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Excited-state absorption measurement of Tm3+-doped crystals

Excited-state absorption measurement of Tm3+-doped crystals
Excited-state absorption measurement of Tm3+-doped crystals
The excited-state absorption (ESA) spectra from the long-lived 3F4 energy-level of several crystals doped with trivalent thulium (Tm3+) ions have been measured using a pump-probe technique employing high-brightness narrowband (FWHM ~15 nm) light emitting diode (LED) as the probe. Our aim is to determine the strength of ESA channels at wavelengths addressable by commercially available laser diodes around 630-680 nm, pivotal for building waveguide upconversion lasers. The favorable lifetime of the 3F4 energy-level and negligible ground-state absorption for the red-wavelength second-step excitation, ensures a direct and efficient excitation route for a dual-wavelength pumping scheme of the thulium ion, which will enable blue-green laser emission from its 1G4 manifold.
ESA measurements in the red spectral region were conducted at room temperature utilizing the pump-probe technique. The advantage of the LED probe over a broadband incandescent lamp is that stimulated-emission at the probe wavelength can be eliminated, simplifying the analysis of the measurement and the determination of the magnitude of the ESA cross-section. Four Tm-doped crystalline hosts Y3Al5O12 (YAG), YAlO3 (YAP), LiYF4 (YLF), and KYGdLu(WO4)2 (KYGdLuW) were investigated, with polarized ESA spectra measured for the non-isotropic samples. Excitation of the Tm3+ ions into the intermediate 3F4 manifold was achieved via non-radiative and cross-relaxation energy transfer from the 3H4 manifold, pumped by a current-modulated fibre-coupled GaAs laser diode operating at ~790 nm. To ensure that ESA at all wavelengths of interest were resolved, the LED's spectra were tuned via the modulated drive-current amplitude and junction temperature. As such, with direct pump and probe modulation, we eliminated the need for mechanical choppers, simplifying the optimization of frequency-resolved ESA measurements needed to isolate the other possible ESA transition (3H4 to 1D2). Vastly improved ESA spectra have been obtained with respect to those reported in the literature.
Szela, J.W.
9870e84b-57a8-4b8d-b9fb-dfec0688c20a
Mackenzie, J.I.
1d82c826-fdbf-425b-ac04-be43ccf12008
Szela, J.W.
9870e84b-57a8-4b8d-b9fb-dfec0688c20a
Mackenzie, J.I.
1d82c826-fdbf-425b-ac04-be43ccf12008

Szela, J.W. and Mackenzie, J.I. (2012) Excited-state absorption measurement of Tm3+-doped crystals. SPIE Photonics Europe 2012, Brussels, Belgium. 16 - 19 Apr 2012. (doi:10.1117/12.922673).

Record type: Conference or Workshop Item (Paper)

Abstract

The excited-state absorption (ESA) spectra from the long-lived 3F4 energy-level of several crystals doped with trivalent thulium (Tm3+) ions have been measured using a pump-probe technique employing high-brightness narrowband (FWHM ~15 nm) light emitting diode (LED) as the probe. Our aim is to determine the strength of ESA channels at wavelengths addressable by commercially available laser diodes around 630-680 nm, pivotal for building waveguide upconversion lasers. The favorable lifetime of the 3F4 energy-level and negligible ground-state absorption for the red-wavelength second-step excitation, ensures a direct and efficient excitation route for a dual-wavelength pumping scheme of the thulium ion, which will enable blue-green laser emission from its 1G4 manifold.
ESA measurements in the red spectral region were conducted at room temperature utilizing the pump-probe technique. The advantage of the LED probe over a broadband incandescent lamp is that stimulated-emission at the probe wavelength can be eliminated, simplifying the analysis of the measurement and the determination of the magnitude of the ESA cross-section. Four Tm-doped crystalline hosts Y3Al5O12 (YAG), YAlO3 (YAP), LiYF4 (YLF), and KYGdLu(WO4)2 (KYGdLuW) were investigated, with polarized ESA spectra measured for the non-isotropic samples. Excitation of the Tm3+ ions into the intermediate 3F4 manifold was achieved via non-radiative and cross-relaxation energy transfer from the 3H4 manifold, pumped by a current-modulated fibre-coupled GaAs laser diode operating at ~790 nm. To ensure that ESA at all wavelengths of interest were resolved, the LED's spectra were tuned via the modulated drive-current amplitude and junction temperature. As such, with direct pump and probe modulation, we eliminated the need for mechanical choppers, simplifying the optimization of frequency-resolved ESA measurements needed to isolate the other possible ESA transition (3H4 to 1D2). Vastly improved ESA spectra have been obtained with respect to those reported in the literature.

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More information

e-pub ahead of print date: 2012
Venue - Dates: SPIE Photonics Europe 2012, Brussels, Belgium, 2012-04-16 - 2012-04-19
Organisations: Optoelectronics Research Centre

Identifiers

Local EPrints ID: 363223
URI: https://eprints.soton.ac.uk/id/eprint/363223
PURE UUID: 4ba6b1f4-4f0a-498f-bec5-8ce6048fd8d6
ORCID for J.I. Mackenzie: ORCID iD orcid.org/0000-0002-3355-6051

Catalogue record

Date deposited: 20 Mar 2014 16:57
Last modified: 29 Oct 2019 01:56

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