JPS6218518A - Optical modulation element - Google Patents

Abstract

PURPOSE:To enable an optical modulator without polarization dependency and the constitution of an optical switch by installing plural interdigital electrode pieces having wide and narrow gaps on a light guide formed on a photoelectrical substrate, impressing a voltage between respective electrodes and making a section changing the phase of light longer. CONSTITUTION:The interdigital electrode piece 53 installed on the 1st electrode 51 and the interdigital electrode piece 54 installed on the 2nd electrode 52 are alternately disposed in such a way that the interdigital electrode piece 53 and the interdigital electrode piece 54 positioned at both sides of said piece 53, or said piece 54 and the interdigital electrode piece 53 positioned at both sides of said piece 54 can face each other by passing the one through a narrow clearance 55 and the other through a wide clearance 56. Thus the interdigital electrode piece 53 installed on the 1st electrode 51 and the interdigital electrode piece 54 installed on the 2nd electrode 52 are alternately disposed, thereby making the section changing the phase of light longer.

Description

[Detailed Description of the Invention] [Summary] A comb-shaped electrode piece having two types of wide and narrow gaps is provided on an optical waveguide formed on a substrate made of electro-optic crystal (hereinafter referred to as an electro-optic substrate), The present invention realizes an optical modulation element that enables the construction of optical modulators and optical switches without polarization dependence.

[Industrial application field]

The present invention relates to an optical device constituting an optical communication system,
In particular, the present invention relates to a waveguide-type optical modulation element comprising an optical waveguide formed on an electro-optic substrate and an electrode formed on the optical waveguide.

With the spread of optical communication technology, there has been an increasing demand for improved reliability, smaller size, and lower prices for the optical devices that make up optical communication systems. Development of optical devices is desired.

For example, an optical modulation element consisting of an optical waveguide formed by diffusing titanium (Ti) or the like on an electro-optic substrate such as lithium niobate (LiNb03) and an electrode provided on the optical waveguide is a small-sized optical modulator. The drive voltage is low, high-speed operation is possible, and it can be built up.

That is, optical modulators and optical switches that include such optical modulation elements in optical circuits can be made smaller and lower in price, and are suitable for mass production, and are expected to have even higher reliability.

[Conventional technology]

FIG. 3 is a plan view showing an example of a Matsuhatsu Ender interferometer type optical modulator, and FIG. 4 is a plan view showing a conventional optical modulation element.

In Fig. 3, the Matsuhatsu Ender interferometer type optical modulator is
It is composed of an electro-optic substrate 1, an optical waveguide 2 formed on the electro-optic substrate 1, and an optical modulation element 3. Optical waveguide 2
consists of an input optical path 21, a reference optical path 22, a modulated optical path 23, and an output optical path 24, and a light modulation element 3 is formed in the middle of the modulated optical path 23.

The light entering the input optical path 21 is divided into two, and the phase of the light guided through the modulated optical path 23 is controlled by the optical modulation element 3.

On the other hand, the light guided through the reference optical path 22 is guided without having its phase controlled. These two lights are combined into intensity-modulated light, which is output from the output optical path 24.

Further, as shown in FIG. 4(a), the light modulation element 3 includes an optical waveguide 23 formed on an electro-optic substrate l, and an insulating material (A1203 or S i 02) formed on the optical waveguide 23.
), and a pair of electrodes 26 and 27 formed on the buffer R25.

By applying a voltage between the electrodes 26 and 27, the refractive index of the optical waveguide 23 changes by Δn, and the optical path length changes by Δn.
Since the phase changes by n-L, the phase of the guided light changes. That is, the direction in which the phase changes changes depending on the polarity of the electrodes 26 and 27, and the magnitude of the phase change can be controlled by the magnitude of the voltage.

[Problem that the invention seeks to solve]

However, when a uniaxial crystal such as LiNbO3 is used as a substrate, in order to effectively utilize the electro-optic effect, it is necessary to apply an electric field in the direction of the optical axis of the crystal, that is, in the direction perpendicular to the plane of the paper in Figure 4 (al. However, in the case of the optical modulation element 3 shown in FIG. The problem was that they were different.

This problem can be solved by aligning the propagation direction of the waveguide and the direction of the electric field with the optical axis direction as shown in Fig. 4 (bl), but in this case, the electrode gap g and the refractive index change Δn are The optical path length changes only by the product Δn・g, and sufficient phase modulation cannot be obtained.Here, Δn and 1/g
For example, even if the gap g is increased, the effect of strengthening the phase modulation cannot be obtained.

[Means for solving problems]

FIG. 1 is a plan view showing one embodiment of a light modulation element according to the present invention.

The above problem is solved by the optical waveguide 41 formed on the electro-optic substrate 1 shown in FIG. The provided comb-like electrode pieces 53 and the comb-like electrode pieces '54 provided on the second electrode 52 are alternately arranged, and the comb-like electrode pieces 53 and the comb-like electrode pieces 54 located on both sides thereof are arranged alternately. , or the comb-shaped electrode piece 54 and the comb-shaped electrode piece 53 located on both sides thereof.
These problems can be solved by the optical modulation element of the present invention, which is arranged such that one side faces each other with a narrow gap 55 in between and the other side faces with a wide gap 56 in between.

[Effect]

A plurality of comb-like electrode pieces having two types of wide and narrow gaps are provided on an optical waveguide formed on an electro-optic substrate, and a voltage is applied between each electrode to lengthen the section in which the phase of light is changed. Accordingly, it is possible to realize an optical modulation element that enables the construction of an optical modulator or an optical switch without polarization dependence.

[Examples] Examples of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 2 is a side sectional view of the optical modulation element according to the present invention.

In FIGS. 1 and 2, the comb-shaped electrode pieces 53 provided on the first electrode 51 and the comb-shaped electrode pieces 54 provided on the second electrode 52 are arranged alternately, so that the light The period in which the phase of the phase is changed can be made longer.

A comb-shaped electrode piece 53 and comb-shaped electrode pieces 5 located on both sides thereof
A voltage is simultaneously applied between the electrode pieces 53 and 4, and a force that changes the phase of the light in opposite directions acts. Since the electric field does not penetrate into the vertical direction of the substrate and the buffer layer 42 is present, the power to change the phase of light is weak.
The electric field due to the voltage applied between 3 and the electrode piece 54 is
Since the light reaches the optical waveguide 41 sufficiently, the power to change the phase of the light is strong.

Therefore, the change in the phase of the light due to the voltage applied between the electrode pieces 53 and 54 that face each other with a wide gap 56 in between, is It is not canceled by the effect of the voltage applied between them.

Such an optical modulation element has no polarization dependence and can perform equivalent phase modulation on light polarized in any direction guided through an optical waveguide. Therefore, for example, by providing the light modulation element of the present invention in the optical circuit as the light modulation element of the Matsuhatsu Ender interferometer type optical modulator shown in FIG. 3, it is possible to realize an optical modulator without polarization dependence. can.

Furthermore, an optical switch without polarization dependence is constructed by providing a two-manpower, two-output 3db coupler that couples polarized light beams in arbitrary directions one-to-one at the input/output section of the Matsuhatsu Ender interferometer type optical modulator. It is also possible to do so.

That is, by providing the optical modulation element of the present invention in an optical circuit, it is possible to realize miniaturization and cost reduction of an optical modulator or optical switch, and to further improve reliability.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide an optical modulation element that realizes miniaturization and cost reduction of optical modulators and optical switches, and further improves reliability.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing an embodiment of the optical modulation element according to the present invention, Fig. 2 is a side sectional view showing an embodiment of the optical modulation element according to the invention, and Fig. 3 is a Matsuhatsu Ender interferometer type. FIG. 4 is a plan view showing an example of an optical modulator. FIG. 4 is a plan view showing a conventional optical modulation element. In the figure, l is an electro-optical substrate, 41 is an optical waveguide, 42 is a buffer layer, 51 is a first electrode, 52 is a second electrode, 53.54 is a comb-shaped electrode piece, 55.56 is a gap between electrodes, respectively. /1-The first drawing of the picture shown by Hatsukushi Kazuoka Bata, Figure 1, 9e 珂・W-゛)e The old temple and threat・l >'f
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Claims (1)

[Claims] An optical waveguide (41) formed on an electro-optic substrate (1), and a first electrode (51) formed on the optical waveguide (41).
and a second electrode (52), and a comb-shaped electrode piece (53) provided on the first electrode (51).
and a comb-shaped electrode piece (54) provided on the second electrode (52).
), and the comb-shaped electrode piece (53) and the comb-shaped electrode piece (54) located on both sides thereof, or the comb-shaped electrode piece (54) and the comb-shaped electrode piece (54) located on both sides thereof. A light modulation element characterized in that tooth-shaped electrode pieces (53) are arranged so that one side faces each other with a narrow gap (55) interposed therebetween and the other side faces each other with a wide gap (56) interposed therebetween.