We report the first optically pumped mode-locked semiconductor laser operating at wavelengths longer than 1.0 µm. Laser operation has been achieved in two separate compositions of In1−x GaxAsyP1−y at 1.1 and 1.2 µm with x = 0.20, y = 0.4 and x = 0.24, y = 0.55, respectively. Continuous wave operation was obtained with more heating problems than were observed in CdS1 and CdSSe2 due to relatively poor thermal conductivity in the quaternary layer. To reduce this effect during pulse width and spectral measurements, the pump beam was mechanically chopped.
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