JPH0990437A - Waveguide input/output device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waveguide input/output device with which working of gratings is easy and design, etc., are simple. SOLUTION: The gratings 3 are formed in a thin-film waveguide 2 disposed on a glass substrate 1 and a refractive index gradient film 4 is formed to cover these gratings 3. The refractive index of this refractive index gradient film 4 is increased gradually in the progression direction of guided light L1 . Materials which are changed in the refractive index when voltage is impressed thereon, more specifically, ZnO, PLZT, LiNbO3 , etc., are used as the material of, for example, the refractive index graded film 4 in order to grade the refractive index of the refractive index graded film 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveguide input / output device, and more particularly to an optical switch and an optical modulator of an optical computer, an optical switch and an optical demultiplexer and an optical modulator of optical communication, a laser beam printer / copier. The present invention relates to a waveguide input / output device such as an optical deflector such as a scanner or an optical modulator.

[0002]

2. Description of the Related Art In a conventional waveguide input / output device, a chirp grating has been proposed as a means for condensing light traveling in a thin film waveguide at one point outside the device. The chirped grating utilizes the property that the refractive index increases as the pitch of the grating decreases, and is a grating provided on the substrate with the pitch changed.

[0003]

However, this chirped grating requires precise processing, the line width of the portion with a small pitch requires a processing technique of the order of submicron, and there is a problem that the design etc. is complicated. It was Therefore, an object of the present invention is to provide a waveguide input / output device that is easy to perform grating processing and has a simple design and the like.

[0004]

In order to achieve the above object, a waveguide input / output device according to the present invention comprises: (a) a thin film waveguide provided on a substrate; and (b) a waveguide provided on the waveguide. It is characterized by comprising a provided grating and (c) a refractive index gradient film covering the grating.
Here, the refractive index gradient film is a film having a different refractive index in the traveling direction of light (hereinafter, referred to as guided light) traveling in the thin film waveguide.

[0005]

With the above structure, since the refractive index of the refractive index gradient film changes in the traveling direction of the guided light, the refractive index of the guided light emitted to the outside differs depending on the emission position from the waveguide. At the same time that the guided light is emitted, it is also condensed.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a waveguide input / output device according to the present invention will be described below with reference to the accompanying drawings.
In each embodiment, the same components and the same portions are denoted by the same reference numerals. [First Embodiment, FIGS. 1 and 2] The waveguide input / output device of the first embodiment is provided with a gradient index film that utilizes the electro-optic effect. As shown in FIG. 1 and FIG. 2, the waveguide input / output device generally includes a substrate 1, a thin film waveguide 2 formed on the substrate 1, an incident grating (not shown), and an emitting grating 3. And the refractive index gradient film 4
And a pair of electrodes 5a and 5b and a DC power supply 6.

As the substrate 1, for example, a glass substrate is used. The thin film waveguide 2 is made of, for example, ZnO or P.
A piezoelectric material such as LZT or LiNbO ₃ is used, and laser ablation method, sputtering method,
It is formed by means such as a CVD method. The entrance and exit gratings 3 are provided on the thin-film waveguide 2 at a constant pitch, and the same material as the thin-film waveguide 2 is used as the material thereof. These gratings 3 are formed by a photolithography method using an electron beam drawing apparatus, a selective sputtering method using a lift-off method, a CVD method,
Alternatively, it is formed by a method such as an etching method.

The gradient refractive index film 4 is formed on the thin film waveguide 2 so as to cover the emitting grating 3 and is made of a material having an electro-optical effect, such as ZnO, PLZT or LiNbO _3. It This gradient refractive index film 4 is formed by means of a sputtering method, a CVD method, a sol-gel method, or the like. The pair of electrodes 5a and 5b are formed on both sides of the refractive index gradient film 4. A resistor material is used for one electrode 5a so that a potential difference is generated between both ends,
A material having good conductivity such as aluminum is used for the other electrode 5b. Then, the DC power source 6 is provided on both ends of the electrode 5a.
When a voltage is applied by the electrode 5b and the electrode 5b is grounded, a voltage is applied between the electrodes 5a and 5b, that is, the gradient index film 4
An electric field having a voltage distribution inclined with respect to the traveling direction of the guided light L ₁ is generated therein. As a result, the refractive index gradient film 4 gradually increases in refractive index in the traveling direction of the guided light L ₁ due to the electro-optical effect.

Next, a waveguide input / output device having the above structure
The function and effect of the device will be described. Waveguide traveling through the thin film waveguide 2
Light L₁Output to the outside of the device through the output grating 3.
Is shot. At this time, the emitted light L₂In the gradient index film 4
Although it progresses, the refractive index of the refractive index gradient film 4 depends on how the guided light travels.
As it gradually increases in size,
The light is emitted from the waveguide 2 at a position on the left side of the grating 3.
Emitted light L ₂Has a small refractive index, and the waveguide
Outgoing light L emitted from 2₂Has a large refractive index. Follow
Output light L₂Will be collected. That is,
The gradient of the refractive index of the folding rate gradient film 4 causes
The chirp grating structure by changing the pitch of ring 3
It is possible to obtain the same effect as when it is made. This refraction
The slope of the rate changes the voltage applied by the DC power supply 6.
The voltage of the DC power supply 6 is changed because it changes depending on
Therefore, the emitted light L₂The condensing position of can be changed
(L in the figure₂'reference).

When the refractive index of the substrate 1 is n _s , the refractive index of the thin film waveguide 2 is n _f , and the refractive index of the gradient index film 4 is n _c , the relational expression n _s <n _c <n _f If the respective materials are selected so as to satisfy the requirements, the pitch of the grating 3 can be increased, and the grating processing becomes easier.

[Second Embodiment, FIGS. 3 and 4] The waveguide input / output device of the second embodiment is provided with a gradient index film utilizing the thermo-optic effect. As shown in FIGS. 3 and 4, the gradient index film 14 is formed so as to cover the emitting grating 3, and a material having a thermo-optical effect, for example, SnO ₂ is used as the material thereof. SnO ₂ generates heat when a current is applied to it, and its refractive index changes with temperature. The refractive index gradient film 14 is formed by a method such as a sputtering method or a vapor deposition method.

On the right side of the refractive index gradient film 14, a pair of electrodes 15a and 15b are arranged with the refractive index gradient film 14 interposed therebetween. When a voltage is applied to the electrodes 15a and 15b by the DC power supply 16, a current flows to the right side of the refractive index gradient film 14 to generate heat in this portion, and the refractive index increases due to the thermo-optic effect. That is, the refractive index of the refractive index gradient film 14 gradually increases in the traveling direction of the guided light L ₁ . Therefore,
The emitted light L ₂ will be condensed.

[Third Embodiment, FIG. 5] The waveguide input / output device of the third embodiment is provided with a refractive index gradient film whose refractive index is changed by ion implantation or proton exchange.
As shown in FIG. 5, the refractive index gradient film 24 is processed so that the number of implanted ions and the number of exchanged protons gradually increase in the traveling direction of the guided light L ₁ . Ions and protons are driven into the gradient index film 24 by an ion gun and a proton gun, respectively. Since the refractive index increases as the number of injected ions or the number of exchanged protons increases, the refractive index of the refractive index gradient film 24 is the guided light L.
It gradually increases in the direction of travel of ₁ . Therefore, the emitted light L ₂ is condensed. LiNbO ₃ or the like is used as the material of the gradient index film 24.

[Other Embodiments] The waveguide input / output device according to the present invention is not limited to the above embodiment.
Various modifications can be made within the scope of the gist. The refractive index gradient film does not necessarily have to have a gradient in the refractive index in the traveling direction of the guided light, and may have a different refractive index in a stepwise or discontinuous manner.

Further, an antireflection film may be further formed on the surface of the gradient index film to improve the incidence efficiency and the emission efficiency. This antireflection film is for preventing the emitted light from being reflected at the interface between the refractive index gradient film and air when the emitted light is emitted from the refractive index gradient film to the outside of the device. further,
In the above-described embodiment, only the case of the emitting grating has been described, but the incident grating can also be covered with the gradient index film. In this case, diffused light emitted from the light source or the like can be efficiently incident on the thin film waveguide.

[0016]

As is apparent from the above description, according to the present invention, since the refractive index gradient film is provided on the grating, the incident grating can be changed from the light source etc. without changing the pitch of the grating. The emitted diffused light can be efficiently incident on the thin film waveguide, and the emission grating can also collect the guided light at the same time.

Further, by controlling the gradient of the refractive index of the gradient index film, it is possible to easily control the focusing position and correct the pitch of the grating.

[Brief description of drawings]

FIG. 1 is a partial plan view showing a first embodiment of a waveguide input / output device according to the present invention.

FIG. 2 is a cross-sectional view showing the operation of the waveguide input / output device shown in FIG.

FIG. 3 is a partial plan view showing a second embodiment of a waveguide input / output device according to the present invention.

FIG. 4 is a sectional view showing the operation of the waveguide input / output device shown in FIG.

FIG. 5 is a sectional view showing a third embodiment of the waveguide input / output device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Thin film waveguide 3 ... Grating 4, 14, 24 ... Gradient index film

Claims (1)

[Claims] 1. A waveguide entrance, comprising: a thin film waveguide provided on a substrate; a grating provided on the waveguide; and a refractive index gradient film covering the grating. Output device.