Gain and saturation intensity of the green Ho:ZBLAN upconversion fiber amplifier and laser

Abstract

The gain and saturation intensity of the green Ho-doped fluorozirconate (ZBLAN) glass fiber amplifier and laser, pumped in the red (643 /spl les/ /spl lambda//sub p/ /spl les/ 649 nm; <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> /spl larr/ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> I/sub 8/), have been measured. For a 2.4-μm core diameter fiber 45 cm in length, the single-pass gain at 543.4 nm exceeds 12 dB for 90 mW of pump power at 643.5 nm. The saturation power for the <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> , <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /spl rarr/ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> I/sub 8/ lasing transition was determined from gain measurements to be 970 /spl plusmn/ 175 μW, which corresponds to a saturation intensity of 19.8 /spl plusmn/ 3.5 kW /spl middot/ cm/sup -2/, and a stimulated emission cross section approximately one order of magnitude larger than theoretical estimates.