PHASE GRATING MASKS FOR PHOTONIC INTEGRATED-CIRCUITS FABRICATED BY E-BEAM WRITING AND DRY-ETCHING - CHALLENGES TO COMMERCIAL APPLICATIONS

Near field holography is a method of using grating photomasks in which the m = -1 and m = 0 diffracted beams of a UV source interfere to for m a standing wave pattern. This simple hologram can then be used to ex pose a grating pattern on a process wafer when held in near- contact. This technique is especially attractive for use in OEICs and PICs when fabrication of the grating masks is accomplished with e-beam lithogra phy and dry etching, since the diffractive properties of the mask can be controlled by the physical parameters of the mask. The grating peri od on masks made in this way can be precisely controlled to produce ar rays of lasers each separated by only a small change in frequency (ord er 100 GHz) as may be required for WDM applications. We review the phe nomenology of fused silica phase grating masks and describe work towar d establishing characterization criteria, implementing practical print ing methods, improving e-beam precision, and demonstrating laser array performance. We discuss principle issues and progress in each of the technical areas.