Tunable phase-mismatched mid-infrared difference-frequency generation between 6 and 17 µm in CdTe.

In parametric conversion, phase-matching techniques such as birefringence and quasi phase-matching (PM) with the designed crystal angle or periodically poled polarities are employed to fulfill the requirement of momentum conservation. However, directly using phase-mismatched interactions in nonlinear media with large quadratic nonlinear coefficient remains unheeded. Here, for the first time to the best of our knowledge, we study the phase-mismatched difference-frequency generation (DFG) in an isotropic cadmium telluride (CdTe) crystal, with the comparison of other DFG processes based on birefringence-PM, quasi-PM, and random-quasi-PM.

Ultrabroad (3.7-17 µm) tunable femtosecond optical parametric amplifier based on BaGaSe crystal.

We demonstrate the first (to the best of our knowledge) tunable femtosecond (fs) mid-infrared (MIR) optical parametric amplifier (OPA) based on BaGaSe (BGSe) crystal with an ultra-broadband spectral range. Benefiting from the broad transparency range, high nonlinearity, and relatively large bandgap of BGSe, the MIR OPA pumped at 1030 nm with a repetition of 50 kHz has an output spectrum that is tunable across an extremely wide spectral range spanning from 3.7 to 17 µm.