HIGH-PERFORMANCE UNCOOLED 1.3-MU-M ALXGAYIN1-X-YAS INP STRAINED-LAYERQUANTUM-WELL LASERS FOR SUBSCRIBER LOOP APPLICATIONS/

Design considerations for fabricating highly efficient uncooled semico nductor lasers are discussed. The parameters investigated include the temperature characteristics of threshold current, quantum efficiency, and modulation speed. To prevent carrier overflow under high-temperatu re operation, the electron confinement energy is increased by using th e AlxGayIn1-x-y As/InP material system instead of the conventional Gax In1-xAsyP1-y/InP material system. To reduce the transparency current a nd the carrier-density-dependent loss due to the intervalence-band abs orption, strained-layer quantum wells are chosen as the active layer. Experimentally, 1.3-mum compressive-strained five-quantum-well lasers and tensile-strained three-quantum-well lasers were fabricated using a 3-mum wide ridge-waveguide laser structure. For both types of lasers, the intrinsic material parameters are found to be similar in magnitud e and in temperature dependence if they are normalized to each well. S pecifically, the compressive-strained five-quantum-well lasers show ex cellent extrinsic temperature characteristics, such as small drop of 0 .3 dB in differential quantum efficiency when the heat sink temperatur e changes from 25 to 100-degrees-C, and a large small-signal modulatio n bandwidth of 8.6 GHz at 85-degrees-C. The maximum 3 dB modulation ba ndwidth was measured to be 19.6 GHz for compressive-strained lasers an d 17 GHz for tensile-strained lasers by an optical modulation techniqu e. The strong carrier confinement also results in a small k-factor (0. 25 ns) which indicates the potential for high-speed modulation up to 3 5 GHz. In spite of the aluminum-containing active layer, no catastroph ic optical damage was observed at room temperature up to 218 mW for co mpressive-strained five-quantum-well lasers and 103 mW for tensile-str ained three-quantum-well lasers. For operating the compressive-straine d five-quantum-well lasers at 85-degrees-C with more than 5 mW output power, a mean-time-to-failure (MTTF) of 9.4 years is projected from a preliminary life test. These lasers are highly attractive for uncooled , potentially low-cost applications in the subscriber loop.