A diode-pumped Nd:YAG laser is passively Q switched by using F(2)(-) color centers in lithium fluoride as a saturable absorber. When cw pumped with a laser diode, the laser produces pulses of 20-30-nsec duration at 1064 nm, with an energy of as much as 20 microJ and a peak power of more than 1 kW. Data are presented on pulse width, energy, and repetition rate as a function of pump power. When the laser is operated at high pulse energy levels, a gradual bleaching of the saturable absorber is observed.

3 W cw output power has been obtained from aluminum-free, strained-layer double-quantum well ͑DQW͒ InGaAs/InGaAsP/InGaP uncoated, 100-m-wide stripe diode lasers ͑ϭ0.945 m͒ grown by low-pressure MOCVD on exact ͑100͒ GaAs substrates. The combination of high-band-gap ͑1.62 eV͒ InGaAsP confinement layers and the DQW structure provides relatively weak temperature dependence for both the threshold current I th as well as the external differential quantum efficiency d . Furthermore, the series electrical resistance for 100 mϫ600 m stripe-contact devices is as low as 0.12 ⍀. As a result, the power conversion efficiency reaches a maximum of 40% at 8 ϫI th , and decreases to only 33% at the maximum power ͑i.e., 3 W͒ at 28ϫI th . Low-temperature ͑12 K͒ photoluminescence measurements of InGaAs/InGaAsP quantum-well structures exhibit narrow linewidths ͑Ͻ10 meV͒ for material grown on exact ͑100͒ GaAs substrates, while growths on misoriented substrates exhibit linewidth broadening, as a result of ''step bunching.'' Laser structures grown on misoriented substrates exhibit increased temperature sensitivity of both I th and d , compared with structures grown on exact ͑100͒ substrates. © 1995 American Institute of Physics.Strained-layer quantum-well InGaAs lasers ͑980 nm͒ are needed as high-output-power pump sources for Er-doped fiber and waveguide amplifiers as well as for fluoride-fiberbased frequency upconversion. The use of the aluminum-free InGaAs/InGaAsP/InGaP material system has several advantages over the InGaAs/GaAs/AlGaAs material system for the realization of reliable, high-power diode sources: ͑1͒ the low reactivity of InGaP to oxygen facilitates regrowth for the fabrication of single-mode index-guided structures, 1,2 ͑2͒ higher electrical and thermal conductivity compared with AlGaAs, 3 and ͑3͒ lasers with AlGaAs cladding layers and unpassivated facets show higher facet degradation than similar lasers with InGaP cladding layers, 4 presumably due to the lower surface recombination velocity of InGaP 5 compared with AlGaAs. Al-free lasers also exhibit an order of magnitude lower facet temperature rise compared with devices containing AlGaAs in both the confining and cladding layers. 6 Although high performance has been demonstrated from Al-free laser structures, the characterization of the quantum-well growth for this material system and its influence on device performance have not been established.Achieving high cw output power requires weak temperature dependence of both the threshold current, I th , and differential quantum efficiency, d which in turn are influenced by carrier leakage from the quantum well͑s͒. Al-free lasers with GaAs or low-band-gap InGaAsP confinement layers exhibit strong carrier leakage from the InGaAs quantum well to the ͑optical͒ confinement layers, resulting in a strong temperature dependence of both I th and d . [7][8][9] To circumvent this problem, the use of higher band-gap InGaAsP confinement layers and multiple quantum wells have been used to reduce carrier leakage, and thereby reduce temp...

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