Packing techniques to increase wavelength tuning of distributed feedback lasers

Summary form only given. Distributed feedback (DFB) diode lasers are used as sources in laser absorption spectrometers for trace gas analysis. Many molecules, including common environmental pollutants and toxic chemicals, have absorption bands between 760 nm and 2004 nm. These bands are strong enough to allow detection at or below the parts-per-million (ppm) level. In order to sweep through an absorption peak a wavelength tuning range of over one wave number is typically required. In FM spectroscopy the wavelength of the laser is tuned with temperature close to the absorption peak. A low-frequency (ranging from a few Hz to 1 kHz) saw tooth current ramp is then applied to the diode laser that repetitively sweeps its emission frequency across the absorption peak. One needs as high as possible a current tuning rate for as small as possible a current change to minimize power changes and non-linearity.