A multiwavelength semiconductor laser

Many systems, such as atoms and molecules in gas mixtures, dye solutions and some solid-state materials, can exhibit simultaneous laser action at several wavelengths as a result of the excitation of several optical transitions 1 . But semiconductor lasers are usually monochromatic because the electronic levels are distributed in continuous energy bands 2 . In order to achieve simultaneous lasing at several well-separated wavelengths, researchers have proposed 3 combining different semiconductors with distinct bandgap energies in the active material. However, the difficulty of pumping different regions and of absorption of the shorter-wavelength light could be resolved only by using separated multiple resonators or by multisection injection devices 4 , 5 , 6 , 7 . Here we report the realization of a single artificial semiconductor material with distinct optical transitions, which permits simultaneous multiwavelength laser action at mid-infrared wavelengths (6.6, 7.3 and 7.9 µm). This is achieved by tailoring the electronic states and electron relaxation times in the material, which is a superlattice layered structure. The laser has potential applications in sensors for trace-gas analysis.