We present our last numerical and experimental results on a mid-infrared source based on a tunable Yb-based hybrid MOPA pump and a Backward Wave Optical Parametric Oscillators (BWOPO). The BWOPO has a record-low oscillation threshold of 19.2 MW/cm2 and generates mJ-level output with an overall conversion efficiency exceeding 70%. The BWOPO acts a frequency shifter of the pump radiation toward the forward wave, maintaining the pump spectral properties. The demonstrated tuning range of 10 GHz is already compliant for DIAL applications. We have also developed advanced numerical modelling of the BWOPO taking into account spectral and, for the first time, spatial beam profiles.
A highly efficient mirrorless OPO tunable in the mid-infrared around 2 μm has been developed and characterized in an original pumping configuration comprising a tunable high power hybrid Ytterbium laser MOPA (Master Oscillator Power Amplifier) in the nanosecond regime. The hybrid pump laser is based on a fiber laser seeder continuously tunable over several GHz at 1030 nm, which is shaped in the time domain with acousto-optic modulators (AOM), and power amplified in a dual stage Ytterbium doped fiber amplifiers, followed by two Yb:YAG bulk amplifiers. The pump delivers up to 3.5 mJ of energy within narrowband 15 ns pulses with a 5 kHz repetition rate. The output was focused into Periodically Poled KTP (PPKTP) crystals with a quasi-Phase Matching (QPM) period of 580 nm, producing Backward Optical Parametric Oscillation (BWOPO), with a forward signal wave at 1981 nm and a backward traveling idler at 2145 nm. We report significant optical to optical efficiencies exceeding 70 % depending on crystal length and input power. As theoretically expected, the forward wave could be continuously tuned over 10 GHz following the pump frequency sweep, while the backward wave remains almost stable, both being free from mode hops. These properties obtained from an optical arrangement without free-space cavities are attractive for future space Integrated Path Differential Absorption (IPDA) Lidar applications, which require robust and efficient tunable frequency converters in the mid-infrared. Additional presentation content can be accessed on the supplemental content page.
We present design and first performance results of an airborne differential absorption lidar laser transmitter that can measure CO2 and water isotopes at different wavelengths around 2 µm with the same setup. This laser will be integrated into an airborne lidar, intended to demonstrate future spaceborne instrument characteristics with high-energy (several tens of millijoules nanosecond-pulses) and high optical frequency-stability (less than a few hundreds of kilohertz long-term drift).
The transmitter consists of a widely tunable OPO with successive OPA that are pumped by a Nd:YAG MOPA and generates the on- and offline wavelength of the addressed species with narrow bandwidth.
We present a narrowband, non-resonant optical parametric oscillator based on 5-mm thick Rb-doped periodically-poled KTiOPO4 (PPKTP) operating in the high-energy/low repetition-rate regime. An uncoated volume Bragg grating (VBG) is employed as one of the cavity mirrors reflecting only the signal whereas the other cavity mirror is reflecting only the idler. Pumping by a Nd:YAG laser at 1.0642 μm in a double-pass, the signal plus idler output energy reached almost 5 mJ at a repetition rate of 100 Hz corresponding to a conversion efficiency of ⁓26%. Both signal and idler are narrowband with full width at half maximum (FWHM) of 0.5 nm at 1942 nm and 0.76 nm at 2355 nm, respectively.
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