Broadband tuning of external cavity bound-to-continuum quantum-cascade lasers

A quantum-cascade structure based on a bound-to-continuum design exhibiting a broad gain curve is presented. The full width at half maximum of the measured luminescence spectrum is $\text{297\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}$ at room temperature. Grating-coupled external cavity lasers using this active region could be tuned over $\text{150\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}$ (1.45 μm), which is equal to 15% of the free running wavelength $\text{(λ≅10\hspace{0.17em}μ}\mathrm{m}\mathrm{),}$ in pulsed mode at room temperature. Time resolved spectra showed a single-mode operation with a 30 dB side mode suppression ratio after the first 12 ns of the pulse.