Pulse Compression in Single-Mode Fibers—Picoseconds to Femtoseconds

Abstract

The compression of frequency swept (in time) or “chirped” optical pulses was independently proposed by Gires and Tournois (1964) and Giordmaine et al. (1968). Optical pulse compression is the optical analog of microwave pulse compression or chirp radar developed by Klauder et al. (1960). The compression is accomplished in two steps. First, an optical frequency sweep is impressed on the pulse. The next step is the compensation of this frequency sweep by using a dispersive delay line, where the group velocity or group delay varies with optical frequency. Ideally, the dispersive delay line would impress the opposite chirp on the pulse, resulting in the compression of the pulse to its minimum width, ~ 1/Δω, where Δω is the frequency sweep. Treacy (1968, 1969) was the first to recognize that a pair of diffraction gratings was a suitable dispersive delay line for a linearly chirped pulse; he used gratings to compress the inherently chirped output of a mode-locked Nd: glass laser. Similar experiments were later performed by Bradley et al. (1970). Duguay and Hansen (1969) used an LiNbO₃ phase modulator and Gire-Tournois interferometer to compress pulses from a mode-locked He-Ne laser.