EXTERNAL CAVITY LASER IN THIN SOI WITH MONOLITHIC ELECTRONICS

摘要

An ECL laser structure utilizes an SOI-based grating structure coupled to the external gain medium to provide lasing activity. In contrast to conventional Bragg grating structures, the grating utilized in the ECL of the present invention is laterally displaced (i.e., offset) from the waveguide (in most cases, a rib or strip waveguide) comprising the laser cavity. The grating is formed in an area with higher contrast ratio between materials (silicon and oxide) and thus requires a lesser amount of optical energy to reflect the selected wavelength, and can easily be formed using well-known CMOS fabrication processes. The pitch of the grating (i.e., the spacing between adjacent grating elements) and the refractive index values of the grating materials determine the reflected wavelength (also referred to as the "center wavelength"). A thermally conductive strip is disposed alongside the grating to adjust/tune the center wavelength of the grating, where the application of an electric current to the thermally conductive strip will heat the strip and transfer this heat to the grating. The change of temperature of the grating will modify the refractive indexes of the grating materials and as a result change its center wavelength.