A highly efficient room-temperature nanolaser

Has been demonstrated by scientists at Yokohama National University in Japan. Made of the semiconductor gallium indium arsenide phosphate, the overall device has a width of several microns, but the active region where laser light actually gets produced has nanometer-scale dimensions in all directions. The device is the first nanolaser to emit continuous coherent near-IR light at room temperature and uses only a microwatt of power, one of the smallest operating powers ever achieved. The laser’s small size and high efficiency were made possible by its photonic-crystal design. The researchers etched a repeating pattern of holes through the semiconductor and deliberately introduced a defect into the pattern—for example, by slightly shifting the positions of two holes, as shown here. The imperfect pattern defined a narrow frequency band of light that could exist in the defect region. Curiously, the team found that a high quality factor Q was not necessarily advantageous for optimized device behavior. A high Q may be desirable for low-threshold lasing, but a low Q should be more effective in such applications as a single-photon emitter. (K. Nozaki, S. Kita, T. Baba, Opt. Express 15 , 7506, 2007 http://dx.doi.org/10.1364/OE.15.007506 .)