Amplification and compression of weak picosecond optical pulses by using semiconductor-laser amplifiers.

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 nearlylinear 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.