JPS6194388A - Semiconductor laser element - Google Patents

Abstract

PURPOSE:To modulate an output from laser beams without changing injecting currents, and to obtain oscillating beams at a stable mode by electrically controlling a degree in which laser beams are coupled with an optical waveguide section adjacently arranged to a semiconductor laser section. CONSTITUTION:An InGaAsP optical waveguide layer 12, N<+>-InP 13, an InGaAsP active layer 21 and a P<+>-InP clad 14 are superposed on an N<+>-InP substrate 11, a P<+>-InP loading section is formed, and ohmic electrodes 16, 17 are attached. The active layer 21 and the clad layer 14 are buried to P-InP 19 and N-InP 20. Currents are injected from the electrode 16, beams emitted from the active layer 21 are laser-oscillated while crossing the waveguide layer 12, and there is a laser output even under the loading section 15 by distribution coupling. When constant currents are flowed through a laser section and the refractive index of a waveguide is changed by an electro-optic effect by utilizing a P-N junction under the loading section 15, coupling with the laser section varies, and an optical output from the laser section largely alters, thus acquiring oscillating beams at a mode more stable than normal direct modulation.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a modulation structure for a semiconductor laser device.

Conventional Structures and Problems The main modulation method for conventional semiconductor lasers is the direct modulation method, which is performed by changing the current injected into the active layer. However, changing the amount of current injection causes a change in oscillation mode due to a change in the refractive index of the laser section, which causes noise and the like. The conventional basic configuration example is the first
As shown in the figure. Here, 1 is an n-type semiconductor substrate, 2 is an active layer, and 3
is a P-type cladding layer, 4 is an ohmic electrode to the P-type layer, 5 is
is an ohmic electrode to the n-type substrate, and 6.7 are P- and n-type buried layers, respectively.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a semiconductor light emitting device that can modulate optical output without changing the carrier density injected into a semiconductor laser.

Structure of the Invention The present invention obtains modulated signal light by electrically controlling the degree to which laser light is coupled to an optical waveguide section disposed close to a semiconductor laser section.

DESCRIPTION OF EMBODIMENTS The configuration of a laser element according to an embodiment of the present invention will be described with reference to FIG. In the description, an InGaAsP-based semiconductor material is used for convenience, but the present invention is not limited to this material. FIG. 2 is a cross-sectional view taken in a direction perpendicular to the direction of the laser resonator. In FIG. 2, 11 is an n+-InP substrate, 12 is an InGILASP optical waveguide layer, and 13 is an n-InP substrate.
layer 21 is an InGaAsP active layer, 1a (dP+-In
P cladding layer, 16 is P-InP loading part, 16 is P+-
Ohmic electrode for InP cladding 14, 17P
An ohmic electrode 18 is for the +-InP loading section 15, an ohmic electrode 18 is for the n+-InP substrate 111C, and 19 and 20 are P and n-InP buried layers, respectively. Here, the laser light emitted by the current injected from the electrode 16 is distributed in the portion shown by the broken line in the figure. That is, the light emitted from the active layer 21 is emitted across the waveguide layer 12, causing laser oscillation. Further, since a waveguide is formed directly under the loading section 15 formed near the laser stripe, the laser output is also present under the loading section 15 due to distributed coupling.

Here, when a constant current is flowing through the laser section, the refractive index of the waveguide under the loading section is changed by electro-optic effect using the P-N junction formed at the bottom of the loading section 15. As a result, the optical output of the laser section changes significantly.

By utilizing this, it becomes possible to modulate the current injected into the laser section without directly causing it to ignite. Furthermore, by using a laser section that does not require an interfold surface, such as a DFB laser, application to optical integrated circuits becomes possible.

Effects of the Invention The output of semiconductor laser light can be modulated without changing the injection current, and oscillation light in a more stable mode can be obtained than in normal direct modulation.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional example of a semiconductor laser, and FIG. 2 is a sectional view of a semiconductor laser element according to an embodiment of the present invention. 11... n-type semiconductor substrate, 12 - optical waveguide layer,
13 - n-type semiconductor separation layer, 21- - active layer, 14
... P cladding layer, 15,15,16.1617.
17', 18...Ohmic electrode, 19°20
...Embedded layer. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (2)

[Claims] (1) A laser section having a light emitting function and an optical waveguide, at least a part of which is close to the laser section and parallel to the laser stripe, are formed on the same semiconductor substrate, and the propagation characteristics of the optical waveguide are electrically changed. A semiconductor laser device characterized in that the laser output is controlled by coupling laser light to the optical waveguide section. (2) A semiconductor according to claim 1, which has a laser section, characterized in that the semiconductor laser has an optical waveguide region that is sufficiently transparent for its oscillation wavelength in the vicinity of the active layer of the semiconductor laser. laser element.