U.S. scientists say they have achieved a breakthrough in quantum cascade laser output power, delivering 120 watts from a single device at room temperature. The Northwestern University researchers, led by Professor Manijeh Razeghi, said their accomplishment is particularly attractive for infrared countermeasures -- a way of misguiding incoming missiles to protect commercial and military aircraft. Unlike conventional interband semiconductor lasers, the scientists said their quantum cascade laser is an intersubband device requiring only electrons to operate. Razeghi's team demonstrated the ridge width of a broad-area quantum cascade laser can be increased up to 400 microns, without suffering from filiamentation --...