We report on the first steps of maturation towards space of a nested cavity optical parametric oscillator and amplifiers, based On periodically poled nonlinear materials, emitting in the 2 mu m range for multi species differential absorption lidar (DIAL)

We have designed and built a wavelength-tunable optical source for standoff detection of gaseous chemicals by differential absorption spectrometry in the long-wave infrared. It is based on a nanosecond 2 mu m single-frequency optical parametric oscillator, whose idler wave is amplified in large aperture Rb:PPKTP crystals. The signal and idler waves are mixed in ZnGeP2 crystals to produce single-frequency tunable radiation in the 7.5-10.5 mu n range. The source was integrated into a direct detection lidar to measure sarin and sulfur mustard inside a dosed chamber, in an integrated path configuration with a noncooperative target.

Mirrorless optical parametric oscillators (MOPO) represent a special class of parametric devices based on three-wave nonlinear interaction in which the generated photons counter-propagate. Owing to the phase-matching condition of the counter-propagating waves, MOPOs can sustain oscillation without mirrors and present unique and useful tuning and spectral properties. In this paper, we will review our recent advances in structuring technology to achieve quasi-phase matching periodicities as short as 500 nm in Rb-doped KTiOPO4, which are necessary to compensate for the large phase mismatch. We will also review the performance of MOPOs both in the ps- and ns- pumping regime. In the latter, our crystals reach single-pass conversion efficiencies exceeding 50%, with mJ-level output energies.

We report on the first single-frequency parametric source tunable in the longwave infrared with an output energy of 1 mJ. The source is then used in a lidar to detect chemicals in the vapor phase.

Backward-wave OPO with forward mid-infrared idler and backward signal generation is demonstrated in 500-nm-periodicity PPRKTP. The output energy of 2.39mJ and efficiency of 46.4% is obtained. This design has potential for broad tunability in mid-infrared.

Backward-wave OPO with forward mid-infrared idler and backward signal generation is demonstrated in 500-nm-periodicity PPRKTP. The output energy of 2.39mJ and efficiency of 46.4% is obtained. This design has potential for broad tunability in mid-infrared.

High-energy, narrowband, nanosecond pulsed mid-infrared sources centred on 2 μm are requiredin applications in remote sensing, standoff detection and pollution monitoring using LIDARs.Currently, space-borne LIDAR missions are under development by major space agencies aroundthe world for active measurements of the atmospheric gas constituents and their dynamics. Thespectral range around 2 μm is one of the windows of operation for these instruments. Opticalparametric oscillators (OPOs) and amplifiers (OPAs) operating at 2 μm are often used as pumpsources for cascaded down-conversion schemes to enable generation of wavelengths deeper intothe mid-infrared. In order to fulfil these purposes, they are required to have high-energy outputwith good overall efficiency, while maintaining a narrowband or tailored spectrum. Moreover, forspace-based instruments, the radiation hardness of the parametric sources needs to be assessed.The central objectives of this thesis were the scaling of the energy and efficiency of 2 μm basedOPOs and OPAs, tailoring their spectral brightness and assessing their suitability for applicationsin space-borne active gas detection systems. Specifically, we investigated OPOs and OPAs basedon periodically-poled Rb:KTiOPO4 (PPRKTP), an engineered nonlinear material which can befabricated with large optical apertures and sub-μm periodicities. One of the key limitations toenergy scaling of these devices is the laser-induced damage threshold (LIDT) of the nonlinearmaterial used. In down-conversion schemes, the devices are subject to both high intensity 1 μmand 2 μm radiation. Prior to the work in this thesis, no LIDT value at 2 μm of KTP and Rb:KTPhad been reported. Furthermore, the work in this thesis provides data on effects of different dosageof gamma radiation on the optical properties of this material and the ways to mitigate the damageinduced by the ionizing radiation. To demonstrate energy scaling with narrow bandwidth andtunability, a nanosecond, master oscillator power amplifier (MOPA) system operating around 2μm and based on large-aperture PPRKTP was built. The MOPA system demonstrated dualnarrowband spectrum, tunable over 1.5 THz by means of a transversally chirped volume Bragggrating, while delivering tens of mJ in output. The output from this MOPA system will be furtherused for tunable THz generation. Even narrower spectra can be generated employing backwardwaveoptical parametric oscillators (BWOPO) based on PPRKTP with the periodicity of 509 nm.This work demonstrates for the first time an efficient, millijoule-level BWOPO with backwardpropagating signal. The device possessed narrowband spectrum with stable output, making it anexcellent seed source in MOPA arrangements.

We present a highly-reliable fabrication technique for sub-µm PPRKTP demonstrating periodicities as short as 500 nm. The crystals are used for counter-propagating three-wave mixing interactions with a conversion efficiency exceeding 50% and mJ-level output energy.

We report on a longwave infrared lidar, tailored for detection of chemical warfare agents in the gaseous phase. The emitter is based on single-frequency 2 μm parametric oscillator/amplifier systems followed by a ZnGeP2 downconversion stage.

We report on a longwave infrared lidar, tailored for detection of chemical warfare agents in the gaseous phase. The emitter is based on single-frequency 2 μm parametric oscillator/amplifier systems followed by a ZnGeP2 downconversion stage.