Physics of elliptical reflectors at large reflection and divergence angles I: Their design for nano-photonic integrated circuits and application to low-loss low-crosstalk waveguide crossing

Compact and Fabrication-Tolerant Waveguide Bends Based on Quadratic Reflectors

“…Compared to planar TIR mirrors, quadratic (elliptical or parabolic) reflectors offer more degrees of freedom to avoid incomplete reflection and contribute to further reduced loss and back reflection [43]- [45]. A parabolic reflector design has been exploited as a means to realize compact ring laser cavities in III-V materials [46], [47].…”

“…While the elliptical reflector design minimizes mode leakage, it creates an asymmetric light intensity distribution in the reflected beam which ultimately bounds the coupling efficiency [43], [44]. This limitation can be circumvented by cascading two quadratic reflectors such that the second reflector again mirrors the intensity profile and hence compensates for the asymmetry.…”