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Quadrature Frequency Resolved Spectroscopy of Upconversion Photoluminescence in GeGaS: Er3+; I. Determination of Energy Transfer Upconversion Parameter

Autoři: Střižík Lukáš | Prokop Vít | Hrabovský Jan | Wágner Tomáš | Aoki Takeshi

Rok: 2016

Druh publikace: ostatní - přednáška nebo poster

Strana od-do: nestránkováno

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Jazyk	Název	Abstrakt	Klíčová slova
eng	Quadrature Frequency Resolved Spectroscopy of Upconversion Photoluminescence in GeGaS: Er3+; I. Determination of Energy Transfer Upconversion Parameter	The upconversion photoluminescence (UCPL) processes in rare-earth-doped materials comprise ground state absorption (GSA) followed by excited state absorption (ESA) and/or energy transfer upconversion (ETU) and occasionally photon-avalanche due to cross-relaxation process. The UCPL is analyzed usually by absorption-excitation spectroscopy and time-resolved spectroscopy (TRS). The TRS of UCPL is governed by nonlinear dynamics with a set of nonlinear rate equations, which cannot be always solved uniquely. By contrast quadrature frequency resolved spectroscopy (QFRS) of PL is highly sensitive due to sinusoidal modulation of DC-bias light and phase-sensitive detection, where the modulating perturbation can linearize the nonlinear dynamics thereby giving physical parameters. We have applied QFRS on green (λ ≈ 550 nm) UCPL in Er3+-doped GeGaS glass with modulating 975 nm laser and observed double-peaked spectra composed of long lifetime components τ1 ~ 0.2–2 ms and short lifetime τ2 ≈ several tens of μs. The Fig. 1 demonstrates the QFRS spectra being different in Er concentration and excitation power, which is explained by the difference of UCPL mechanism i.e., GSA/ESA and GSA/ETU using 3-level model (Er3+ ground state 4I15/2, intermediate level 4I11/2 of lifetime τ1, coupled upper states 4F7/2, 2H11/2, 4S3/2 of lifetime τ2). ETU parameter w (s-1) is determined by analyzing the model in terms of transfer function.	upconversion photoluminescence; quadrature frequency resolved spectroscopy; perturbation on rate equation; modelling for optional energy levels; energy transfer upconversion; Er-doped chalcogenides

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