Design and performance of GaAs-based guided-wave heterodyne circuits for signal processing

In this work are presented the design parameters and performance of a guided-wave spectrum analyzer based on a multilayered ZnO/AlxGa1-xAs/AlyGa1-yAs/GaAs structure for heterodyne detection of spread spectrum signals. The adopted circuit configuration includes a double integrated collimating grating having non linear groove profiles, an acousto-optic Bragg cell, a concave frating lens, a focusing grating lens and an output photodiode array. The optical structure has been optimized as a function of the layer thickness, and Al title in order to obtain improved performance of the circuit in terms of 3-dB Bragg bandwidth (up to 185 MHz), surface acoustic wave power consumption (less than 3 mW), frequency resolution (less than 1.5 MHz), and single-tone dynamic range (about 56 dB). The number of channels has been found equal to 112 and 125 in the two structures under investigation, respectively. The calculated single- and double-tone dynamic range are reduced of about 40% with respect to the corresponding dynamic ranges of the homodyne architecture. All the design parameters have been calculated for each integrated component of the circuit at the free-space optical wavelength of 0.85 micrometers .