Tapered diode-pumped continuous-wave alexandrite laser

Abstract

We describe a low-cost and efficient alexandrite (Cr:BeAl 2 O 4 ) laser that is pumped by a high-brightness tapered diode laser (TDL). The tapered diode (TD) provides up to 1.1 W of output power and its wavelength can be finetuned to either 680.4 nm (R1 line) or 678.5 nm (R2 line) for efficient in-line pumping. Continuous-wave (cw) output powers of 200 mW, slope efficiencies as high as 38%, and a cw tuning range extending from 724 to 816 nm have been achieved. To the best of our knowledge, the cw power levels and slope efficiencies are the highest demonstrated so far from such a minimal complexity and low-cost system based on the alexandrite gain medium. Consequently, TDs operating in the red spectral region have the potential to become the standard pump sources for cw alexandrite lasers in the near future.

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

“…5, at crystal temperatures of 10 • C and 60 • C. The optimum wavelengths of 765 nm and 770 nm at 10 • C and 60 • C, respectively, are typical for Alexandrite [1,7,16]. Elevated temperatures extended the upper tuning range, as has been previously reported [2], but in turn increased the lower bound by 7 nm.…”

Analysis of pump excited state absorption and its impact on laser efficiency

“…The cavity loss L becomes a doubly important design parameter for systems with pump ESA, with regards to slope efficiency, as it reduces both η p and η c . The trend of slope efficiency with output coupling in Figure 5 has been seen in end-pumped Alexandrite lasers [14,15], which have pump ESA [16]. In these investigations it was suggested that this could be due to energy transfer upconversion -a process that had not been identified for Alexandrite in the literature.…”

“…The more exact formulations, (15) and (16), are also independent of σ 0 and N , assuming a suitably long gain medium and not excessive pumping (note I s is inversely proportional to σ 0 ).…”

InP/InGaP quantum-dot SESAM mode-locked Alexandrite laser

“…Unlike Ti:sapphire, Alexandrite can be directly pumped with red laser diodes because its absorption band covers most of the visible spectral range [10,13]. In addition, its larger στ product [15] presents a prospect of lower laser threshold. Furthermore, a diode-pumped Alexandrite laser was shown to produce >26 W of output power in the continuous wave regime [13] which significantly exceeds output from widely used Ti:sapphire lasers.…”