Analytical model of tunable Alexandrite lasing under diode end-pumping with experimental comparison

Abstract

An analytical model is formulated to support understanding and underpin experimental development of laser action in the promising diode end-pumped Alexandrite system. Closed form solutions are found for output power, threshold and slope efficiency that for the first time incorporate the combined effects of laser ground state absorption (GSA) and excited state absorption (laser ESA), along with pump excited state absorption (pump ESA), in the case of an end-pumping geometry. Comparison is made between model predictions and experimental results from a fibre-delivered diode end-pumped Alexandrite laser system, showing the impact of wavelength tuning, crystal temperature, laser output coupling, and intracavity loss. The model is broadly applicable to other quasi-three-level lasers with combined laser and pump ESA. A condition for bistable operation is also formulated.

Alexandrite: an attractive thin-disk laser material alternative to Yb:YAG?

“…The numerical method used is similar to what was recently described in [26] for the modeling of Cr:Colquiriite TDLs, but it is an extended and improved version. First of all, for Alexandrite we have to also include the effect of pump excited state absorption and self absorption losses [17,86,87]. Additionally, effect of usage of active multipass cell (AMC) cavities with an arbitrary number of bounces in the TD is also included [88][89][90].…”

Optical vortex generation from a diode-pumped alexandrite laser

“…Despite alexandrite's attractive and beneficial properties, diode-pumping with significant power has only recently been reported. In our previous work we demonstrated: record continuous-wave (CW) output powers of >26 W from a diode-pumped alexandrite laser, with slope efficiency 49 % [35]; high energy Q-switching and the first ever cavitydumped Q-switching of a diode-pumped alexandrite laser [36]; and we have reported analytical models that underpin our understanding and alexandrite laser design considerations [37]. There have been further reports of diode-pumping alexandrite lasers, using tapered diodes to in-band pump [38,39], with broad tunability [37,40] and alexandrite ring laser development [41].…”

Temperature dependence of Alexandrite effective emission cross section and small signal gain over the 25-450 °C range

“…On top of these, excited state absorption also exists in the pumping wavelength region of Alexandrite [31]. The effect of pump excited state absorption on pumping efficiency has been discussed in [14,32,33]; and its temperature dependence is investigated in [33].…”

“…However, the progress has been relatively slow especially for the development of ultrashort pulse laser/amplifier sources, and there is currently a need for better understanding of Alexandrite laser gain media, for accurate modeling of its laser potential. Recent detailed work by Kerridge-Johns et al on the effect of pump and laser excited state absorption on laser performance has been an important step towards this aim [14,32,33]; however, efforts in this direction face a challenge due to the limited availability of spectroscopic data. For a laser design engineer, a thorough modeling of laser dynamics and its potential as an efficient laser requires detailed knowledge of wavelength and temperature dependence of all the relevant cross sections (σ em , σ esa , and σ a ) as well as the temperature dependence of fluorescence lifetime (τ F ).…”