HIGH-PERFORMANCE 1.5 MICRO-M WAVELENGTH INGAAS-INGAASP STRAINED QUANTUM-WELL LASERS AND AMPLIFIERS

Semiconductor lasers and laser amplifiers in the 1.48-1.55-mu-m wavelength band employing In(x)Ga1-xAs-In-GaAsP quantum wells grown under 1.2-1.8% compressive (x = 0.7 and 0.8, respectively) and 1.6% tensile (x = 0.3) strain are reported. Improved performance of compressively strained quantum well devices is observed as theoretically predicted from the strain-induced band structure modifications resulting in reduced effective hole mass and reduced magnitude of Auger Recombination and Intervalence Band Absorption. In0.7Ga0.3As-InGaAsP single quantum well lasers have lowest threshold current densities of 160 A/cm2, and In(x)Ga1-xAs four quantum well lasers show external differential efficiencies of 82%, highest T0-values of 97 K for x = 0.7 and 0.8, respectively, and record highest CW output powers of 325 mW for x = 0.7. Aging tests performed at 100 mW CW output power for 6200 h demonstrate the excellent reliability of 1.8% compressively strained In0.8Ga0.2As quantum well lasers. In0.8Ga0.2As multiple quantum well three-section distributed feedback lasers show a largest single mode tuning range of 7.2 nm with very narrow linewidth less-than-or-equal-to 1 MHz, which is virtually independent of tuning. Laser amplifiers with the same strained multiple quantum well active region show a record single pass gain as high as 31 dB and 3 dB less spontaneous emission as compared to bulk InGaAsP amplifiers. All the compressively strained quantum well devices show TE mode gain. Improved performance of 1.6% tensile strained In0.3Ga0.7As quantum well devices is reported also. These devices show TM mode gain, demonstrating the strain-induced heavy hole-light hole reversal in the valence band. Lasers employing these tensile strained quantum wells show higher and narrower gain spectra, and laser amplifiers have a higher differential gain, both compared to compressively strained quantum well devices. Consequently, the tensile strained quantum well lasers show the smallest linewidth enhancement factor alpha = 1.5 (compression alpha = 2.5) and the lowest K factor of 0.22 ns (compression K = 0.58 ns) resulting in an estimated intrinsic 3 dB modulation bandwidth of 40 GHz (compression 15 GHz). Furthermore, a record highest CW operating temperature of 140-degrees-C was observed for the tensile strained quantum well lasers. This high performance of the tensile strained quantum well devices is not predicted by theory.