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Al-free 980 nm InGaAs/InGaAsP/InGaP laser structures grown by low-pressure metalorganic chemical vapor deposition ͑LP-MOCVD͒ have been optimized for high cw output power by incorporating a broad waveguide design. Increasing the optical-confinement layer total thickness from 0.2 to 1.0 m decreases the internal loss fivefold to 1.0-1.5 cm Ϫ1 , and doubles the transverse spot size to 0.6 m ͑full width half-maximum͒. Consequently, 4-mm long, 100-m-aperture devices emit up to 8.1 W front-facet cw power. cw power conversion efficiencies as high as 59% are obtained from 0.5-mm long devices. Catastrophic-optical-mirror-damage ͑COMD͒ power-density levels reach 15.0-15.5 MW/cm 2 , and are found similar to those for InGaAs/AlGaAs facet-coated diode lasers. © 1996 American Institute of Physics. ͓S0003-6951͑96͒01237-5͔Diode lasers with reliable operation in the 980 nm wavelength range are needed for applications such as pump sources for solid-state lasers or rare-earth-doped fiber amplifiers, and medical therapy. The growth of InGaAsP alloys lattice-matched to a GaAs substrate is very attractive as an aluminum-free alternative to the conventional AlGaAs-based materials. The aluminum-free InGaAs͑P͒/InGaP/GaAs material system has several advantages over the GaAs/AlGaAs material system for the realization of reliable, high-power diode laser 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 3,4 and thermal conductivity 5 compared with AlGaAs, ͑3͒ potential for improved reliability, 6 and ͑4͒ potential for growth of reliable diode lasers on Si substrates. 7 Here, we report on the optimization of InGaAs/InGaAsP/InGaP strained-layer quantum well laser structures by using the broad-waveguide concept, 8,9 for maximizing the cw output power. As a result, record cw performances ͑8.1 W front-facet power, cavity length Lϭ4 mm; and 59% wallplug efficiency, Lϭ0.5 mm͒ are obtained from broad-area ͑100-m wide stripe͒ devices. Catastrophic optical mirror damage ͑COMD͒ values from LR/HR facet-coated devices under cw operation ͑i.e., ϳ15 MW/cm 2 ) are found to be similar to those for InGaAs/ AlGaAs facet-coated lasers, indicating that the quantum-well material ͑i.e., strained-layer InGaAs͒, and not the cladding/ confinement layers material, primarily determines the COMD value.The cw output power of a diode laser is generally limited by either thermal rollover or COMD. Thermally limited power saturation can be eliminated by designing laser structures to have high total power conversion efficiencies, low threshold-current density, and weak temperature sensitivity for both the threshold current and the external differential quantum efficiency ͑i.e., high T 0 and T 1 values͒. 4 As previously reported, 4 the use of a double-quantum-well ͑DQW͒ InGaAs active region together with high-band-gap InGaAsP (E g ϭ1.62 eV͒ optical-confinement layers, leads to 0.98 m diode lasers with relatively temperature insensitive characteristics. Given a certain CO...

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The self-guiding of relativistically intense but ultrashort laser pulses has been experimentally investigated as a function of laser power, plasma density, and plasma length in the blowout regime. The extent of self-guiding, observed by imaging the plasma exit, is shown to be limited by nonlinear pump depletion with observed self-guiding of over tens of Rayleigh lengths. Spectrally resolved images of the plasma exit show evidence consistent with self-guiding in the plasma wake. Minimal losses of the self-guided pulse resulted when the initial spot size was matched to the blowout radius.

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