Narrow-linewidth fast-tunable external-cavity near-infrared diode lasers for trace gas detection

Summary form only given. DFB and DBR diode lasers in the near infrared (800-1650 nm) are well suited for atmospheric absorption measurements and trace gas detection. These lasers are single frequency and continuously tunable by temperature or laser current. The advantageous properties of these diode lasers can be improved considerably by simple external-cavity configurations. In our investigations an aspheric lens and a plane mirror with a reflectivity of 20-50% at a distance of about 20 mm of the laser facet was used as an additional resonator. This resonator significantly narrows the spectral linewidth, and reduces the intensity of the side modes, as well as the amplitude noise.