High-performance amplification of coherent ∼25-ns light pulses from a tunable source operating at ∼840 nm with bandwidth near the Fourier limit

In this paper, we have developed a high-performance injection-seeded optical parametric oscillator (OPO) based on periodically poled KTiOPO₄ (PPKTP). Because this NLO approach does not entail population inversion and avoids associated refractive index variations, it generates narrowband tunable light pulses at ~840 nm with <5 muJ energy. These have well-characterized shot-to-shot frequency stability and minimal frequency chirp, operating near the Fourier-transform (FT) limit imposed by the pulse duration of 25 ns. It is necessary to characterize and minimize frequency chirp effects that are due to time-dependent optical phase variations during the OPO pulse and in subsequent amplification and upconversion stages.