A tunable mid-infrared continuous-wave (cw) spectroscopic source in the 3.4-4.5 micrometers region is reported, based on difference frequency generation (DFG) in a quasi-phase-matched periodically poled RbTiOAsO4 (PPRTA) crystal. DFG power levels of 10 microW were generated at approximately 4 micrometers in a 20-mm long PPRTA crystal by mixing two cw single-frequency Ti:Al2O3 lasers operating near 713 nm and 871 nm, respectively, using a laser pump power of 300 mW. A quasi-phase-matched infrared wavelength-tuning bandwidth (FWHM) of ~ 12 cm-1 and a temperature tuning rate of 1.02 cm-1/degree C were achieved. Experimental details regarding the feasibility of trace gas detection based on absorption spectroscopy of CO2 in ambient air using this DFG radiation source are also described.
The first demonstration, to the best of our knowledge, of continuous-wave (cw) difference-frequency generation in LiInSz crystal is reported. Two Art laser-pumped Ti:Sapphire lasers were employed as widely tunable pump sources. A LiInSl crystal (5 mm x 5 mm x 10 mm) cut at Q = 42" and 8 = 90° was used as frequency downconverter. Wide spectral coverage (5.5-1 1.2 pm), extending beyond the 50% IR-cutoff wavelength of 8.5 microns, has been obtained with angle and wavelengths tuning under type I1 (eoe) critically phase-matched parametric interaction. The phase-matching (PM) conditions in the cw DFG process have been investigated, which allow to improve the Sellmeier parameters by use of the experimental PM data with a'two-pole Sellmeier model. With a total input power intensity of -5 kW/cmz, DFG power of 33.5 nW was produced at 7 pm, which yielded a power conversion efficiency of about 1 pW/(W2.cm), and an estimated effective nonlinear coefficient d,ff of 4.17 p d V .
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.