InAs/AlSb widely tunable external cavity quantum cascade laser around 3.2 µm

Room temperature, tunable, external-cavity short-wavelength InAs/AlSb quantum cascade laser (QCL) is reported. Wavelength tuning of 85nm for the spectral range between 3190 nm and 3275nm has been achieved by rotating the diffraction grating forming the external cavity. To suppress lasing inside the QCL cavity, its ridge was tilted by 7 at the external cavity end. The optimal tilting angle of the laser ridge was chosen by careful consideration of the return losses of the TM-polarized waveguide mode from the diffraction grating in a quasi-Littrow configuration and the Fabry-Perot feedback from the tilted laser facet. No antireflection coating was used.