Semiconductor laser-diode-pumped solid-state lasers: status and future

Semiconductor laser diode pumping of solid-state lasers is an idea whose time has come. Early experiments in the 1960s proved the scientific feasibility of diode pumping, but the cryogenically cooled, relatively low-efficiency diodes of the day precluded demonstration of the high-efficiency, power, compactness, and operating life that the concept promises. Since then, the room-temperature efficiency, power, diode packing density, and life of AlGaAs laser diodes have increased spectacularly,1 largely due to the introduction of MOCVD wafer scale processing of single- and multiple-quantum-well diode structures: single-100-μm-wide-stripe laser diodes can produce >3-W cw and >8-W quasi-cw (150-μs pulse); centimeter long linear (bar) diode arrays can produce >13-W cw and >130-W quasi-cw; 2-D arrays of stacked bars can produce >3.3-kW/cm2 quasi-cw; high-power diodes are now approaching2 wall plug efficiencies of 60%. The recent availability of such high-performance laser diodes and arrays has enabled significant progress toward the full realization of the original vision.