Parametric generation of tunable infrared radiation for remote sensing applications

Abstract

We are developing a high energy, narrow linewidth, and tunable mid-IR laser source that can be used to measure the green house gases and toxic gases with sufficient sensitivity and accuracy. This system consists of three major components; a high energy seeded 2.05-micron pump laser, a parametric oscillator and amplifier tunable between 3 to 9 microns and a continuous wave Periodically Poled Lithium Niobate (PPLN) seed source for parametric oscillator. A high-energy 2.05-micron pump laser with 600-mJ output has been demonstrated. This laser is comprised of one oscillator and two amplifiers. It is operated in a double pulse format to increase the system efficiency. The high beam quality combined with the narrow linewidth feature makes it a superior pump source for the parametric oscillator and amplifier. A seed source for the parametric oscillator can be implemented by using a PPLN continuous wave Optical Parametric Oscillator (OPO). The efficiency of this PPLN OPO can be greatly increased because of the huge nonlinearly associated with the d33 element of the nonlinear tensor of this material and the non-critical phase matching. Recent significant material growth improvement of ZnGeP2 makes it possible to produce the crystal with sufficient low absorption at the 2.05 pump wavelength (<0.1cm-1). This crystal also has the characteristics of wide transparency range and large second-order nonlinearities. Such a crystal is one of the most promising nonlinear optical materials for efficient frequency conversion into the mid-IR spectral region. In this paper, the design and preliminary results of this laser system will be presented.