wavelengths of the input light 107 and the reference light 110 match, so if the input light pattern 121 and the reference light pattern 122 overlap The pattern of the output light spot array 123 can be understood by considering that only the output light 109 is emitted. on the other hand,
The pattern of the output light 10B from the input optical waveguide 102 becomes the output light spot array 124 shown in FIG. 4(d).

Here, the intensity of the output light corresponding to the polariton that has migrated to the extraction optical waveguide 103 decreases, and the intensity of the other output light becomes relatively strong.

In the above explanation, it is assumed that R, G, or B monochromatic light is input to each optical element as a test pattern, but in reality, a mixture of R, G, and B light is input, and the input image is the reference image. The matching part and the remaining part can be extracted. Further, in the above description, the case where six elements are integrated is described, but the number of pixels can be increased by increasing the degree of integration of the elements on the substrate. For example, if we consider the width of I and arrange each element there at an interval of 1 μm, then 10
00 elements can be integrated. If you use 10 boards with 1000 integrated elements, the number of vertical x horizontal pixels will be 100.
Can process 100 images.

Example 3: The third example of the present invention will be explained using FIG. Each quantum well layer is processed into a fine wire shape using electron beam lithography and dry etching to enhance polariton confinement in the lateral direction as well. In the figure, 131 is a substrate;
132 is 19.8 person GaAs quantum well thin wire, 133 is 1
1.3 person Ga As quantum well thin wire, 134 is 8.5
The GaAs quantum well thin wire 135 is a cladding layer.

The width of the thin wire is 40 nm, and the width of the optical waveguide including the cladding is 50 nm. According to this embodiment, the size of the optical element can be further reduced. When the characteristics of a single element were evaluated, results equivalent to those of the element used in Example 2 were obtained.

Embodiment 4: In the optical device described above, the optical waveguide is thin and the incident end is narrow, so the light incident efficiency is only about 10%.

Therefore, in this embodiment, as shown in FIG. 6, a fan-shaped narrowing portion 142 is provided on the end face of the nanometer optical waveguide 141. Here, the width of the end face of the narrowing part is 1μ
m, the length of the narrowing part is 10 μm. According to this embodiment, the incidence efficiency can be increased to 50% or more.

Example 5: A fifth embodiment of the present invention will be described with reference to FIG.

In this embodiment, as shown in FIG. 7, the element is constructed by newly connecting a reference light input optical waveguide 151 to an input optical waveguide 102 in order to input the reference light 110. is the same as in Example 2. Also in this example,
As for the characteristics of a single element, results equivalent to those of the element used in Example 2 were obtained.

Although this embodiment deals with the case where the reference light is incident, the same effect can be obtained with a completely similar configuration also in the case where the modulated light is incident.

(Effects of the Invention) According to the present invention, it is possible to perform parallel optical modulation in a single optical waveguide using the three primary colors of light as basic wavelength components, or to perform image processing using natural colors, and moreover, with high integration. A wavelength multiplexing optical device having characteristics of low input operation can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a wavelength multiplexing optical device that performs optical modulation according to the first embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of the entire optical system including the optical device of the embodiment, and FIG. The figure is an explanatory diagram of a wavelength multiplexing optical device that performs image processing, etc., which is a second embodiment of the present invention, FIG. 4 is an explanatory diagram of image processing by the optical device, and FIG. 5 is a third embodiment of the present invention. FIG. 6 is an explanatory diagram of the fourth embodiment of the present invention, and FIG. 7 is a cross-sectional view of an optical waveguide including a semiconductor thin film layer processed into a quantum wire shape.
It is an explanatory view of an example of. Explanation of symbols 1... Substrate 2... Interferometer optical waveguide 3... Optical waveguide for modulated light incidence 4... Clad layer 5... 19.8 people Ga As quantum well layer 6...
・11.3 people GaAs quantum well layer 7...8.5 people G
aAs quantum well layer 8...Barrier layer 21.22.23...Incoming light 31.32, 33...Outgoing light 41.42, 43...Modulated light 50...Input light source 51...・Optical element 52...
Modulation light source 56...prism 53, 54, 55...
...Optical fibers 61, 62, 63...Detector 101...Substrate 102...Input optical waveguide 103...Output optical waveguide 104, 105, 106...Top fiber 107...
・Input light 108, 109...Output light 110...
・Reference light 131... Board 132-19.8 people G
aAs quantum well wire 133, 11.3-person GaAs quantum well wire 134, 8.5-person GaAs quantum well wire 135, cladding layer 141, nanometer optical waveguide 142, narrowing section 151, ...Reference light input optical waveguide attorney Junnosuke Nakamura (b) Figure 1 RGB (c) (d) Figure 4

Claims (1)

[Claims] 1. Including a plurality of semiconductor thin films each having a different thickness,
The semiconductor thin film has a band gap in the near-infrared region and is sandwiched between barrier materials that have a band gap in the near-ultraviolet region, so that the excited states of electrons and holes formed in the thin film of each layer are It consists of an optical waveguide formed such that the wavelength of the energy level corresponds to a predetermined visible light, and light that resonates with each energy level is input to each layer of the optical waveguide to modulate other light. Wavelength multiplexing characterized in that the phase or refractive index of incident light is changed by irradiating it as light or reference light, and light intensity modulation, color tone modulation, or propagation path switching is performed in any region of visible light. optical element. 2. In the wavelength multiplexing optical device according to claim 1, the optical waveguide includes three layers of semiconductor thin films each having a different thickness,
The optical waveguide is formed so that the wavelengths of the energy levels of the excited states of electrons and holes formed in each of the three thin films correspond to red, green, and blue visible light. wavelength multiplexing optical element. 3. The wavelength multiplexing optical device according to claim 1 or 2, comprising a closed circuit constituted by an optical waveguide. 4. The wavelength multiplexing optical device according to claim 1 or 2, comprising two optical waveguides, the two optical waveguides being close to each other such that electromagnetic coupling occurs between the optical waveguides. A wavelength multiplexing optical device characterized by having a portion. 5. The wavelength multiplexing optical device according to any one of claims 1 to 4, wherein the semiconductor thin film layer is made of a III-V group compound, the barrier is made of a II-VI group compound or a mixed crystal thereof, and A wavelength multiplexing optical device characterized in that a lattice constant mismatch with respect to a semiconductor thin film layer is 0.5% or less. 6. In the wavelength multiplexing optical device according to claim 5, GaAs is used as the III-V group compound forming the semiconductor thin film layer, and ZnS_0_. _1_5Se_0_. A wavelength multiplexing optical device characterized by using _8_5. 7. In the wavelength multiplexing optical device according to any one of claims 1 to 6, the semiconductor thin film layer has a refractive index that is 10 times or more the refractive index of the air, and the width of the optical waveguide is the red color of the air. A wavelength multiplexing optical element characterized in that the wavelength is one-fifth or less of the wavelength of light. 8. In the wavelength multiplexing optical device according to any one of claims 1 to 7, the semiconductor thin film layer is processed into a thin line shape with a width of 40 nm or less in the direction along the substrate surface, and the width of the optical waveguide is 50 nm or less.
A wavelength multiplexing optical device characterized in that the wavelength is reduced to below nm. 9. The wavelength multiplexing optical device according to any one of claims 1 to 8, characterized in that a fan-shaped constriction portion is provided at an end of the optical waveguide. 10. The wavelength multiplexing optical device according to claim 1, further comprising an optical waveguide for irradiating modulated light or reference light. 11. An element consisting of two optical waveguides having portions that are close to each other so that electromagnetic coupling occurs between the optical waveguides according to claim 4, one element corresponding to one pixel,
The original image of natural color is divided into pixels, which are incident on each of the elements, and each element compares the incident pixel with the pixel of the reference image. An image processing method characterized by separating and extracting a common part and a non-common part, arranging the output light of each element two-dimensionally, and outputting images of the common part and the non-common part, respectively.