Design of cascaded gratings to be used in out-of-plane signal processing

In this paper we present the theoretical study and design of a GaAs-based guided-wave grating device for uniform out-coupling of optical power, to be detected on an external 2D plane. The model of diffraction is based on the exact solution of the relevant boundary-value problem. The device is formed by a number of cascaded gratings, each of them having different geometric characteristics. Simulations have been carried out at different values of grating thickness and number of cascaded gratings, in order to obtain the best performance in terms of diffraction efficiency and device transmissivity. Uniform distribution of the out-coupled power on a 2D region has been achieved by varying the groove depth of each cascaded gratings. This device can be successfully used to obtain uniform illumination of coupled-charge-devices in optical computing and signal processing applications, such as image restoring in synthetic aperture radar systems, spectral analysis, matrical multiplication, and so on.