Production of pairs of synchronized pulses by optical parametric generation and oscillation using aperiodically poled lithium niobate.

We report two sources of synchronized pairs of pulses based on optical parametric generation (OPG) and oscillation (OPO) that use aperiodically poled lithium niobate (APLN) as the nonlinear medium. The main purpose of these sources is to obtain terahertz radiation through difference-frequency generation. The APLN crystal was designed to generate two signals with their corresponding idlers from a single pump pulse; the signal wavelengths are around 1450 nm, and the frequency difference between them is tunable between ∼1 and 10 THz. In the OPO configuration, pumped by a Q-switched Nd:YAG laser (12 ns FWHM, 13 mJ), we obtain pairs of synchronized signals (∼5  ns FWHM) with a combined energy of 740 μJ; each signal has a bandwidth of <105  GHz. In the OPG configuration, we use a Q-switched Nd:YLF laser that emits shorter pulses (1.6 ns FWHM, 350 μJ), obtaining synchronized signal pulses with a combined energy of 38 μJ; each signal has a pulse width of 0.8 ns and a bandwidth of <175  GHz. The advantages of these sources for difference frequency generation are discussed.