SPLTRAK Abstract Submission
Optical Design Considerations for Thin Photonic Power Converters with Textured Back Reflector
Neda Nouri, Christopher E. Valdivia, Meghan N Beattie, Jacob J Krich, Karin Hinzer
SUNLAB, Centre for Research in Photonics, University of Ottawa, Ottawa, ON, Canada

Photonic power converters (PPCs) are a main component of power over fiber and power beaming systems, generating electrical power from narrow-band illumination. Ultra-thin PPCs reduce material use, enable flexible devices, and increase maximum efficiency via light management. In recent years, considerable research has focused on incorporating a back reflector (BR) in thin PPCs, forming an optical cavity between the BR and PPC layers. This light trapping creates tunable resonances in the absorptance spectrum that can be aligned at the target wavelength by variation of design space parameters. In this study, we discuss optical design considerations of thin InAlGaAs PPCs with integrated pyramidal nano-textured BRs under 1310 nm illumination. Simulations with finite difference time domain method in conjunction with particle swarm optimization revealed that guided mode resonances induced by the textured BR can yield up to an 8-fold reduction in absorber layer thickness compared to an optically thick PPC on an InP substrate with the same absorptance. Multiple combinations of design space parameters yield similar total absorptance at 1310 nm but with different absorptance spectra. Among all designs, those with overlapping resonances around the target wavelength with an added antireflection coating layer were the least sensitive to variations in the illumination wavelength. A tolerance study of an optimized design showed that a 70 nm variation in device thickness can shift BR induced resonances from constructive to destructive interference and a 50 nm variation of the height and base width of nano-pyramids drops absorptance by more than 30% (absolute) which illustrates the precision required in the fabrication of high efficiency ultra-thin PPCs.