KR0152709B1 - Optical attenuator based on quarter wave plates - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light intensity controller using a laminated mirror having a thickness of one quarter of the wavelength of transmitted light. The present invention is characterized in that the light intensity controller is transparent and different for a given wavelength in an information processing apparatus using light. The two layers of refractive index are placed in front of the photowindow in front of the photowindow by arranging alternating structures in the material by the thickness of which the light changes phase by 90 degrees, that is, the distance the light advances by a quarter of a wavelength. The present invention is characterized by adjusting the light intensity incident to each light window by changing the number of, the first of the present invention is well known the physical properties of the laminated mirror and the stacking technique is also common, so that exactly the desired transmittance ( transmittance), and secondly, the sum of transmittance and reflectance of this laminated mirror is always constant. Transmittance can be measured non-destructively by measuring the reflectance at any time even after the device is completed. Third, since a part of the information light is reflected, it is possible to add composition by using it. The effect is that the overall heat generation can be reduced compared to the case of using.

Description

Optical attenuator based on quarter wave plates

1 is a cross-sectional view in which a light attenuator made of a laminated mirror is installed in each light window according to the present invention.

2 is a graph showing the transmittance according to the number of layers (thickness) of the laminated mirror having an AlAs / Al _0.7 Ga _0.3 As structure at a wavelength of 850 nm.

3 is a diagram showing the transmittance according to the number of layers (thickness) of a laminated mirror having an AlAs / Al _0.5 Ga _0.5 As structure at a wavelength of 850 nm.

4 is a graph showing the transmittance according to the number of layers (thickness) of the laminated mirror having an AlAs / Al _0.3 Ga _0.7 As structure at a wavelength of 850 nm.

5 is a diagram showing the transmittance according to the number of layers (thickness) of the laminated mirror having an AlAs / Al _0.1 Ga _0.9 As structure at a wavelength of 850 nm.

6 is a graph showing the transmittance according to the thickness when GaAs is used as the absorbing layer at a wavelength of 850 nm.

The present invention relates to a light intensity controller using a laminated mirror, and more particularly, to a light intensity controller using a laminated mirror having a thickness of one quarter of the wavelength of transmitted light.

In general, information processing technology using electrons based on highly integrated silicon circuits has continued to grow remarkably, and its density is expected to continue to improve for the time being.

However, on the other hand, information processing technology using light has been continuously discussed to overcome the foreseeable limitations of the technology using electronics, and some have reached the practical stage.

The biggest advantage of optical technology is the large amount of highly integrated parallel processing of information, and several optical logic schemes have already been proposed.

In other words, a number of optical logic elements are arranged in two dimensions, each receiving and processing information in the form of optical signals.

For this purpose, however, it is necessary to appropriately adjust the light intensity entering the optical window of each optical logic element (Reference literature: AL Lentine, DAB Miller, JE Henry, JE Cunningham, LMF Chirovsky, and LA D'Asaro, Optical). logic using electrically connected quantum well PIN diode modulators and detectors, Applied Physics Vol. 29, No. 14, pp. 2153-2163 (1990)).

Such a structure is usually grown through epitaxy of a group III-V compound semiconductor using molecular beam epitaxy (MBE), metalorganic chemical vapor epitaxy (MOCVD), and the like, which have recently been rapidly developed.

In this case, the composition using the light absorber which adjusts the light intensity passing by stacking the material which absorbs the light of the wavelength used for light intensity control by adjusting the thickness is proposed.

The proposed composition for attenuation of the light intensity of each light window in the conventional light information processing structure is to install a light absorber of a suitable thickness in each light window.

First, however, in reality, the thickness of the absorber is determined by two stages of growth and etching, where it is almost impossible to investigate the thickness nondestructively, and it is very difficult to investigate the thickness of a specific light window even by using a destructive method. There was a problem.

Second, even when the thickness of the light absorber is known, the attenuation of the light intensity is calculated through calculation and is not directly measured.

Third, there is a problem that causes the problem of heat generation because it absorbs light and changes it into heat.

Although the composition using the light absorber has been proposed, there are also problems such as difficulty in measuring the transmittance in actual application.

In this case, each of the micrometer-sized optical windows arranged in this dimension enters a lot of independent light. In some cases, the light intensity that enters specific light windows enters other light windows. It needs to be reduced in proportion to the light intensity.

The present invention solves the problems of attenuator composition using an absorbing layer by using a composition installed on each light window at a thickness suitable for stacking mirrors that alternately stack two materials having different refractive indices and having different refractive indices. I want to relax or eliminate.

Therefore, in order to solve the above problems, the present invention provides two materials having a different refractive index and transparent to a given wavelength in an information processing apparatus using light, each of which has a 90 degree phase change in light, that is, light Light intensity regulator using laminated mirrors that adjust the intensity of light incident on the light window by arranging alternately stacked structures in front of the light windows by varying the distance of one wavelength advance by changing the number of layers of each structure. The purpose is to provide.

A feature of the present invention for achieving the above object is a light intensity controller, in the information processing apparatus using light, two materials having a different refractive index and transparent to a given wavelength, each of which shows a phase change of 90 degrees in the material By adjusting the thickness, that is, by arranging alternating structures in front of the light windows by the distance that the light advances by one quarter, changing the number of layers of each light window, it is possible to adjust the light intensity incident to each light window. It is to feature.

Conventionally, the light intensity is adjusted using a light absorber, but in the present invention, the light intensity is controlled by using a laminated mirror structure in which no light absorption occurs.

That is, the present invention proposes a composition in which a heterogeneous laminated structure is used as a light attenuation attenuator instead of an absorber.

It proposes a composition to install so-called laminated mirrors in each light window, which absorbs no light at all, and so-called stacked mirrors, in which two materials having different refractive indices are alternately stacked in a quarter wavelength thickness.

In other words, the laminated mirror, which has been used for the purpose of reflecting light, is used as a light attenuator for transmission.

An efficient adjustment of the light intensity incident on each of the light windows of several micrometers required for a large amount of parallel optical information processing apparatus will be described.

Hereinafter, with reference to the accompanying drawings will be described in detail one of the preferred embodiments according to the present invention.

1 is a cross-sectional view in which a light attenuator made of a laminated mirror is installed in each light window according to the present invention.

Referring to Fig. 1, a cross-sectional view of a light attenuator made of a laminated mirror according to the present invention will be described as follows.

Here, each light intensity is adjusted as intended by passing through laminated mirror structures that give an appropriate transmittance for each light window before the light carrying the information reaches the light window of the optical device.

This laminated mirror is a structure in which two materials having a different refractive index and transparent for a given wavelength are alternately stacked in the material by a thickness of 90 degrees, that is, a distance in which the light advances one quarter of a wavelength.

It can be uniformly stacked on the entire area using epitaxy equipment such as MBE or MOCVD, and then wetted by acid for each window, or the desired thickness using well-established etching methods such as RIE. Only leave

In order to explain the role of the stacked mirror structure, it is assumed that an optical signal having a wavelength of 850 nm is used.

In this wavelength band, a laminated mirror structure of AlAs / Al _x Ga _lx As is appropriate.

(1) alternates two materials that are transparent for a given wavelength and have different refractive indices, each one by the thickness of which the light has a phase shift of 90 degrees within it, that is, the distance the light advances one quarter of the wavelength. Stacked structure, the basic unit of laminated mirrors.

In (2), the laminated mirror is completely removed.

In parts (3), the desired transmittance is obtained by partially removing the laminated mirror to reduce the number of layers.

(4) is an optical signal directed to each light window.

Denoted at 5 is an optical signal receiver through each optical window.

(6) are laminated mirror structures which give an appropriate transmittance for each light window.

2 to 5 show the transmittance according to the calculated mirror thickness by varying the x value of this structure from 0.2 to 0.7, respectively, at intervals of 0.2. The principles and methods on which this calculation is based are explained in the following references.

H. A. Macleod, Thin-film Optical Filters, 2nd ed., Adam Hilger Ltd, Bristol, 1986.

These materials do not absorb light at any given wavelength, so the reflectance is the subtraction of the transmission in each case.

2 is a diagram showing the transmittance according to the number of layers (thickness) of the laminated mirror having the AlAs / Al _0.7 Ga _0.3 As structure at a wavelength of 850 nm.

Referring to FIG. 2, the transmittance according to the number of layers (thickness) of the laminated mirror having the AlAs / Al _0.7 Ga _0.3 As structure at a wavelength of 850 nm is described as follows.

In the case of x = 0.7, the transmittance when the stack is about 12 pairs is almost close to 1, and it can be seen that the transmittance gradually decreases as the number of stacks decreases or increases.

In this case, both materials forming the stack have a relatively large energy gap.

3 is a graph showing the transmittance according to the number of layers (thickness) of the laminated mirror having the AlAs / Al _0.5 Ga _0.5 As structure at a wavelength of 850 nm.

Referring to FIG. 3, the transmittance according to the number of layers (thickness) of the laminated mirror having the AlAs / Al _0.5 Ga _0.5 As structure at a wavelength of 850 nm is described as follows.

In the case of x = 0.5, the transmittance when the stack is about 7 pairs is almost 1, and it can be seen that the transmittance gradually decreases as the number of stacks decreases or increases.

In this case, both materials forming the stack are smaller than when the energy gap is x = 0.7.

4 is a graph showing the transmittance according to the number of layers (thickness) of the laminated mirror having an AlAs / Al _0.3 Ga _0.7 As structure at a wavelength of 850 nm.

Referring to FIG. 4, the transmittance according to the number of layers (thickness) of the laminated mirror having the AlAs / Al _0.3 Ga _0.7 As structure at a wavelength of 850 nm is described as follows.

In the case of x = 0.3, when the stack is about 5 pairs, the transmittance is almost 1, and it can be seen that the transmittance gradually decreases as the number of stacks decreases or increases.

In this case both layers of the stack are smaller than when the energy gap is x = 0.5.

FIG. 5 is a graph showing the transmittance according to the number of layers (thickness) of the laminated mirror having the AlAs / Al _0.1 Ga _0.5 As structure at a wavelength of 850 nm.

Referring to FIG. 5, the transmittance according to the number of layers (thickness) of the laminated mirror having the AlAs / Al _0.1 Ga _0.9 As structure at a wavelength of 850 nm is described as follows.

In the case of x = 0.1, the transmittance when the stack is about 4 pairs is almost 1, and it can be seen that the transmittance gradually decreases as the number of stacks decreases or increases.

In this case, both materials forming the stack are smaller than when the energy gap is x = 0.3.

6 is a diagram showing the transmittance according to the thickness when using GaAs as an absorbing layer at a wavelength of 850 nm.

Referring to FIG. 6, the transmittance according to thickness when GaAs is used as an absorbing layer at a wavelength of 850 nm is described as follows.

This is another change in the absorption layer thickness of the transmittance when the absorption layer is formed by using a material having an absorption coefficient of 17000 / cm.

When the light intensity attenuation ratios of the two light windows are specifically determined, it can be seen that the difference in thickness between the respective absorbing layers is almost the same when comparing FIG. 5 and FIG.

Application fields of the present invention include massive parallel processing as an advantage of information processing using light.

Therefore, in the present invention as described above, first, the physical properties of the laminated mirror are well known, and the technique of stacking them is widely used, and thus, the desired transmittance can be accurately obtained. Second, the transmittance and reflectance of the laminated mirror are obtained. Since the sum is always constant, the transmittance can be measured non-destructively by measuring the reflectance at any time after the device is completed. Third, since a part of the information light is reflected, the composition using this can be added. Since it does not absorb light, the effect is that the overall heat generation can be reduced compared to the case of using an absorber.

Claims (1)

In the light intensity controller, two materials having a different refractive index and transparent to a given wavelength in an information processing device using light, each having a thickness of 90 degree phase change in the material, that is, the light advances a quarter wavelength A light intensity controller using a laminated mirror, characterized in that by arranging the structure alternately stacked by the distance in front of the light window to change the number of layers of this structure for each light window to adjust the light intensity incident to each light window.