SBIR-STTR Award

This STTR Phase I project will develop a waveguide grating filter device with enhanced performance that can meet the needs of most complex WDM systems. This filter will then be coupled to an external laser source to form a hybrid optical module with tunable wavelength for a number of practical applications. This new technology, developed in conjunction with the University of Florida, will then be transferred to Advanced Photonics Technology Inc. for further refinement to a precommercial level. Wavelength-selective filters in the integrated-optic embodiment are the most promising candidates for deployment in Wavelength-Division-Multiplexed networks. A waveguide grating filter appears to be very promising on account of its extreme wavelength sensitivity and compactness. However, the performance of practical devices has thus far been severely limited by the lack of high-reflectance waveguide gratings. The unique feature of the proposed effort in achieving high-reflectance gratings is the use of a Silicon overlayer to substantially perturb the mode index of an optical waveguide underneath it without adding an additional mode loss. Silicon has been selected on account of its large refractive index, processibility, and low cost. The primary commercial application of waveguide grating filters is in Wavelength-Division-Multiplexed networks. Another most important application is the development of compact and efficient waveguide lasers and amplifiers.

The primary goal of the completed Phase I effort was to prove the feasibility of hig-reflectance low-loss silicon gratings on LiNbO3 waveguides. We showed theoretically and demonstrated experimentally that a substantialperturbationof the effective mode index ina LiNbO3 waveguide can be achieved with a high-index Si overlay without increasing optical loss for the guided mode. This phenomenon was used to build a high performance Si Distributed Bragg reflector with 80% reflectivity. Subsequently, a narrowband asymmetric Fabry-Perot filter with electro0optical tunability was realized using a Si grating on a LiNbO3 waveguise. The filter was tested in a hybrid laser-filter module. The developed technology of high performance DBR gratings using Si-on-LiNbO3 structures is useful in developing a variety of advanced devices, in particular, filters and compact waveguide laser sources, such as CW, mode locked, Q-switched, and tunable lasers. These devices are sorely needed inthe cable and telecommunication industry, especially in WDM networks.