Amplification and compression of weak picosecond optical pulses by using semiconductor-laser amplifier,” Opt

A novel pulse-compression scheme is proposed and demonstrated for compressing weak picosecond pulses having energies as small as 0.1 pJ. A semiconductor-laser amplifier is shown to impose a nearly linear frequency chirp on the pulse as a result of self-phase modulation occurring because of gain-saturation-induced index changes. The amplified chirped pulse can be compressed by passing it through a dispersive delay line. The theory shows that, depending on the operating conditions, the pulse width can be reduced by a factor of-2-4 and the peak power can be enhanced by a factor of-10-100. The preliminary experimental results are in agreement with theory. The use of optical fibers for pulse compression has become widespread in recent years.1 ' 2 When an in-tense optical pulse propagates down a fiber, the non-linear phenomenon of self-phase modulation (SPM) imposes a nearly linear frequency chirp across the pulse. The chirped pulse can be compressed by pass-ing it through a dispersive delay line such as a grating pair3 or a dispersive medium having anomalous group-velocity dispersion (GVD). Because of a relativel