Design And Fabrication Of Superstructure Waveguide Gratings

Super-structure gratings have been widely used in devices of dense wavelengthdivision multiplexing (DWDM) systems due to its comb-like reflection spectrum.Multi-channel filters, dispersion compensators, multiplexer/de-multiplexers based onsuper-structure grating played an important role in DWDM systems. Super-structuregrating can be used in distributed Bragg reflector (DBR) semiconductor lasers to achievewidely wavelength tuning. Performances of super-structure grating devices are highlyrelated to the techniques of grating fabrication. Nanoimprint lithography (NIL) is one ofthe most potential nano-sclae patterning technologies of next generation, and it has beenwidely investigated because of its low-cost, high resolution and efficiency.A research on super-structure grating design and fabrication using nanoimprintlithography is carried out in this thesis. The detailed works are as follows:(1) The reflection spectrums of super-structure gratings are simulated based on amodel built by transfer matrix method. Planarization technology of reflection spectrum isdiscussed, and effects of grating parameters on its characteristics are discussed. Sampledgratings and digital concatenated gratings are then designed.(2) Improvements on conventional nanoimprint process are studied. Anti-sticktechnology and soft mold imprint are introduced to achieve large area uniform imprintedpatterns. An alignment method is developed to realize alignment of a soft mold and asubstrate.(3) Optimizations of control process of nanoimprint and inductively coupled plasma(ICP) etching, waveguide based super-structure gratings are demonstrated. Temperatureand pressure of nanoimprint are optimized, and gas ratio during ICP etching is optimizedas well. Finally sampled gratings and digital concatenated gratings are fabricated.