JPH05281495A - Optical element - Google Patents

Abstract

PURPOSE:To polarize and convert output light by a nonmechanical technique. CONSTITUTION:Gratings 12 are formed at prescribed equal intervals on the surface of an annular waveguide 11 and are so formed that the phase of the gratings 12 and the phase of the progressive waves guided in the waveguide 11 shift by pi per half circumference. A pair of the waveguide 16, 17 are optically coupled to the positions shifted by the half circumference in the circumferential direction of the annular waveguide 12. The light from a laser 12 is selectively applied by an optical switch 15 to these waveguides 16, 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element using a ring-shaped waveguide.

[0002]

2. Description of the Related Art Recently, by miniaturizing various optical elements and integrating them on a substrate using an optical waveguide,
Optical integrated circuits are used that are compact and lightweight, and have stable operating characteristics.

In such an optical integrated circuit, conversion by a grating is used to output the light inside thereof to the outside, and further, in order to convert this output light into linearly polarized light or circularly polarized light, a filter is used. Is generally used.

[0004]

However, in the method using such a filter, it is necessary to mechanically replace various filters in order to convert the output light into linearly polarized light or circularly polarized light. The structure for realizing the work becomes complicated, and the replacement of the filter frequently causes a structural durability problem. Further, since various filters are exchanged mechanically, it takes time to perform the work, and it is difficult to perform a quick polarization conversion. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical element that can rapidly perform polarization conversion of output light by a non-mechanical method.

[0005]

According to the present invention, a grating is formed on the surface at predetermined equal intervals, and the phase of the grating and the phase of a traveling wave guided inside are shifted by π per half circumference. A pair of waveguides that are optically coupled to the ring-shaped waveguide are arranged at positions shifted by approximately half a circumference in the circumferential direction of the waveguide, and light from a light source is selectively applied to these waveguides by a switch means. Is configured to give.

In this case, the ring-shaped waveguide 1 has 2πr / n inside when the radius is r, as shown in FIG.
A traveling wave having a wavelength (where n is an integer) is guided, and the period of the grating 2 is 2πr / m (where m−
By setting n to be an odd number, the emitted light can be extracted outside the surface including the ring.

Now, the period of the grating 2 is 2πr / m
Then, if m = n + 1, then 2π is present on the surface of the waveguide 1.
The grating 2 is formed with a pitch of r / (n + 1). Then, a point A is selected on the waveguide 1, and the points obtained by rotating the point A by π / 2r are set as points B, C, and D, respectively. The phase differences between the guided wave and the grating 2 at points B, C, and D are Δφ (A), Δφ (B), Δφ (C), and Δφ (D), respectively.
Then, when Δφ (A) = 0 at time t = 0, the time changes of Δφ (A), Δφ (B), Δφ (C), and Δφ (D) are as shown in FIG. ..

Here, considering the case where radiated light from the vicinity of points A, B, C, and D is observed on the axis passing through the center O of the waveguide 1, at t = 0. If the emitted light near the point A has the maximum amplitude, the emitted light near the point C also has the maximum amplitude. This is because if the traveling directions of the traveling waves are opposite between points A and C, that is, if the point A is in the + Y direction, it is in the −Y direction at point C, and Δφ (A) and Δφ.
This is because (C) always differs by π. Further, at this time, the radiated light near the point B and near the point D has the smallest amplitude. This is because Δφ (B) and Δφ (D) are Δφ (A) and π, respectively.
This is because they are different by / 2 and -π / 2.

The point at which the emitted light has the maximum amplitude moves with the passage of time. In other words, the point at which the amplitude of the emitted light becomes maximum at t = 0 is point A, but with the passage of time, it moves in the direction of the arrow in the figure, moves sequentially to point B, point C, point D, and again to point A. Come back. As a result, the plane of polarization of the emitted light also rotates, so that if the coupling efficiency of the grating 2 is constant regardless of the angular direction with respect to the center 0, the emitted light can be set to circularly polarized light. The rotation direction of the polarized light can be determined by the direction of the traveling wave in the waveguide 1.

Further, if a traveling wave in the opposite direction is given in the ring-shaped waveguide 1 to guide the standing wave, the emitted light is linearly polarized from the superposition of the standing wave light. be able to. The polarization plane of the linearly polarized light in this case is a constant component of the phases of the traveling waves in opposite directions which are superposed on each other in the waveguide 1, that is, the angular dependence of the two traveling waves is ex.
p (i (ωt-pθ + δ1)) and exp (i (ωt + p)
It can be determined by δ1 and δ2 when θ + δ2)). Here, t is time, θ is the angle shown in FIG. 1, ω,
δ1 and δ2 are constants.

[0011]

As a result, according to the present invention, for the ring-shaped waveguide in which the phase of the grating and the phase of the traveling wave guided inside are shifted by π per half circumference, the waveguide selected by the optical switch is used. Right-handed or left-handed circularly polarized light can be selectively obtained by inputting light from the light source, and standing waves can be guided by inputting traveling waves in opposite directions that are superimposed on each other in the ring-shaped waveguide. As well as wave
By determining the phase of the standing wave corresponding to the phase of the grating, linearly polarized light whose polarization plane is arbitrarily selected can be obtained, and the polarization conversion of the output light can be realized by a non-mechanical method. ..

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 shows a schematic configuration of the same embodiment.
In the figure, 11 is the above-mentioned ring-shaped waveguide, and gratings 12 are formed on the surface of this waveguide 11 at equal intervals.

In this case, the ring-shaped waveguide 11 is provided with light having a wavelength of 2πr / n (where n is an integer), where r is the radius. The gratings 12 on the surface of the waveguide 11 are formed at a pitch of 2πr / (n + 1). As a result, the ring-shaped waveguide 11
Is designed so that the phase of the grating 12 on the surface and the phase of the traveling wave guided in the waveguide 1 are deviated by π per half circumference. On the other hand, 13 is a light source, for example, a laser, and this laser 13 outputs the light having the above-mentioned wavelength of 2πr / n in the ring-shaped waveguide.

An optical switch 15 is connected to the laser 13 via a waveguide 14, and two optical waveguides 16 and 17 are connected to the optical switch 15. The optical switch 15 selects either one of the waveguides 16 and 17 by a switching operation, and the laser 1 is selected for the selected waveguides 16 and 17.
The light given from 3 is given.

A part of each of the waveguides 16 and 17 is close to the ring-shaped waveguide 11, and the proximity points 161 and
At 171 it is optically coupled to the ring-shaped waveguide 11.

However, in such a structure, when the laser 13 outputs light having a wavelength of 2πr / n,
This output is given to the optical switch 15 through the waveguide 14.

Here, the waveguide 16 is formed by the optical switch 15.
Is selected, the output from the laser 13 is given to the waveguide 16 from the optical switch 15, and further to the ring waveguide 11 from the proximity point 161 with the ring waveguide 11 through the waveguide 16. In the ring-shaped waveguide 11, the laser 1 given from the proximity point 161
The output of 3 excites a clockwise traveling wave.

On the other hand, if the waveguide 17 is selected by the optical switch 15, the output from the laser 13 is given to the waveguide 17 by the optical switch 15, and passes through the waveguide 17 to form the ring-shaped waveguide 11. The ring-shaped waveguide 11 is supplied from the proximity point 171. In the ring-shaped waveguide 11, the counterclockwise traveling wave is excited by the output of the laser 13 supplied from the proximity point 171. Become.

As a result, the circularly polarized light output out of the plane from the grating 12 formed on the surface of the ring-shaped waveguide 11 is selected between clockwise and counterclockwise depending on the switching of the waveguides 16 and 17 by the optical switch 15. Will be obtained.

Therefore, in this way, the optical switch 15
The right-handed or left-handed circularly polarized light from the ring-shaped waveguide 11 can be selectively obtained by the switching operation, and the polarization conversion of the output light can be realized by a non-mechanical method. Compared to the need to mechanically replace various filters to perform conversion, it solves all the structural durability problems due to the complicated structure for realizing polarization conversion work and frequent filter replacement. can do. Further, since the time required for switching the circularly polarized light is determined by the response time of the optical switch 15,
Polarization conversion of output light can be performed quickly. Next, FIG. 4 shows a schematic configuration of another embodiment of the present invention. Here, since FIG. 4 has almost the same configuration as that of FIG. 3 described above, the same portions are denoted by the same reference numerals and only different portions will be described.

In this case, the optical switch 15 includes the waveguide 1
It has a function of selecting either one of the waveguides 16 and 17 at the same time while selecting either one of the waveguides 6 and 17 by a switching operation. In addition, a nonlinear optical element 1 made of, for example, LiNbO3 is provided in the middle of each of the waveguides 16 and 17.
8 and 19 are separately provided. The nonlinear optical elements 18 and 19 are capable of arbitrarily controlling the phases of the light guided in the waveguides 16 and 17, respectively.

In such a structure, however, when either one of the waveguides 16 and 17 is selected by the optical switch 15, the ring waveguide 11 is turned clockwise or leftward in the same manner as in the above-described embodiment. It becomes possible to selectively obtain the circularly polarized light around.

Next, the optical switch 15 causes the waveguide 16,
When 17 are selected at the same time, the output from the laser 13 is given from the optical switch 15 to the waveguides 16 and 17, respectively.
1 to the ring-shaped waveguide 1 from the proximity points 161 and 171.
Given to 1. In this case, if a traveling wave of the same intensity is input to the ring-shaped waveguide 11 through the waveguides 16 and 17, the standing wave is guided in the ring-shaped waveguide 11 and the linearly polarized light is output out-of-plane.

From this state, the waveguides 16 and 17 are
The nonlinear optical elements 18 and 19 interposed in the middle of the optical path control the phases of the light guided in the waveguides 16 and 17, respectively, and the grating 12 in the ring-shaped waveguide 11 is controlled.
By determining the phase of the standing wave with respect to the phase of, the plane of polarization of linearly polarized light can be arbitrarily selected.

Therefore, in this way, the optical switch 15
The linear polarization whose polarization plane is arbitrarily selected can be obtained from the ring-shaped waveguide 11 by the switching operation and the polarization conversion of the output light can be realized by a non-mechanical method. Therefore, the same effect as that of the above-described embodiment is expected. You can do it. The present invention is not limited to the above-mentioned embodiments, and can be carried out by appropriately modifying it without departing from the scope of the invention.

[0027]

According to the present invention, since the polarization conversion of the light output out of the plane including the ring-shaped waveguide can be realized by an optical non-mechanical method, the polarization conversion can be performed quickly. In addition, it is possible to solve all the problems of structural complexity and structural durability associated with mechanical structure.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the outline of the present invention.

FIG. 2 is a characteristic diagram showing a temporal change in a phase difference between guided light and a grating used in the description of FIG.

FIG. 3 is a diagram showing a schematic configuration of an embodiment of the present invention.

FIG. 4 is a diagram showing a schematic configuration of another embodiment of the present invention.

[Explanation of symbols]

1, 11 ... Ring waveguide, 2, 12 ... Grating, 13 ... Laser, 14, 16, 17 ... Waveguide, 15 ...
Optical switch, 161, 171, ... Proximity point, 18, 19 ... Non-linear optical element.

Claims (1)

[Claims] 1. A ring-shaped waveguide in which gratings are formed on the surface at predetermined equal intervals so that the phase of the grating and the phase of a traveling wave guided inside are shifted by π per half circumference, and the ring-shaped waveguide. A pair of waveguides that are optically coupled to the ring-shaped waveguide at positions shifted by about half a circumference with respect to the circumferential direction of the waveguide, and a switch means that selectively supplies light from the light source to these waveguides are provided. An optical element characterized by being provided.