Abstract

Mid-infrared (IR) light sources are attracting increasing interest for use in trace gas sensing. In particular, wavelength conversion techniques such as the optical parametric oscillator (OPO) approach and difference frequency generation (DFG) are promising since they can generate a continuous wave (CW) output at room temperature in the 3-5 μm range where various enviromnental gases exhibit strong absorption lines. High power OPO using a bulk quasi-phase matched (QPM) LiNbO₃ crystal [1] can achieve an agile scan only over a limited wavelength range due to mode hopping. In contrast, single pass DFG in a high-efficiency QPM LiNbO₃ waveguide [2] provides the potential for compact and robust mid-IR sources with a wider continuous tuning range. For such applications as open path remote sensing and gas sensing using a cavity cell, a high-power (tens of mW) mid-IR source is essential. The most significant concern in this respect is photorefractive damage in the waveguide. Here, we report high-power 3.4-μm DFG in a damage resistant Zn:LiNbO₃ waveguide fabricated with direct bonding technology. Using a CW high-power fiber amplifier (FA) as the pump source, we obtained a mid-IR output of as high as 65 mW, which is the highest mid-IR output from a waveguide device yet reported.

© 2007 IEEE