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-mum spectral range. Simultaneous cw emission at several wavelengths spanning the range between 6.7 and 7.4 mum has been achieved in a temperature interval from 20 to 77 K. (C) 2003 American Institute of Physics.