In this work, a novel 2.7 µm source used for CO2 and H2O vapor spectroscopy using the backward propagating wave of a backward wave optical parametric oscillator (BWOPO) is demonstrated for the first time to our knowledge. The unique properties of BWOPOs eliminate the need for additional spectral narrowing or wavelength stabilization, enabling the use of a multi-longitudinal mode Q-switched pump laser centered around 1030 nm. A full characterization of the source is presented, revealing a central output at 2712 nm, showcasing a temperature tuning of −1.77 GHz/K, and achieving an output pulse energy of 2.3 µJ. Novel methods are introduced for measuring the linewidth and wavelength stability using the ambient laboratory air. These approaches demonstrate a narrow output of 43 pm and establish an upper limit of stability at 65 MHz, with no active means of stabilization. These findings underscore the potential of BWOPOs as a robust platform for future differential absorption lidar (DIAL) systems.

We present backward wave optical parametric oscillator waveguides implemented in periodically poled Rb-doped KTP. The waveguides demonstrated low loss (0.16 dB/cm) and exhibited an oscillation threshold 19 times lower than the corresponding bulk device.

We present backward wave optical parametric oscillator waveguides implemented in periodically poled Rb-doped KTP. The waveguides demonstrated low loss (0.16 dB/cm) and exhibited an oscillation threshold 19 times lower than the corresponding bulk device.

The first demonstration of a 2.7 µm CO2 gas sensing source exploiting a backward wave optical parametric oscillator (BWOPO). Transmission measurements of the backward wave are demonstrated through air with good agreement with simulations.

Backwards Wave Optical Parametric Oscillators (BWOPOs) eliminate the need for a resonant cavity, offering a compact and robust alternative to traditional OPOs. In this study, a BWOPO using a PPKTP crystal with a 765 nm poling period was pumped by a Q-switched laser at 1030 nm, delivering 40 μJ pulses. The backward wave generated at 2.8 μm exhibited a narrow spectral bandwidth of 1.75 GHz, despite the pump's broad 360 GHz bandwidth. The extracted pulse energy was around 5 μJ. These results highlight the BWOPO's potential for applications requiring precise wavelength control and stability.

For the first time, we show spectral and polarization indistinguishability of photon pairs generated in counter-propagating degenerate spontaneous parametric downconversion in the telecommunications band using first-order quasi-phase-matching in periodically poled Rb-KTiOPO4.

For the first time, we show spectral and polarization indistinguishability of photon pairs generated in counter-propagating degenerate spontaneous parametric downconversion in the telecommunications band using first-order quasi-phase-matching in periodically poled Rb-KTiOPO4.

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 mag-nitude 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 band-width, temperature tuning, and temperature bandwidth by employing broadband and narrowband fundamental wave-length 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.

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.