Compact, cost-effective and high power mid-infrared (MIR) optical parametric oscillator (OPO)

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We will demonstrate a low repetition rate continuously-tunable optical parametric oscillator (OPO) operating in the mid-infrared (MIR) spectral region. An OPO is a light source similar to a laser, also using a resonator, but based on optical gain from parametric amplification in a nonlinear crystal rather than from stimulated emission. A main attraction of OPOs is that the signal and idler wavelengths can be varied in wide ranges. Thus, it is possible to access wavelengths in the MIR, far-infrared or terahertz spectral region. This makes OPOs very valuable for potential applications in biomedical, security, defense, and environment monitoring. In terms of environmental monitoring, robust portable MIR sources with high wall-plug efficiencies and small dimensions are required, something that OPOs can offer. Despite their amazing capabilities, OPOs have so far not found widespread use as commercial products due their complexity. Society and research communities can reap the benefits of successful research studies on developing compact and robust OPOs. In our collaborative project with O/E-Land Inc., our goal is to develop a compact and robust OPO system. More specifically, the wavelength of the OPO will be controlled by translating a fan-out PPMgLN crystal in a low finesse intracavity Fabry-Perot. The OPO will be pumped by a master oscillator power amplifier (MOPA) structure fiber laser with excellent characteristics. The pump pulses from the MOPA will have a rectangular shape, which is theoretically proved to improve the OPO's performance, compared with the Gaussian pump pulse. The seed of MOPA generates tunable optical pulses from 250 ps to 1ns duration using a 1064 nm band gain-switched laser diode pulse oscillator. A passive FBG will be introduced in the MOPA to reshape the input pulse to maximize the average output power and efficiency of the MOPA. Consequently, it is expected that the MOPA's average output power will be doubled thus enabling more average power in the MIR. This compact MIR source will have important applications in various sectors of human activities from manufacturing, biomedical, security, and defence.