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Coherent MIR radiation has several applications such as remote sensing, laser surgery, nonlinear spectroscopy, countermeasures, etc. Generation of coherent MIR radiation is achieved by solid state laser and quantum cascade laser with direct MIR lasing, or nonlinear frequency conversion from laser with shorter wavelength. In this thesis, we developed several different laser configurations to access the MIR wavelengths. Firstly, a high repetition rate high power Ho:YAG laser was developed to generate high average power MIR ns pulse in an intra-cavity ZGP OPO configuration. A high energy Ho:YAG MOPA laser pumped ZGP crystal in an extra-cavity OPO configuration was demonstrated. A novel uncoated wedge ZGP OPO configuration was studied, addressing the AR-coating limitation encountered in conventional ZGP OPO. Secondly, Coherent Polarization Locking configuration was implemented in Ho:YAG oscillator. Studies show the Coherent Polarization Locking configuration improves the beam quality in CW operation and reduces the risk of intra-cavity optical damage in pulse operation. Improvement in beam quality is due to the reduction of thermal related effects in the oscillator. Splitting the intra-cavity intensity in the Coherent Polarization Locking cavity reduces the possibility of intra-cavity optical damage. Lastly, a high energy Yb:CaF2 regenerative amplifier was developed as the pump source for a multi-stage ZGP OPA setup to generate fs MIR laser pulses. To increase the efficiency of fs MIR generation, a high energy Ho:YAG regenerative amplifier was explored as the direct pump source for ZGP OPA system. DOCTOR OF PHILOSOPHY (SPMS)

Ultrafast laser sources operating in the mid-infrared spectral region, where many molecules and their functional groups have vibrational and rotational resonances, are very important tools for studying novel regimes of non-linear optics and strong field physics. Next to optical parametric amplifiers (OPAs) based on ZnGeP 2 (ZGP) crystals which, on the one hand, allow generation of energetic ultrashort mid-IR pulses at a mJ energy level, but, on the other, rely on complex and immature holmium pump lasers [1], a difference frequency generation (DFG) in AGS or GaSe crystals starting from a single broadband near-infrared (NIR) pulse [2] or via cascaded two-stage parametric down-conversion [3] is an alternative way to generate mid-IR pulses above 4-μm wavelength. In the later case more conventional Ytterbium, Neodymium or Ti:Saphire lasers are used to pump the frequency conversion stages. The use of a longer-wavelength 1.03 μm Ytterbium laser as compared to Ti:Sapphire pump sources yields an improved phase matching bandwidth, lower group velocity miss-match, as well as a lack of three-photon absorption, which reduces detrimental photo-darkening in AGS.

We demonstrate an efficient difference frequency generation in the 5-11 μm spectral range. A KTA-AGS based parametric source is driven by 14 mJ Yb:CPA and provides 150 μJ pulses with up to 3 μm bandwidth.

We demonstrate efficient difference frequency generation in the 5–11 µm range using AGS crystal pumped at wavelengths beyond two-photon absorption limit. A simple and efficient 15 mJ Yb-based driver and a cascaded KTA/AGS parametric down-conversion allow generation of 150 µJ pulses with bandwidth spanning 7–10 µm.

Gigawatt-peak-power radiation, tunable in the 5-9 µm spectral window is generated as a difference frequency between the signal and idler pulses, originating from a KTA optical parametric amplifier pumped by 100-mJ, 200-fs Yb laser.