Abstract

Continuous-wave (cw) laser sources offering practical powers in the mid-infrared (mid-IR), in particular the 6–8 μm spectral range, are of great interest for a variety of medical and biological applications. Nonlinear optical techniques based on difference-frequency generation (DFG) and optical parametric oscillators (OPOs) represent an effective approach for deep mid-IR generation. Orientation-patterned (OP)-GaAs is a highly attractive nonlinear crystal for this purpose, due to its high nonlinear coefficient (d_eff=d₁₄∼94 pm/V), wide transparency across 0.9-17 μm, high thermal conductivity (46 W/mK), and high damage threshold [1]. In the past few years, DFG based on OP-GaAs, with cw output powers up to sub-mW has been demonstrated in the deep mid-IR [2]. However, the attainment of high output power leading to noise-free and pure spectral output has remained highly challenging. Here, we report the generation of multi-tens of mW level output power in the 6.4-7.5 μm spectral range by exploiting DFG between a high-power Yb-fiber-pumped cw OPO and a cw Tm-fiber laser in OP-GaAs [3]. To our knowledge, this is the highest cw power together with wide tunability achieved in the deep mid-IR.

© 2015 IEEE