Optical: systems and elements – Optical amplifier – Particular active medium
Patent
1998-05-01
2000-10-31
Hellner, Mark
Optical: systems and elements
Optical amplifier
Particular active medium
372 34, H01S 300, H01S 304
Patent
active
061411434
ABSTRACT:
A solid state laser amplifier includes a diode pump source and a crystal capable of lasing light at a fundamental wavelength. The source is directed into the crystal, and a seed beam is also coupled along an input path into the crystal to initiate lasing, which amplifies the seed beam. The amplifier is intended for intermittent use, or use over a wide range of input power levels, so that variations of the energy input and output give rises to extreme thermal challenges. To manage heat stress in the amplifier crystal, both the pump beam and the seed beam are directed into the crystal through a cap of undoped material which is non-absorbent at the seed or pump wavelength, and is diffusion bonded to the crystal, thus serving as a thermal reservoir and allowing the laser to operate over a broad power band, with high gain over an extended range of saturation values, and to maintain stable operation during intermittent or changing operation of the seed laser. In a preferred embodiment the crystal is pumped from both ends by separate diode sources, with a continuous wave pump power of 10-40W or more, and utilizes a vanadate crystal which lases at the band of a garnet or vanadate laser, providing a gain of two or more over an input seed beam power range from milliwatts to ten watts or more. The amplifier may operate as a single-pass amplifier, with direct output of the amplified beam, or it may employ a return mirror which reflects the amplified beam back into the crystal and results in increased gain. When used with a return mirror, the output beam is separated from the seed path by an assembly such as a polarization coupling assembly, e.g., a Faraday rotator and polarization beam splitter. The pump source may be a packaged diode array having bundled diode outputs that provide a high power but relatively poor quality beam, which is directed by one or more relay lenses into the crystal. The seed beam is coupled centrally into the pump mode volume, so that an amplified beam of higher quality is produced. The amplifier is a simple and effective unit to upgrade a prior generation YAG laser or medical laser console, such as ophthalmic or dermatologic clinical laser system, essentially doubling its power while allowing the console to operate with its existing pulse selection and power control circuitry.
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Hellner Mark
Light Solutions Corporation
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