Excited-state absorption measurements of Tm³⁺-doped crystals

Abstract

High resolution, absolute excited-state absorption (ESA) spectra, at room temperature, from the long-lived 3 F 4 energy level of several crystals doped with trivalent thulium (Tm 3+ ) ions have been measured employing high-brightness narrowband (FWHM <30 nm) light emitting diodes (LEDs) as a probe wavelength. The aim of this investigation was to determine the strength of ESA channels at wavelengths addressable by commercially available semiconductor laser diodes operating around 630-680 nm. The favourable lifetime of the 3 F 4 manifold and negligible ground-state absorption (GSA) for the red-wavelength second-step excitation, ensures a direct and efficient route for a dual-wavelength pumping scheme of the thulium ion, which will enable blue-green laser emission from its 1 G 4 upper-laser level.