No abstract

Continuous-wave operation of an external cavity quantum-cascade laser on a thermoelectric cooler is reported. The active region of the gain element was based on a bound-to-continuum design emitting near 5.15 microm. The external cavity setup was arranged in a Littrow configuration. The front facet of the gain chip was antireflection coated. The laser could be tuned over more than 170 cm(-1) from 4.94 to 5.4 microm and was single mode over more than 140 cm(-1). The output power was in excess of 10 mW over approximately 100 cm(-1) and in excess of 5 mW over approximately 130 cm(-1) at -30 degrees C.

External cavity quantum-cascade lasers (QCLs) emitting in the long-wave infrared (LWIR) around 10 µm and in the mid-wave infrared (MWIR) around 5.2 µm have been realized. The coupling facet of the QC chips was anti-reflection coated and the optical feedback was provided by a diffraction grating arranged in a Littrow configuration. The active regions of the gain elements were based on bound-to-continuum designs having broad gain curves ( ∼ = 300 cm −1 full width at half maximum). The LWIR laser was operated in pulsed mode on a thermoelectric (TE) cooler. It could be tuned over a frequency range of 150 cm −1 from 9.1 to 10.55 µm with a peak power ≥ 30 mW. The MWIR laser was operated in continuous-wave (CW) mode on a TE cooler. It could be tuned over more than 170 cm −1 from 4.95 to 5.4 µm and was single-mode over more than 140 cm −1 . Its output power was in excess of 5 mW over 130 cm −1 . This broad tunability (10 times more than that of distributed-feedback QCLs) enables new applications of QCLs in high-resolution infrared spectroscopy.