Optically and electrically pumped grating-coupled external cavity quantum cascade laser

An optically and electrically pumped external cavity (EC) quantum cascade laser (QCL) is reported. A Fabry-Perot (FP) QCL with no anti-reflective facet coating is utilized as the gain chip in a Littrow configuration. A distributed feedback (DFB) QCL is used to optically pump the FP QCL, in addition to electrical pumping. The developed setup has three advantages: the threshold current and compliance voltage of the FP QCL decreases further, the optical power of the EC QCL increases significantly in the spectral range of the pumping laser (similar to 20 dBm), and a double-mode operation is achieved. A widely course doublemode tuning range of 350 nm for the spectral range between 4450 and 4800 nm in pulsed operation is achieved. To the best of our knowledge, it is the first demonstration of such an EC QCL.