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A cw Ti:A1(2)O(3) ring laser with a threshold power of 119 mW is demonstrated. It provides a tunable source of single-frequency, diffraction-limited radiation that is suitable for injection seeding. The Ti:A1(2)O(3) laser is operated with a diode-laser-pumped, frequency-doubled, Nd:YAG laser as the sole pump source.

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We have demonstrated ultra-high efficiency amplification in Tm-doped fiber with both core- and cladding-pumped configurations using a resonant tandem-pumping approach. These Tm-doped fiber amplifiers are pumped in-band with a 1908 nm Tm-doped fiber laser and operate at 1993 nm with >90% slope efficiency. In a core-pumped configuration, we have achieved 92.1% slope efficiency and 88.4% optical efficiency at 41 W output power. In a cladding-pumped configuration, we have achieved 123.1 W of output power with 90.4% optical efficiency and a 91.6% slope efficiency. We believe these are the highest optical efficiencies achieved in a Tm-doped fiber amplifier operating in the 2-micron spectral region.

A fiber-optic linear accelerometer based on intensity modulation produced by lateral displacement of a cantilevered fiber has been fabricated and tested. The model reported on is constructed with multimode fiber and has a displacement sensitivity of 6.4 x 10(-13) m. The device has general application as a linear accelerometer with the inherent advantages of remote optical fiber sensing. Particular attention is given to sono-buoy hydrophone applications in which the present model has a sensitivity limit corresponding to 75 dB relative to 1 microPa at 1 kHz. Means for substantially improving the accelerometer's sensitivity as a hydrophone are discussed.