Adjustable modules for high-power (over 7.5-mW CS) coupling of diode lasers to single-mode fibers

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Abstract
Single-mode (SM) fiber output power of over 7.5-mW CW has been obtained in unique adjustable coupling modules. These are the highest powers ever reported coupled between diode lasers and single-mode fibers. Coupling efficiencies over 30 percent were obtained in simple butt-coupling by taking advantage of the large mode size available from RCA constricted-double-heterojunction large-optical cavity (CDH-LOC) lasers. We also observed peak fiber power of over 9 mW with 100-ns 50-percent duty cycle pulses. The minature modules provide relative transverse and lateral motion between fiber and laser with 2000-Å resolution, allowing fine tuning against long-term drifts. The coupling, while adjustable, is still stable against moderate acceleration of module and motion of fiber pigtail. The adjustments may be adapted to servo control.