Room temperature, continuous wave (CW) operation of distributed feedback (DFB) quantum cascade lasers with widely
spaced operation frequencies is reported. The relatively small temperature tuning range of a single device, smaller or
equal to approximately 1 % of the wavelength, usually limits their efficiency for spectroscopic investigations. By using a
bound-to-continuum active region to create a broad gain spectrum and monolithic integration of different DFB gratings,
we achieved high-performance devices with single-mode emission between 7.7 and 8.3 &mgr;m at a temperature of +30 °C.
This frequency span corresponds to 8 % of the center frequency. The maximum CW operation temperature achieved was
63 °C at the gain center and as much as 35 °C and 45 °C, respectively, at the limits of the explored wavelength range.