JP3078395B2 - Optical element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element which belongs to an optoelectronic technology and is a basic component of an optical integrated circuit.

[0002]

2. Description of the Related Art FIG. 4 is a perspective view showing a typical example of a diffraction grating formed on a waveguide layer. Conventionally, a silicon nitride film is formed on a glass waveguide layer, and the film is patterned and etched to form an uneven surface as shown in FIG. That is, a diffraction grating having a step is formed by producing a patterned mask layer on a silicon nitride layer, eroding a mask opening, and transferring the pattern.

[0003]

It is desirable that the optical integrated circuit is essentially composed of a single mode waveguide, and the structure of the device in the integrated circuit is of the order of wavelength.
Processing requires micrometer-order technology. For example, the thickness of the waveguide layer is about 1 μm, and the width of the waveguide is 4 μm.
It is about 0.5 μm when the diffraction grating period is reached. In order to produce an optical integrated circuit which is an element having such a micrometer structure, an advanced thin film forming technique and a fine pattern processing technique are required.

However, when processing the diffraction grating 7 into irregularities as shown in FIG. 4, processing with the above-described accuracy is necessary. However, satisfactory results cannot be obtained by patterning and etching. Errors have occurred in the emission intensity distribution, the emission focal length, and the like. That is, in manufacturing a diffraction grating or the like, there is an etching step as a main manufacturing procedure that causes an error in the grating shape, and the steps are roughly classified into wet etching performed in an etching solution and dry etching performed in a gas. However, in the wet etching, if the etching progresses anisotropically due to the material or the like, an undercut occurs for the side etching under the mask, and the processing accuracy deteriorates. Therefore, when a processing accuracy of about 1 μm or less is required, a satisfactory result cannot be obtained. In order to overcome such disadvantages of wet etching, dry etching technology has been developed and its isotropy has been improved, but on the other hand, there has been a disadvantage that the sample surface is broken and damaged during processing. .

On the other hand, in the conventional diffraction grating 7, since the shape of the unevenness is determined at the time of fabrication, if it is desired to change the emission angle or the like after fabrication, it is necessary to separately fabricate a diffraction grating of an appropriate shape. Was.

Accordingly, it is an object of the present invention to overcome the above-mentioned drawbacks and to provide a highly accurate optical element.

[0007]

The optical element of the present invention has a substrate, a waveguide layer laminated on the substrate, and a transparent semiconductor layer laminated on the waveguide layer. The semiconductor layer has high-resistance regions and low-resistance regions alternately formed in stripes. Further, an optical element having a means for applying a voltage to a low-resistance region in which a low-resistance region and a high-resistance region are divided into stripes may be used.

[0008]

The optical element in which the high-resistance area and the low-resistance area are formed in stripes in the transparent semiconductor layer produces an accurate emission angle, emission intensity distribution, and the like. Further, by using a material (for example, a piezoelectric material) whose physical property value (refractive index or the like) changes when a voltage is applied, the refractive index can be controlled after the diffraction grating is manufactured.

[0009]

FIG. 1 is a perspective view showing a diffraction grating according to a first embodiment of the present invention. After forming the SiO ₂ buffer layer 2 on the Si substrate 1 by thermal oxidation or sputtering, the Corning 7059 glass waveguide layer 3 is formed. Subsequently, one ZnO layer 4 is formed on the waveguide layer 3 by vapor deposition or sputtering, and then the one ZnO layer 4 is electrically connected to the single ZnO layer 4 by using an ion implantation technique as shown in FIG. The activated high resistance region 4a and low resistance region 4b are formed in stripes. here,
Although the ZnO layer 4 is formed on the waveguide layer 3, the material is a semiconductor material containing a metal oxide as a main component and having transparency in a wavelength region to be used.
This is referred to herein as a transparent semiconductor material. Examples of the transparent semiconductor material include SnO ₂ , ZnO, and ITO (an oxide of indium and tin). That is, the waveguide layer 3
When protons are injected into these materials formed above, the carrier concentration decreases, the resistance increases, and the refractive index decreases. Therefore, proton (H ⁺ ) is added to SnO ₂ , ZnO, ITO, etc.
By directly drawing a pattern such as a diffraction grating on a single transparent semiconductor material with a beam, a refractive index distribution having an arbitrary shape without a step can be formed.

The waveguide layer 3 of the device manufactured as described above
When light is introduced by using a predetermined method, the light reaching the region where the diffraction grating exists is emitted from the waveguide layer 3 to the outside.

Therefore, in this embodiment, by using the ion implantation technique, a manufacturing process such as etching which causes an error in optical characteristics such as an emission angle is eliminated, and a more accurate diffraction grating is realized.

FIG. 2 is a front view showing a diffraction grating according to a second embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals. An SiO ₂ buffer layer 2, a waveguide layer 3 and a ZnO layer 4 are sequentially stacked on a Si substrate 1,
By injecting protons into the O layer 4, the high resistance region 4
a and the low resistance region 4b are formed in a stripe shape. The electrode terminals 5 are connected to the low resistance regions 4b at positions opposing each other alternately so that a voltage can be applied between the adjacent low resistance regions 4b.

Here, since the ZnO layer is made of a piezoelectric material, when a voltage is applied to the electrode terminal 5, a potential difference is generated between the adjacent low-resistance regions 4b. Causes distortion. This distortion also distorts the waveguide layer 3 existing below the high-resistance region 4a, so that a refractive index distribution different from that when no distortion exists can be realized. That is, the amount of distortion is adjusted by changing the applied voltage, and the emission angle and emission intensity distribution of the guided light are controlled.

Therefore, in this embodiment, a material whose physical property value (refractive index or the like) changes by application of a voltage is used, and the refractive index is controlled after the diffraction grating is manufactured, so that the stripe shape of one form can be reduced to one.
This is realized by two diffraction gratings, and an arbitrary refractive index distribution can be obtained.

FIG. 3 is a side view showing a third embodiment of the present invention. In this embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals. By laminating the substrate 1 and the waveguide layer 3 in order, and further injecting protons into the ZnO layer 4 which is a transparent semiconductor material laminated on the waveguide layer 3, the high resistance region 4a and the low resistance region 4b are striped. The optical element formed above is used for an optical switch. That is, the photodetector 6 is arranged in a direction in which the introduced light passes through the waveguide layer 3 and exits therefrom. Although not shown in this optical element, the low resistance divided into stripes as in the second embodiment. It has an electrode terminal for applying a voltage between the regions 4b.

Here, when a voltage is applied to the low resistance region 4b, the high resistance region 4a (the region where the electrostriction effect is remarkable) is distorted, and the distortion changes the absorption edge in the region immediately below the high resistance region 4a. Can be. If a voltage is applied so that the absorption edge is smaller than the energy of the waveguide light, the guided light is absorbed immediately below the high-resistance region 4a, and the guided light cannot be detected.

Therefore, in the optical switch according to the present embodiment,
Since the absorption end of the waveguide layer 3 is changed, the efficiency and speed of absorption are increased, and all light can be absorbed in a short distance.
The device can be downsized. Further, since the intensity of the detected light can be modulated by continuously changing the applied voltage, it can be used as an optical modulator.

In these examples, the high-resistance layer is formed only by ion implantation, but the same result can be obtained by performing an appropriate heat treatment after the implantation. Further, the present invention is not limited to only the diffraction grating, other waveguide type optical elements such as a beam splitter and a micro Fresnel lens,
Also available.

[0019]

As described above, the present invention makes it possible to accurately form a linear diffraction grating by using an ion beam (H ⁺ ) and obtain an accurate emission angle, emission intensity distribution and the like.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention.

FIG. 2 is a front view showing a second embodiment of the present invention.

FIG. 3 is a side view showing a third embodiment of the present invention.

FIG. 4 is a perspective view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Buffer layer 3 Waveguide layer 4 ZnO layer 4a High resistance area 4b Low resistance area 5 Electrode terminal 6 Photodetector 7 Diffraction grating

Claims (2)

(57) [Claims] 1. A semiconductor device comprising: a substrate; a waveguide layer laminated on the substrate; and a transparent semiconductor layer laminated on the waveguide layer. An optical element having a resistance region and a low resistance region alternately. 2. An optical element according to claim 1, further comprising means for applying a voltage to a low-resistance region in which a low-resistance region and a high-resistance region are divided into stripes.