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 transitions1. But semiconductor lasers are usually monochromatic because the electronic levels are distributed in continuous energy bands2. In order to achieve simultaneous lasing at several well-separated wavelengths, researchers have proposed3 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 devices4,5,6,7. 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.