Design of a High Performance Mid-IR Fiber Laser Based on Pr<sup>3+</sup>-Doped Fluoroindate Glass
Antonella Maria Loconsole, Vito Vincenzo Francione, Andrea Annunziato, Francesco Anelli, Francesco Prudenzano
Abstract
In this work, a novel continuous wave fiber laser, pumped at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\lambda }_p = \ 1550\ nm$</tex-math></inline-formula> and emitting at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\lambda }_s = \ 4\ \mu m$</tex-math></inline-formula> , has been designed and optimized. It is based on a step-index, double-cladding, praseodymium-doped fluoroindate glass fiber, available on market, having dopant concentration <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${N}_{Pr} = \ 8000\ ppm$</tex-math></inline-formula> . For a realistic design, measured spectroscopical parameters have been taken into account, writing a five-level rate equation model. The design is carried out by employing a homemade code solver. The best predicted slope efficiency of about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\eta \ = \ 33{\bm{\ \% }}$</tex-math></inline-formula> and pump power threshold <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${P}_{th} = {\bm{\ }}0.007\ W$</tex-math></inline-formula> have been obtained for a fiber length <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${L}_{fiber} = \ 0.4\ m$</tex-math></inline-formula> and output mirror reflectivity <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${R}_{out} = \ 30{\bm{\ \% }}$</tex-math></inline-formula> . These values are very interesting with reference to the state of the art and promise the fabrication of high beam quality optical sources in the middle infrared range, by employing conventional erbium-doped fiber pumping lasers, with a potentially easy all-in-fiber integration.