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...

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