Abstract

Mid-infrared laser absorption spectroscopy is a promising technique for environmental trace-gas detection because many important air contaminants have strong absorption bands in that spectral region. To access the 3-5 μm spectral region a convenient technique is difference frequency mixing in a nonlinear material, which allows the frequency shifting of readily available near infrared diode laser sources. Periodically poled LiNbO, (PPLN) has desirable characteristics for such difference frequency mixing, including engi-neerable phase matching and a high non-linear coefficient (d_eff). The use of a tapered waveguide written onto the PPLN, leads to a further enhancement of the conversion efficiency of PPLN.^1,2

© 1999 Optical Society of America