Inverse designed broadband on-chip photonic couplers and polarization-independent wavelength demultiplexing

The recently emerged inverse design methods have become a widespread tool to address some of the bottlenecks in photonic devices. Consequently, increasing the functionality and efficiency of many designs are feasible with the judicious formulation of the inverse design. In the present work, different versions of inverse design methods are applied to obtain an integrated on-chip lens to focus broadband incident light between 1300 nm and 1750 nm. In another study, 1x2 polarization-insensitive wavelength selective structure made of a low-refractive-index material is investigated. The successful separation of 1300 nm and 1550 nm irrespective of the polarization type (either transverse-electric, TE, or transverse-magnetic TM) is achieved. Taking advantage of the design with a low refractive index material, the structural dimensions are scaled and 3D printed versions are used in the experiment to prove the operating principles of the designs and demonstrate the good agreement between the numerical and experimental data. Efficient integrated light couplers and polarization-independent wavelength selective devices hold great potential to be an integrated part of photonic devices. Inverse design approaches will continue to improve the efficiency of conventional building blocks of integrated photonics devices and help the realization of novel nanophotonic structures.