Abstract
Red pulses with >30 mJ energy and <0.6 nm bandwidth have been demonstrated using a type 2 phase matched optical parametric oscillator pumped at 532 nm. A symmetrical signal beam with beam diameter-divergence product of ~3 mm•mrad was obtained by applying KTA and BBO crystals in the same resonator
Highlights
Remote sensing applications often require high energy laser-like beams with narrow bandwidth and low divergence at wavelengths that cannot be reached directly with ordinary laser materials
For the new beam to be generated with high conversion efficiency and good beam quality, careful design of the nonlinear optical conversion stage is necessary, in particular with respect to beam size, nonlinear crystal length, and in the case of an optical parametric oscillators (OPOs), resonator length and output coupling
If the pump fluence is restricted to 1 J/cm2 to avoid optical damage, we find that good beam quality can be expected from this OPO only if the pump energy is limited to ≈15 mJ
Summary
Remote sensing applications often require high energy laser-like beams with narrow bandwidth and low divergence at wavelengths that cannot be reached directly with ordinary laser materials. Unstable resonators can improve the beam quality at the expense of the conversion efficiency [2] Another approach is to use the natural filtering of the signal far field that is a result of the limited acceptance angle of the nonlinear process in the OPO. In this work we have used another approach in which the far field is improved in both directions (and the beam asymmetry is reduced) by using two different nonlinear crystals in the same OPO [7] Both crystals are type 2 phase matched for the same set of wavelengths, but with orthogonal critical planes the far field narrowing occurs in both directions
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