External cavity quantum-cascade laser tunable from 8.2 to 10.4 μm using a gain element with a heterogeneous cascade

A heterogeneous quantum-cascade structure based on two bound-to-continuum designs emitting at 9.6 and 8.4 mu m is presented. Its spontaneous emission spectrum at room temperature has a full width at half maximum of 350 cm(-1) and shows a variation of intensity of less than 20% over more than 200 cm(-1). External cavity lasers using a grating in Littrow configuration and antireflection coated chips with this active region could be tuned over 265 cm(-1) from 8.2 to 10.4 mu m, that is, over 24% of the center wavelength. (c) 2006 American Institute of Physics.