Acoustically tuned erbium-doped fiber ring laser

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Abstract
We report what is to our knowledge the first narrow-linewidth, continuously tunable laser that uses an acousto-optic filter to achieve a broad tuning range. The unidirectional ring-laser configuration incorporates an erbium-doped fiber amplifier as the gain medium and an integrated, frequency-shift-compensated acousto-optic filter as the tuning element. Using a 980-nm optical pump with 60 mW of launched power, we obtained nearly 2 mW of laser output with 10% output coupling. A tuning range of 40 nm was achieved, centered about 1545 nm. Single-longitudinal-mode operation with a 10-kHz linewidth was demonstrated, although the laser wavelength hopped between nearby longitudinal modes because of path-length fluctuations. Wavelength switching at rates up to 100 kHz was examined.