Abstract

Coherent mid-IR sources (2.5 – 4 μm) combining high average power and high pulse energy are essential for a great number of industrial, scientific and commercial applications. Furthermore, they have broad medical implications, due to the high water absorption around 3μm. Due to the limited choice of laser materials emitting directly in this spectral range, covering it can be efficiently achieved through nonlinear frequency conversion devices, pumped by Q-switched Nd-laser systems, operating at kHz repetition rates. A fundamental efficiency limitation in short-pulsed OPOs is the available resonant wave build-up time. In order to keep this time period small compared to the pump pulse duration in short cavity OPOs, one should make use of highly nonlinear optical media. Furthermore, pulsed OPOs reaching mJ level output are prone to optical component damage due to the high amount of energy circulating inside the OPO cavity [1]. Mid-IR OPO output can be scaled significantly beyond this threshold by employing an optical parametric amplification (OPA) stage, determining the output energy and efficiency of the whole system [2]. Naturally, given the potential benefits, the search for nonlinear materials for frequency conversion in mid IR have recently intensified [1, 2]. However for really high power (energy) frequency down-conversion devices in the spectral region between 2.5 and 4 μm, periodically poled stoichiometric lithium tantalate (PPSLT) with its low coercive field (0.8 kV/mm), high refraction damage threshold and transparency up to 5 μm, is amongst the very few suitable candidate.

© 2013 IEEE