Using multiple mutually incoherent fiber lasers to pump a coherent signal beam in an optical parametric oscillator

Although the concept of using multiple pumps to drive an optical parametric oscillator (OPO) is old, experimental evidence bearing on this possibility has been reported only recently. Periodically poled lithium niobate (PPLN) has recently been applied to the construction of efficient CW singly resonant optical parametric oscillators with a single collinear pump beam. Here we use three-dimensional numerical modeling to study the possibility of noncollinearly pumping a PPLN OPO using N CW fiber lasers. Our results suggest that a tunable signal whose power exceeds that of a single pump laser may be possible. The modeling reported here does not take thermal lensing into account, and so is appropriate for a situation where the average pump power is reduced by a mechanical chopper or where thermal effects are mitigated by a technique such as beam scanning. The modeling also assumes the availability of 40 W polarized fiber lasers operating at λ_p=1.064 μm and of 1 mm thick PPLN, whereas 20 W polarized fiber lasers and 0.5 mm thick PPLN are the current state-of-the-art. We suppose that the nonlinear grating period in the 5 cm long PPLN is chosen to quasi-phase-match signal and idler wavelengths λ_s=1.5 μm and λ_i=3.66 μm