Optimization of broadband quantum cascade lasers for continuous wave operation

We have optimized the design of the broadband quantum cascade laser for cw operation. The improved design leads to a gain ripple of only about 4 cm−1 over more than a 0.5-μm spectral range. Simultaneous cw emission at several wavelengths spanning the range between 6.7 and 7.4 μm has been achieved in a temperature interval from 20 to 77 K.