Abstract

Various microwave photonic processors using rare-earth-ion-doped crystals are under development, driven by the multi-GHz bandwidth and sub-MHz resolution potential of these crystals. Exploiting the available wide spectral band has long been a challenge, and only recently have some applications succeeded to. These include spectral analysis, range-Doppler processing. In these processors, the wide band advantage requires laser chirps covering the desired bandwidth in a few milliseconds with a precision better than the resolution aimed at. This is challenging. However in these applications one need not the chirp to be phase coherent all along its duration. Indeed, no phase relation need be conserved between the different frequency classes. Some coherent processing schemes require such phase relation. One of these is the so called photon echo chirp transform process [1], which can be used for instantaneous spectral analysis, compressive receivers, and also for arbitrary waveform generation. Up to now no convincing wide band demonstration could be performed of this coherent spectral process, because producing phase coherent, GHz-wide optical chirps of a few microseconds duration only is very challenging. We present here the first wide band and high resolution demonstration of the chirp transform algorithm. Because it is performed with a frequency agile laser source, this demonstration truly opens the way to the wealth of wide band spectral coherent processes that rare-earth ion doped crystals can handle.

© 2007 IEEE