External-cavity tunable diode lasers (TDLs) can provide access to the visible and near-infrared regions of the electromagnetic spectrum, at wavelengths between approximately 350 nm and 3 microns. The wavelength and power output of TDLs are controlled by current and temperature controllers and also by adjustment of the external cavity (most commonly a reflective diffraction grating). In our laboratory, TDLs have been used to measure H2O concentrations. TDLs can be operated in fixed- or scanned-wavelength configurations and are arranged in the same general direct absorption setup as for QCLs.
General schematic of a grating-stabilized TDL.
TDL setup at the Petersen Research group to measure H2O.