CW operation of 1.55-μm bipolar cascade laser with record differential efficiency, low threshold, and 50-/spl Omega/ matching

By electrically segmenting an InP ridge laser and series-connecting the segments, we have created the first highly scalable bipolar cascade lasers. We report room-temperature continuous-wave operation of 12-stage lasers with a record 390% differential efficiency and 2.8-mA threshold, as well as three-stage lasers with 50-/spl Omega/ input impedance and 118% efficiency.