News | January 18, 2022

Researchers Proposed An All-Fiber-Laser-Pumped Mid-Infrared MgO:PPLN Optical Parametric Oscillator

MgO-doped periodically poled lithium niobate (MgO:PPLN) optical parametric oscillators (OPOs) have the ability to generate high-power mid-infrared (MIR) laser with high efficiency. They have important applications in the fields of atmosphere monitoring, laser spectroscopy, photoelectric detection, and remote sensing surveys. In particular, miniaturized high-power MgO:PPLN OPOs are of paramount importance.

Yb-doped fiber lasers (YDFLs) have the advantages of high power, high efficiency, small size, light weight, and excellent heat dissipation. Therefore, YDFL-pumped MgO:PPLN OPOs are easy to realize miniaturization and obtain high-power laser output.

Researchers from Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP) of the Chinese Academy of Sciences (CAS) have developed a miniaturized YDFL-pumped MgO:PPLN OPO with an output MIR power &GT5 W at 3.76 μm. By adopting the thermoelectric cooling configuration, the size of the whole miniaturized OPO is only 330 mm × 330 mm × 165 mm.

Recently, they have increased the MIR output power of YDFL-pumped MgO:PPLN OPO to &GT10 W. Related results were published in Optics & Laser Technology.

The linearly polarized all-fiber YDFL generates a pump laser at 1064 nm with one master-oscillation and three power-amplifier stages. The amplified pump laser outputs through the polarization-maintaining fiber collimator. After passing through a Faraday isolator and a lens group for reducing the pump waist, the pump laser is coupled into the MgO:PPLN crystal with the grating period of 29.5 μm. The resonant cavity used the signal-resonant and pump-double-pass scheme.

Via optimizing the pump repetition rate (300 kHz), pulse width (200 ns), and waist diameter (230 μm), the OPO can achieve a maximum MIR idler power of 10.82 W at 3.754 μm with a conversion efficiency of 13.68%. To the best of our knowledge, this is the highest MIR power above 3.7 μm reported thus far with the use of the fiber-laser-pumped MgO:PPLN-based OPO configuration. The corresponding M2 factors of the MIR laser along the horizontal and vertical directions are 2.98 and 2.08, respectively. The maximum total power (including signal and idler) of OPO reaches 35.4 W with a conversion efficiency of 44.75%.

Source: Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences