Intersubband absorption of quantum cascade laser structures and its application to laser modulation

We have analyzed light absorption in a quantum cascade laser (QCL) structure under forward and reverse bias. Strong laser frequency absorption modulation is predicted and observed for the voltage variation within the high differential resistance voltage range. We propose to use this mechanism for monolithically integrated intracavity modulation of QCLs with suppressed thermal chirp. In addition, the described method allows for extraction of the intersubband absorption component of the total waveguide losses. (C) 2008 American Institute of Physics.