Experimental investigation of dual wave optimized reflector stacks in solidly mounted resonators

Optimizing the reflector stacks for both longitudinal and shear waves is critical in the design of SMRs for high Quality factor (Q) filters. In this work, we experimentally investigate two design approaches for reflector stack optimization, i.e. the phase error approach and the diffraction grating method (DGM). Various SiO2/W reflector stacks were fabricated and analyzed: one stack using DGM and four others using the phase error approach. The extracted ID Q shows the expected trend except for the quarter-wave like stack. 2D FEM simulations reveal that the quarter-wave stack with an increased top-oxide layer shows improved shear reflection. The DGM stack showed the highest experimental Q of 1700. The results indicate that these approaches are applicable for any reflector stack combination.