We have developed an efficient room-temperature ytterbium-doped YAG laser operating at 1.03 microm pumped by an InGaAs strained-layer diode laser operating at 968 nm. The threshold was 234 mW and 23 mW of output power was obtained for an absorbed pump power of 345 mW. This laser offers a number of advantages over AlGaAs pumped Nd:YAG lasers, such as broader absorption features, longer fluorescent lifetime, and lower thermal loading of the gain medium.
The rapid exchange of data with underwater sensors and systems is increasingly valuable for oceanography, oil exploration and other investigations of undersea phenomena. This paper reviews the potential, as well as the limitations, of acoustic, radio-frequency electromagnetic, fiber-optical
and free-space optical techniques for high-bandwidth, undersea communication. In particular, we discuss the environmental and hardware attributes that bound the performance of free-space optical communications in a variety of undersea scenarios. Free-space optical approaches are capable of
providing data bandwidths approaching 109 bits per second (bps) under suitable environmental conditions. More commonly, 10-100 × 106 bps can be achieved over ranges approaching 100 meters. Turbid water and high-ambient light conditions (primarily from downwelling
sunlight) pose a serious challenge to performance at moderate and long ranges.
We have achieved efficient room-temperature flash-lamp-pumped laser operation in titanium-doped sapphire. The laser has a threshold of 20 J, a slope efficiency of 0.5%, an output energy in excess of 300 mJ, and a tuning range (with our present optics) of 720-920 nm. Ways of reducing the lasing threshold and increasing slope efficiency are discussed.
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