Heterogeneous high-performance quantum-cascade laser sources for broad-band tuning

Abstract

A heterogeneous high-performance quantum-cascade laser gain chip comprising two bound-to-continuum active region designs emitting at 8.2 and 9.3 μm is presented. Its extrapolated gain spectrum has a full-width at half-maximum (FWHM) of 350 cm-1. Though a broad gain bandwidth invariably results in a reduced gain cross section, devices with a high-reflection coated back facet still lase continuous-wave (CW) up to a temperature of 50°C and demonstrates output powers in excess of 100 mW at 30° C. Such high performance was achieved by designing the waveguide in a buried heterostructure fashion and epi-down mounting on a diamond submount, resulting in a thermal resistance of only 4.8 K/W. In pulsed mode, we reached a peak output power of 1 W at room temperature. Finally, in order to prove the usability for broad-band tuning, this chip was antireflection coated on the front facet with a residual reflectivity of < 2.5 X 10-3 and used in our external cavity (EC) setup operated at room temperature. In pulsed mode, we were able to tune the gain chip over 292 cm-1, which is 25 % of center frequency. In CW, we reached a coarse tuning range of 201 cm-1 (18%) and an output power in excess of 135 mW at the gain maximum at 15°C. This gain chip enabled CW room temperature EC tuning with output powers in excess of 20 mW over 172 cm-1. © 2008 IEEE.