15 February 2012 Gain tailoring model and improved optical extraction in CW edge-pumped disk amplifiers
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Abstract
The effect of gain tailoring upon the optical extraction and OPD in a CW edge-pumped disk amplifier is examined using a two-dimensional model of diode pumping coupled with a two-dimensional, geometric model of optical extraction by a Gaussian profile beam from a Yb:YAG medium1. The gain medium is described by the well-known quasi-three level model of Beach2,3. Gain tailoring is accomplished by focusing the diode pump beam using cylindrical lenses. The diode pump beam, optical extraction, and gain medium models are described after which the pump absorption efficiency, energy deposition uniformity, output energy, and maximum peak-to-valley (PV) OPD are examined as a function of the pump lens focal length and output aperture radius as well as amplifier input seed energy, number of roundtrip amplifier passes, and diode pump power. It is shown that using pump beam focusing to tailor the gain radially deposits more energy in the central region of the disk and thus results in improved optical extraction because a Gaussian input optical beam preferentially accesses the central region of the disk. With gain tailoring one can achieve the same amplifier output energies as without gain tailoring but using less pump power and/or amplifier seed energy, resulting in reduced disk heating and diode-pump waste heat. Although the maximum PV OPD is larger, the central region of the thermally-induced OPD remains relatively uniform, allowing one to increase the output energy with only modest increases in the effective OPD.
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Drew A. Copeland, John Vetrovec, "Gain tailoring model and improved optical extraction in CW edge-pumped disk amplifiers", Proc. SPIE 8235, Solid State Lasers XXI: Technology and Devices, 82350U (15 February 2012); doi: 10.1117/12.910301; https://doi.org/10.1117/12.910301
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