JPS6396982A - Optical integrated circuit - Google Patents

Abstract

PURPOSE:To feedback part of a light irradiated from an active layer by a diffraction grating and to irradiate the part of the light perpendicularly to a semiconductor substrate thereby to eliminate the displacement of the position of a condensed spot of the irradiated light by integrating an active region including at least the active layer and a two-dimensional optical wave guide having a diffraction grating on the substrate. CONSTITUTION:An n-type AlGaAs clad layer 12, an n-type GaAs active layer 13, a p-type AlGaAs clad layer 14 and a P<+> type GaAs cap layer 15 are laminated on an n-type GaAs substrate 11 to form an active region 16 of buried structure. A diffraction grating 17 is formed on a two-dimensional optical wave guide 18. The light irradiated from the region 16 is coupled with the wave guide 18 to be conducted, the light of specific wavelength determined by the pitch by the grating 17 is fed back to the region 16 to be oscillated in a single mode in the wavelength. The light of the specific wavelength is partly irradiated perpendicularly to the substrate 1 by the grating 17. Since the stable single mode oscillation is generated, even if the irradiated light is condensed, the displacement of the spot does not occur.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical integrated circuit that can be used as a pickup for optical discs, optical information processing, etc.

Conventional technologyCurrently, optical disk pickups are composed of microscopic optical elements, but optical integrated pickups have been proposed to reduce weight and size2 and simplify the manufacturing process (References, Linings, IEICE Report, 0QE85-72.P, 3G).

FIG. 3 shows a schematic diagram of the optical integrated pickup.

Light emitted from a semiconductor laser 3 propagates through a dielectric guide waveguide 2 formed on an St substrate 1 , and a focusing grating coupler 4 emits a condensing light beam to the outside, which is irradiated onto an optical disk 6 . The light reflected by the surface of the disk returns to the grating focusing lens 4 and propagates again toward the entire light source of the leading waveguide. Then, the propagation direction of the light is changed by a focusing beam splitter 6 installed on the surface of the optical waveguide, and the light is focused on two pairs of light receiving elements 7.

Problems to be Solved by the Invention The optical integrated pickup described in the above-mentioned prior art is effective in reducing the size and weight of the optical system, but when the reflected light from the disk surface is returned to the semiconductor laser, The influence of the beam causes the oscillation spectrum of the semiconductor laser to become multi-mode or mode hopping, and the focused spot also becomes multi-mode or jumps in position, causing tracking failure. Also, since it is a hybrid configuration,
Coupling efficiency was low.゛Means for Solving the Problems The optical integrated circuit of the present invention has a structure in which an active region including at least an active layer and a two-dimensional optical waveguide having a diffraction grating are integrated on a semiconductor substrate, and the diffraction grating is Seven parts of the light emitted from the active layer are returned to the active layer to form a distributed reflection semiconductor laser, and a part of the light emitted from the active layer is configured to be emitted in a direction perpendicular to the substrate; The diffraction grating may have a concentric shape centered on the coupling portion between the active layer and the two-dimensional optical waveguide, and the two-dimensional optical waveguide may have a region between the active region and the diffraction grating that functions as a lens. The structure may be such that the light emitted from the active region is guided to the diffraction grating as parallel light.

Operation The present invention is a so-called distributed reflection type laser that performs laser oscillation by feeding back light emitted from the active layer by a diffraction grating due to the above-described configuration. A portion of the light emitted from the active layer is efficiently emitted by the diffraction grating in a direction perpendicular to the substrate. Since this semiconductor laser emits stable single-longitudinal mode oscillation without mode hopping, the spot where the light emitted to the outside of the substrate is focused performs stable operation without positional deviation.

Embodiment FIG. 1 shows a sectional view of the first embodiment of the present invention. t11 is n.
-GaAs substrate, 12 is n-AeGaAs cladding layer, u-GaAs, l'iI layer 13,
A region 16 having a p-AlGaAs cladding layer 14 and a p"-GaAs cap layer 15 is an active region. In this example, the active region 16 has a buried structure. Reference numeral 17 is a diffraction grating, and 18 is a two-dimensional optical waveguide. The diffraction grating 17 is
This is a secondary circuit lattice formed in concentric circles with the same pitch centered on the coupling portion between the active region 16 and the optical waveguide 18.

The light emitted from the active region 16 is coupled to and guided by the two-dimensional optical waveguide 18, and only the light of a specific wavelength determined by the pitch is fed back to the active region 16 by the diffraction grating 17, causing single mode oscillation at that wavelength. conduct. A portion of the light of a specific wavelength emitted by the active region 16 is emitted by the diffraction grating 17 in a direction perpendicular to the substrate 11 . In this example, stable single-mode oscillation was performed, so even when the light emitted to the outside was focused, stable operation was obtained without any positional shift of the focused spot due to wavelength changes.

FIG. 2 is a cross-sectional perspective view of a second embodiment of the invention. The two-dimensional optical waveguide 18 includes an active region 16 and a diffraction grating 2o.
In between, there is a region 21 that functions as a GaAs+ lens. In this embodiment, the light emitted from the active region 16 enters the two-dimensional optical waveguide 18 and spreads, but the lens region 21
It becomes parallel light and is guided to the diffraction grating. Diffraction grating 20
is formed in a straight line in order to return the first-order diffracted light to the active region and emit the twenty-first-order diffracted light in a direction perpendicular to the substrate 11.

As in this embodiment, the diffraction grating for the area that functions as a lens may be a linear one that is easy to tabulate, and the yield is also improved.

In the above two embodiments, a G a A a semiconductor is used, but a different material may be used depending on the desired wavelength, and a dielectric material may be used as the guide waveguide.

Effects of the Invention As described above, in the present invention, the diffraction grating serves as a distributed reflector that returns light emitted from the active layer to the active layer.
Single mode oscillation is performed at a specific wavelength corresponding to the period of the diffraction grating. This diffraction grating also functions as a coupler that emits light to the outside, allowing efficient output. Since it is a single mode oscillation, when the output is focused, the spot is single and there is no position shift due to mode hopping.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an optical integrated circuit according to a first embodiment of the present invention;
FIG. 2 is a partially sectional perspective view of an optical integrated circuit according to a second embodiment of the present invention, and FIG. 3 is a perspective view of a conventional optical integrated circuit. 11゛... Semiconductor substrate, 13... Active layer, 1e... Active region, 17, 20...
・Diffraction grating, 18... Two-dimensional optical waveguide, 21.
...Lens area. Name of agent: Patent attorney Toshio Nakao and 1 other person +1
--1↑base1 basic obscene a-:-shimeζU [-Pupini 8th 2nd figure

Claims (3)

[Claims] (1) A structure in which an active region including at least an active layer and a two-dimensional optical waveguide having a diffraction grating are integrated on a semiconductor substrate, and the diffraction grating redirects a part of the light emitted from the active layer to the An optical integrated circuit comprising means for returning part of the emitted light to an active layer to constitute a distributed reflection semiconductor laser and emitting part of the emitted light in a direction perpendicular to the substrate. (2) The optical integrated circuit according to claim 1, wherein the diffraction grating on the two-dimensional optical waveguide is formed concentrically with the coupling portion between the active layer and the two-dimensional optical waveguide as the center. (3) The two-dimensional optical waveguide has a region between the active region and the diffraction grating that functions as a lens, and the light emitted from the active region is guided to the diffraction grating as parallel light. Optical integrated circuit.