Ultra-broad gain quantum cascade lasers tunable from 6.5 to 10.4 µm.

We present a quantum cascade laser structure with an ultra-broad gain profile that covers the wavelength range from 6.5 to 10.4 µm. In a grating-tuned external cavity, we demonstrated continuous tuning from 1027 cm(-1) to 1492 cm(-1) with this broad gain laser chip. We also fabricated distributed feedback quantum cascade laser arrays with this active region design and varied grating periods. We demonstrated single wavelength lasing from 962 (10.4) to 1542 cm(-1) (6.5 µm). The frequency coverage (580 cm(-1)) is about 46% of center frequency.