Optimal design of microscaled scattering optical elements

A method of inverse design is applied to generate an optical device that acts as a wavelength demultiplexer. The ultracompact device, only 2μm thick, is designed to separate two wavelengths 1.55μm and 1.50μm, respectively, and consists of five layers of 0.4μm×0.4μm square-shaped bars etched in gallium arsenide. The expected cross talk is suppressed below −25dB for both wavelengths. The proposed device is an example of a scattering optical element, a name here introduced to define a class of computer-generated optical devices and whose functionalities are based on the multiple scattering by their individual constituents. For realization of the aforementioned devices, two-dimensional photonic plates can be prepared by only a single integrated circuit processing procedure followed by micromanipulation assembling.