High efficiency cw alexandrite laser operation has been achieved. With longitudinal pumping by a krypton laser in a nearly concentric cavity, a 51% output power slope efficiency has been measured. Including the transmission at the input coupler mirror, a quantum yield of 85% has been attained above threshold. Tunability from 726 to 802 nm has also been demonstrated. The low loss and good thermal properties make alexandrite ideal for cw laser operation.

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The emission cross section σc for GSGG:Cr has been calculated following the approach outlined in Ref. 1. Based on the fluorescence spectrum, fluorescence lifetime (assumed to be radiative), and assuming the index of refraction to be 1.92, the σc at room temperature is 8.2×10−21cm2 at 776 nm (lasing wavelength in Ref. 7), compared with 7×10−21cm2 at 752 nm for alexandrite calculated with the same approach.
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11.
Dye LD‐700 is supplied by Exciton, Incorporated, Dayton, Ohio. With 4‐W pumping at 647.1 nm, 1.2‐W output at 750 nm has been measured.
12.
1.4 W of tunable output has been achieved from a 1‐cm‐long sample at 8 W (all lines) absorbed power from an argon laser. The output mirror transmission is 0.75%, the total cavity loss 1.54%, and the measured slope efficiency 32%. Chopping is required to reduce heating in this case.
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