Design of a visible light photonic chip for Haar transform based optical compression

An optical chip has been designed and simulated using low contrast optical waveguide structures with the aim of investigating all-optical data compression in the visible spectrum. The chip comprises optical circuits for digital compression at wavelength λ = 532 nm (green light) based on the optical Haar transform (HT). Each circuit contains one or more 2-point HT building block(s), based on multimode interference (MMI) structures, which enables HT operation on the input signal pairs. Each of the two Outputs of each building block represents the sum and subtraction of the input signals. Compression can be achieved only by considering the sum signal and eliminating the subtraction signal. Higher order HT and, as a result, a higher rate of compression has been realized in the chip by implementing HT on the sum signals obtained from the first step compression. Simulation results obtained by three-dimensional beam propagation method (3D-BPM) show that designed circuits in the chip have an excellent capability for the realization of all-optical compression in the visible spectrum based on Haar transform.