Continuous-wave operation of a broadly tunable thermoelectrically cooled external cavity quantum-cascade laser

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??m. 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 4.94to5.4??m and was single mode over more than 140?cm?1. The output power was in excess of 10?mW over ?100?cm?1 and in excess of 5?mW over ?130?cm?1 at ?30°C.