Grating coupled vertical cavity optoelectronic devices

DETAILED DESCRIPTION A semiconductor laser or detector has been invented which is a vertical cavity device constructed with a dual dielectric top Distributed Bragg Reflector (DBR) mirror wherein a diffraction grating in the second order is incorporated into the dielectric layer which is the first layer to be deposited upon the vertical cavity.
The function of the grating is to change the direction of propagation of the light from vertical to horizontal so that the output of the vertical resonant cavity is a mode in a waveguide.
In general, as a laser it is desired to launch optical power primarily in one direction so that an asymmetry or blaze angle will be incorporated into the grating.
Therefore the principle of operation is based on the diffraction of light produced by the vertical cavity laser into an optical mode which propagates in the guide.
The polarization of the light is dictated by the polarization in the guide which itself is TE in general because of the higher diffraction efficiency for TE light.
The light propagating in the guide also diffracts into the vertical cavity and reinforces the polarization of the vertical cavity emission through the process of stimulated emission.
The device is designed so that the vertical emission is essentially inhibited and the device output is totally diffracted waveguide output and therefore the power output can be increased by simply extending the laser in length within the constraint of chip size.
The grating structure may be applied to realize modulators, detectors and amplifiers in addition to lasers.
The device is described in one illustrative embodiment of the HFET inversion channel laser, which comprises one of the laser devices in the general family of inversion channel optoelectronic devices which are modulation doped devices.
In this form of the invention, a refractory metal emitter provides a conduction path of hole flow into the laser active region by two-dimensional conduction.
The two dimensional contour of the conduction path is established by an N type implant under the metal emitter