We present a differential absorption lidar (DIAL) laser transmitter concept designed around a Nested Cavity Optical Parametric Oscillator (NesCOPO) based Master Oscillator Power Amplifier (MOPA). The spectral bands are located around 2051 nm for CO₂ probing and 1982 nm for H₂¹⁶O and HD¹⁶O water vapor isotopes. This laser is aimed at being integrated into an airborne lidar, intended to demonstrate future spaceborne instrument characteristics: high-energy (several tens of mJ nanosecond pulses) and high optical frequency stability (less than a few hundreds of kHz long term drift). For integration and efficiency purposes, the proposed design is oriented toward the use of state-of-the-art high aperture periodically poled nonlinear materials. This approach is supported by numerical calculations and preliminary experimental validations, showing that it is possible to achieve energies in the 40–50 mJ range, reaching the requirement levels for spaceborne Integrated Path Differential Absorption (IPDA) measurements. We also propose a frequency referencing technique based on beat note measurement of the laser signal with a self-stabilized optical frequency comb, which is expected to enable frequency measurement precisions better than a few 100 kHz over tens of seconds integration time, and will then be used to feed the cavity locking of the NesCOPO.

We present a tunable (6.62-11.34 µm), singly-resonant, cascade optical parametric oscillator with intracavity pumping of BaGa₂GeSe₆ in the second stage and spectral narrowing realized by a Volume Bragg Grating acting on the signal wave of the first stage which serves as a pump for the second stage. The maximum energy achieved near 8 µm in the narrowband regime is 1.1 mJ at 100 Hz (spectral width: ∼20 cm^-1, pulse duration: ∼7 ns). The overall conversion efficiency from 1 to 8 µm for broadband and narrowband operation is 4.0% and 3.1%, respectively, corresponding to quantum efficiencies of 31% and 23%.

We demonstrate a continuously tunable mid-infrared source that produces narrowband radiation at 1981 nm and 2145 nm based on a tunable Yb-based hybrid MOPA pump and a backward-wave optical parametric oscillator (BWOPO). The BWOPO employs a PPRKTP crystal with 580 nm domain periodicity. The BWOPO has a record-low oscillation threshold of 19.2 MW/cm2 and generates mJ level output with an overall efficiency exceeding 70%, reaching an average power of 5.65W at the repetition rate of 5 kHz. The system is mechanically robust and optical cavity-free, making it suitable for spectroscopic systems on mobile platforms. The mid-infrared signal frequency is tuned by pump tuning with a linear pump-to-signal frequency translation rate close to the predicted 1 to 1.001 Hz/Hz.

We demonstrate first-order quasi-phase-matched backward second-harmonic generation (BSHG) with an efficiency of 18.7%. This represents an increase by two orders of magnitude from earlier experiments employing higher-order quasi-phase-matching. The efficient BSHG is demonstrated in bulk periodically poled Rb:KTiOPO₄ with a poling period of 317 nm. Using these structures, the frequency doubling in the backward direction is achieved for the fundamental wavelength of 2309 nm. Here we report on the experimental investigation of the BSHG properties such as spectral bandwidth, temperature tuning, and temperature bandwidth by employing broadband and narrowband fundamental wavelength sources. The BSHG properties are compared with those of co-propagating second harmonic generation to reveal the BSHG potential for novel applications that were proposed theoretically but have not been realized in practice so far.

A stable, narrow-bandwidth (274 MHz) backward wave optical parametric oscillator (BWOPO) generating mJ-level backward signal at 1885nm and forward idler at 2495 nm is presented. The BWOPO was pumped by a single-longitudinal mode, Q-switched Nd:YAG high-energy laser at 1064 nm. We show that multi-transversal mode pumping leads to the spectral broadening of the BWOPO backward signal and the generation of nanosecond pulses 2.7 times above the Fourier transform limit. We demonstrate over 100 GHz continuous tuning of the parametric output by adjusting the temperature of the BWOPO crystal, showcasing the significant role of thermal expansion in tuning performance. The BWOPO signal was used as a seed for a single-stage PPRKTP optical parametric amplifier (OPA) to boost the narrowband signal and idler energies to 20 mJ. This combination of mJ-level BWOPO seed with a single-stage PPRKTP OPA comprises a simple concept that would benefit long-range differential absorption lidar (DIAL) in the near and mid-infrared regions.

The waveguiding properties of high-resistivity float zone silicon slab waveguides are characterized over the spectral range from 0.5 to 7.5 THz. Waveguide modes and dispersion are observed for lengths of 1.2 cm and silicon thicknesses from 40 to 300 µm. The influence of core thickness and cladding glass attenuation is characterized, and modeled transmitted pulse shapes compare well to the measured signals. Fused silica cladding allows propagation in the 40 µm thick wafer, demonstrating the feasibility of developing flexible semiconductor core fibers for THz transmission.