JPH1090636A - Optical semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To freely set a polarization rotation angle of a semiconductor waveguid type polarization rotating element in some range by the injecting current to a heater by arranging the heater capable of raising temps. of waveguides by a turning on electricity in the vicinity of the whole on one part of the waveguides. SOLUTION: This polarization rotating element is a semiconductor waveguide type polarization rotating element which is formed on a semiconductor substrate 12 and in which a waveguide segment 6 whose sectional structure or path is asymmetric with respect an axis vertical to the progressing direction of a light beam and a waveguide segment 7 having a structure in which the left and the right of the segment are reversed with respect to the axis vertical to the progressing direction of the light beam are cascaded in cycles of one or more. Moreover, a heater 8 capable of raising the temps. of waveguides by the turning on electricity is provided in the vicinity of the waveguide segments 6, 7 of this element and the difference δ between propagation constants of the waveguides and a coupling constant (k) can be changed by raising temps. of the waveguides with the energizing amount to the heater 8 and, thus, the polarization rotation angle is set to an angle different from that of before the turning on electricity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor waveguide polarization rotator.

[0002]

2. Description of the Related Art Semiconductor waveguide optical amplifiers and semiconductor waveguide optical modulators are widely used as useful light control elements. However, semiconductors have anisotropy due to their crystal structure, and the performance of these elements also differs depending on the polarization direction of an incident optical signal. Since the polarization plane of the optical signal rotates irregularly during the transmission of the optical fiber, the polarization plane of the optical signal transmitted through the optical fiber must be changed when using a semiconductor waveguide optical amplifier or a semiconductor waveguide optical modulator. It is necessary to match a polarization plane suitable for a semiconductor waveguide optical amplifier or a semiconductor waveguide optical modulator. The semiconductor waveguide polarization rotator can rotate the plane of polarization of incident light by a fixed angle determined by its structure, and is useful for the above purpose.

On the other hand, since the polarization rotation angle of a semiconductor waveguide type polarization rotation element is fixed depending on the structure, the angle of the plane of polarization of the optical signal from the optical fiber depends on the semiconductor waveguide type optical amplifier or semiconductor waveguide type. If a situation occurs in which the difference in the angle of the polarization plane suitable for the modulator is different from before, the semiconductor waveguide polarization rotator itself is replaced, the semiconductor waveguide polarization rotator is cut off, or other It was necessary to recreate a semiconductor waveguide type polarization rotator by adding a semiconductor waveguide and extending the waveguide.

[0004]

SUMMARY OF THE INVENTION The present invention has been proposed to improve the above-mentioned drawbacks, and its purpose is to change the polarization rotation angle in a conventional semiconductor waveguide type polarization rotation element. It is to solve the problem that is difficult.

[0005]

According to the present invention, there is provided a waveguide segment formed on a semiconductor substrate and having a sectional structure or a path asymmetrical with respect to an axis perpendicular to the light traveling direction. An optical waveguide element in which waveguide segments having a structure in which a segment structure is inverted left and right with respect to an axis perpendicular to the traveling direction of light are connected in a cascade at one or more periods, and all or a part of the waveguide segments The invention is characterized in that a semiconductor waveguide type polarization rotator having a heater capable of raising the temperature of the waveguide by energization in the vicinity of all or a part thereof. The semiconductor waveguide polarization rotator has a waveguide segment whose cross-sectional structure or path is asymmetric with respect to an axis perpendicular to the traveling direction of light, and the segment structure is reversed left and right with respect to an axis perpendicular to the traveling direction of light. Waveguide segments having a structure are connected in a cascade at one or more periods. When the waveguide cross-sectional structure and the curvature of the path are the same, to obtain the largest polarization rotation angle, the length L _opt of each waveguide segment
Must satisfy the following equation. L _opt = 1 / √ (δ ² + k ² ) where δ is the TE mode and T
The difference between the propagation constants of the M mode and k is the difference between the TE mode and the TM mode.
Coupling constant between modes. The actual length L of the waveguide segments polarization rotation angle of the shift when the polarization rotation element from L _opt is reduced.

[0006] As a result of examining the performance of the polarization rotation element, the inventors have experimentally confirmed that δ and k, which are characteristics related to the polarization rotation of the waveguide, greatly vary with temperature. A heater capable of raising the temperature of the waveguide by energization is installed near the waveguide of the conductive waveguide type polarization rotation element, and the temperature of the waveguide is raised by increasing the amount of current supplied to the heater, thereby increasing the δ of the waveguide. And k can be changed, so that the polarization rotation angle can be set to a different angle from before energization.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention provides a heater for raising the temperature of a waveguide by energizing near the waveguide of a semiconductor waveguide type polarization rotating element. The temperature is raised to change the polarization rotation angle of the waveguide, thereby changing the polarization rotation angle.

[0008]

An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a sectional view of a semiconductor waveguide manufactured to show the effect of the present invention. In FIG. 1, 1 is a waveguide core made of InGaAsP, 2 is an InP substrate (also serving as a waveguide clad), and 3 is a heater. FIG. 2 is a top view of the semiconductor waveguide. 4 is a signal light input end, 5 is a signal light output end, 6 is a quarter-arc first waveguide segment, 7 is a quarter-arc second waveguide segment, 8 is a heater, and 9 is a heater. This is a current input terminal to the heater. 10 is an input side linear waveguide,
Reference numeral 11 denotes an output side linear waveguide, and reference numeral 12 denotes an InP substrate. The path of the second waveguide segment is obtained by inverting the path of the first waveguide segment left and right with respect to the substrate normal direction perpendicular to the light traveling direction. Each waveguide segment has a length of 150 μm and is designed to have L _opt for light having a wavelength of 1.55 μm. In other words, the polarization rotation angle becomes maximum when no power is supplied to incident light having a wavelength of 1.55 μm.

This device was actually manufactured, and the wavelength was 1.55 μm.
When the polarization rotation angle of the incident light of
5 degrees. Next, when the heater was energized and the waveguide near the heater was heated, the polarization rotation angle was reduced. FIG. 3 shows the relationship between the amount of current injected into the heater and the polarization rotation angle. At the time of 200 mA injection, the polarization rotation angle is reduced to 20 degrees. This demonstrates that the present invention is effective in changing the polarization rotation angle without significantly recreating the semiconductor waveguide type polarization rotation element. Note that the heater may be arranged near all or a part of the waveguide segment.

[0010]

As described above, according to the present invention,
Since the polarization rotation angle of the semiconductor waveguide type polarization rotation element can be set freely within a certain range by the current injected into the heater, the polarization plane of the signal light having various polarization rotation angles can be changed to the semiconductor waveguide type optical amplifier. Or an angle suitable for a semiconductor waveguide type optical modulator.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a semiconductor waveguide polarization rotator manufactured to show the effect of the present invention.

FIG. 2 is a top view of a semiconductor waveguide polarization rotator manufactured to show the effect of the present invention.

FIG. 3 shows the relationship between the polarization rotation angle with respect to light having a wavelength of 1.55 μm and the current injected into a heater in a semiconductor waveguide type polarization rotation element manufactured to show the effect of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 Waveguide core made of InGaAsP 2 InP substrate (also serving as waveguide clad) 3 Heater 4 Signal light input end 5 Signal light output end 6 Quarter-arc first waveguide segment 7 Quarter-arc Second waveguide segment 8 Heater 9 Current input terminal to heater 10 Input-side linear waveguide 11 Output-side linear waveguide 12 InP substrate 13 In the semiconductor waveguide type polarization rotating element manufactured to show the effect of the present invention, Curve showing the relationship between the polarization rotation angle and the current injected into the heater

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Louis Wayne 3-19-2 Nishi Shinjuku, Shinjuku-ku, Tokyo Japan Telegraph and Telephone Corporation (72) Inventor Takayuki Yamanaka 3-192 Nishi Shinjuku, Shinjuku-ku, Tokyo No. Nippon Telegraph and Telephone Corporation (72) Inventor Kiyoyuki Yokoyama 3-2-1-2 Nishishinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (1)

[Claims] 1. A waveguide segment formed on a semiconductor substrate and having a cross-sectional structure or a path asymmetric with respect to an axis perpendicular to the light traveling direction, and the segment structure is formed with respect to an axis perpendicular to the light traveling direction. An optical waveguide element in which a waveguide segment having a horizontally inverted structure is connected in a cascade at one or more periods. A semiconductor waveguide type polarization rotating element comprising a heater capable of raising the temperature.