An integrated-optical approach to the Fourier transform

A wide-band real-time spectrum analyzer is examined as a viable integrated optical circuit for processing electronic signals. The spectrum analyzer includes a Luneburg beam expansion lens system, a surface elastooptic Bragg spatial modulator, reflectors, a Luneburg Fourier-transform lens, and a waveguide coupled photodetector array, all formed on thermally grown SiO2on Si as the substrate. A distributed-feedback (GaAl)As laser with hybrid coupling is included as the carrier for the optical Fourier transform. The developmental status of this integrated-optical spectrum analyzer and its essential design considerations are delineated.