Research on Mid-Infrared Parametric Oscillators - Part 01

Research on Mid-Infrared Parametric Oscillators - Part 01

1. Introduction

Lasers in the 3–5 μm band occupy an atmospheric window and have significant applications in laser communication, atmospheric monitoring, and laser medicine. Optical parametric oscillation (OPO) technology, as an important means of realizing mid-infrared lasers, offers advantages such as compact size, wide wavelength tuning range, and high efficiency. Currently, nonlinear crystals capable of generating 3–5 μm mid-infrared lasers include ZnGeP₂ (ZGP) and MgO:PPLN (www.wisoptic.com). However, ZGP crystals exhibit high absorption for lasers below 2 μm, requiring cascaded pumping to generate lasers larger than 2 μm for pumping. MgO:PPLN crystals, employing quasi-phase-matching technology, possess high nonlinear coefficients and high optical-to-optical conversion efficiency, and can be pumped with 1 μm lasers, achieving miniaturized, high-power mid-infrared laser output.

Because solid-state pulsed lasers have high peak power, most traditional mid-infrared MgO:PPLN-OPO pump sources are implemented by pumping MgO:PPLN with a 1 μm solid-state laser. In 2007, Zhao Wei et al. used an LD-pumped Nd:YVO₄ (www.wisoptic.com) laser as the pump source and achieved 1493–1538 nm tunable laser output using an intracavity OPO. In 2010, Peng Yuefeng's research group at the China Academy of Engineering Physics used a continuously pumped 1064 nm acousto-optic Q-switched oscillator to pump an OPO based on MgO:PPLN crystal, obtaining a 22.6 W 3.86 μm mid-infrared laser.

In 2023, Gao Baoguang et al. from the Aerospace Information Research Institute of the Chinese Academy of Sciences used a high-beam-quality electro-optic Q-switched 1064 nm fundamental frequency optically pumped an OPO based on MgO:PPLN with a polarization period of 29 μm, achieving a peak power of 48.45 kW 3.93 μm laser output. Also in 2023, Liu Shuai et al. from Tianjin University used a self-built 1 kHz nanosecond-level 1064 nm laser as the pump light, and pumping an OPO based on MgO:PPLN, a 4.08 μm mid-infrared laser output with a single pulse energy of 1.104 mJ was achieved.