Optimization of Single-Step UV Exposure for Fabrication of Integrated Optical Device by Imprinting

In this paper, a single ultra-violet exposure for multi-height structure was used to fabricate an optical-fiberintegrated planar lightwave circuit (PLC) splitter using a thermal imprinting technique. The 1 × 8 tapered multimode PLC splitter was designed with a trench at a depth of 50 μm and a variable width ranging from 50 μm to 690 μm for the insertion of waveguide and fiber structures measuring 125 μm × 87.5 μm in order to minimize insertion loss. Photolithography with a Cr layer and bottom anti-reflection coating (BARC) was utilized to fabricate a multi-height photoresist structure, and the effect of the thick Cr layer and BARC on the geometry was investigated. Scanning electron microscopy of the fabricated structures showed that a Cr thickness of 50 nm and BARC provided the ideal geometry with a minimal undercut and sidewall roughness. Based on the characterization of the imprinted splitter, the average value and uniformity of optical loss between the channels were 10 dB and less than 0.42 dB, respectively.