Large aperture PPMgLN based high-power optical parametric oscillator at 38 µm pumped by a nanosecond linearly polarized fiber MOPA

Abstract

We report a large aperture PPMgLN based OPO generating 21W of average output power at a slope efficiency of 45%. The OPO is pumped with the output from a polarization maintaining Ytterbium doped fiber MOPA operating at 1060nm producing 20ns pulses at a repetition rate of 100kHz and an average output power of 58W (after the isolators). A maximum of 5.5W of optical power was recorded at the idler wavelength of 3.82µm without thermal roll-off. The pulse rise/fall time plays a significant role in the OPO conversion efficiency and that further enhancements in the efficiency should be possible using pulses with faster rise and fall times.

High-power PPMgLN-based optical parametric oscillator pumped by a linearly polarized, semi-fiber-coupled acousto-optic Q-switched fiber master oscillator power amplifier

“…We believe that the major cause of the thermal effect is the idler absorption that is unavoidable while the back conversion could be alleviated by optimizing the signal reflectivity. To alleviate the thermal roll-off problem, larger pump beam diameter [10] as well as thermal compensation methods such as semi-external-cavity structured OPO [18] should be taken into consideration under higher pump power.…”

“…According to these requirements, fiber lasers are supposed to be the best candidates among all the OPO pump sources due to their compactness, robustness, excellent beam quality, and simple thermal management schemes [3]. Therefore, fiber-laser-pumped OPOs have been extensively investigated from continuous wave (CW) to ultrashort pulsed operation schemes [4][5][6][7][8][9][10][11][12][13]. Among all these pump sources, fiber lasers with tens to hundreds of nanoseconds are particularly useful in outdoor applications for both environmental monitoring and missile countermeasures because simple linear cavities are applicable to such pump sources converting the pump power to idler output efficiently during each pulse with peak power higher than the CW OPOs and dimensions smaller than the synchronously pumped OPOs.…”

“…Among all these pump sources, fiber lasers with tens to hundreds of nanoseconds are particularly useful in outdoor applications for both environmental monitoring and missile countermeasures because simple linear cavities are applicable to such pump sources converting the pump power to idler output efficiently during each pulse with peak power higher than the CW OPOs and dimensions smaller than the synchronously pumped OPOs. Consequently, many experiments have been carried out on linearcavity-structured OPOs pumped by master oscillator power amplifier (MOPA) configured fiber lasers working in the nanosecond region so far [9][10][11][12][13].…”

“…Although an active pulse-shaping technique could enable the fiber amplifiers to eliminate the nonlinear effects and to compensate the gain saturation effect with enhanced conversion efficiencies in OPOs, the low average power of the seed lasers would require a chain of fiber amplifiers to boost the output power to tens of watts, which would make them less costeffective [9][10][11]. Our former experiment has demonstrated an improved OPO system pumped by a fully fiberized MOPA system with only one stage of amplification.…”

40 μm, high repetition rate periodically poled magnesium-oxide-doped lithium niobate mid-infrared optical parametric oscillator pumped by steep leading edge pulsed fiber laser

“…Researchers have spent much effort on generating a long wavelength, high repetition rate mid-IR laser in recent years. In [11] demonstrated a maximum average power of 5.5 W idler laser at the wavelength of 3.82 μm at 100 kHz with the efficiency of 9.48%. In 2013, Chen et al [12] reported an idler laser at 3.82 μm with an average output power of 3.27 W under the pump power of 25 W at 65 kHz.…”