Tunable Mid-Infrared Continuous-Wave Optical Parametric Oscillator Based on Fan-Out Grating PPLN Pumped at 1064 nm

Summary form only given. Recently, a variety of mid-infrared (mid-IR) light sources have been developed for use in remote sensing applications such as biomedical sensing, optical radiation measurement, gas sensing, planetary monitoring and defense science [1]. In particular, continuous-wave (cw) optical parametric oscillator (OPO), which is capable of wide wavelength-tuning and has a narrow linewidth, are known to useful in the mid-IR applications. For example, to achieve performance evaluation of mid-IR spectrometer, which is indispensable for the success of the remote sensing applications, it is essential to develop a light source with a wide wavelength tuning bandwidth and a narrow linewidth. However, because of the absorptive property of the PPLN medium at mid-IR, the use of cw OPO based on PPLN has been limited to more than 4.7 μm [2]. In this paper, we report on a tunable 2.5 - 5.0 gm continuous -wave optical parametric oscillator based on fan out grating PPLN pumped at 1064 nm. Figure 1(a) represent the experimental schematics for producing tunable mid-IR OPO output. Since the mirror coating is difficult to cover the idler wavelength from 2.5 gm to 5.0 gm, there are OP01, which produces idler outputs from 2500 nm to 3600 nm, and OP02, which produces idler outputs from 3600 nm to 5100 nm, respectively. To reduce the operating threshold for starting OPO oscillation, we install a standing -wave cavity resonating both at the pump and signal wavelengths [3]. By using the modified PoundDrever-Hall (PDH) technique, the cavity length is stabilized to resonance of the pump laser [4]. The idler wavelengths are achievable with changing the grating period of the fan -out PPLN crystal