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AIP conference proceedings

The photon avalanche laser

Mark E. Koch, William E. Case

Published Jan 1, 1986• 5 citations
Publisher

Abstract

Laser output at 4.9 μm has been obtained from a Pr doped LaCl3 crystal. Pump laser energy at 529 nm is coupled into the crystal via the photon avalanche process. This process involves metastable state ion absorption of a pump photon and subsequent ion‐ion energy transfer. The latter step generates two metastable state ions (self‐induced absorption). This highly nonlinear process is characterized by a sharp onset with pump intensity and, at higher intensities, depopulation of the ionic ground state. Experimental results will be compared with predictions from an existing rate equation model.

DOI
10.1063/1.35881

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Avalanche-like behavior of up-conversion luminescence by nonlinear coupling of pumping rates

M. V. Korolkov, I. A. Khodasevich, A. S. Grabtchikov +2 more

Here we report and discuss the avalanche-like up-conversion behavior in absence of the avalanche. We experimentally observed significant changes in the slope of the curve for the intensity dependence of up-conversion luminescence of erbium ions in the green band (520-560 nm) on the pump intensity of the diode laser. Such changes are typical for the photon avalanche. However, the concentration of erbium ions is insufficient for an efficient exchange of energy between them, and the excitation of a photon avalanche is not possible. Using a simple three-level approximation of the up-conversion process model, we have shown that the observed avalanche-like luminescence process can also occur in the absence of a photon avalanche due to the nonlinear relation between the efficiency of two pumping channels of erbium ions caused by the intensity dependence of the pump spectrum.

arXiv:1911.13069•Optics Letters•Nov 27, 2019•5 citations
Laser output at 4.9 μm has been obtained from a Pr doped LaCl3 crystal. Pump laser energy at 529 nm is coupled into the crystal via the photon avalanche process. This process involves metastable state ion absorption of a pump photon and subsequent ion‐ion energy transfer. The latter step generates two metastable state ions (self‐induced absorption). This highly nonlinear process is characterized by a sharp onset with pump intensity and, at higher intensities, depopulation of the ionic ground state. Experimental results will be compared with predictions from an existing rate equation model.
We have made an unexpected discovery of highly nonlinear optical behavior in certain praseodymium-doped lanthanum halides. When a LaCl3 or LaBr3 crystal containing Pr3+ ions is exposed to green laser radiation slightly in excess of a certain critical intensity, Pr fluorescence increases by orders of magnitude. Infrared output near 4.5-μm wavelength is associated with the large visible output, and pump power is strongly absorbed. We call this new phenomenon a photon avalanche. Critical pump power density is in the 1–15 W/cm2 range. At higher pump rates, a population inversion and lasing action take place between the lowest infrared levels of the Pr ion. Experimental results are presented and compared to predictions of a photon avalanche model based on resonant energy transfer.
We report an investigation of a nonlinear optical absorption phenomenon observed in LaCl3 crystals doped with Pr. When these crystals are illuminated with a laser beam of 529 nm wavelength and intensity in excess of a certain critical value, the light is strongly absorbed. The laser radiation is resonant with a Pr3+ transition from the first excited state (3H5) to a high optical state (3P1), and absorption is accompanied by strong fluorescence output from 3p1 and 3p0 to several lower-lying levels. Since the resonant transition does not include the ground state, it is not expected a priori that any absorption should occur (see Fig. 1). This is an example of the so-called photon avalanche phenomenon1.
The phenomenon of photon avalanche, which involves both an excited state absorption process from a metastable level and a cross relaxation energy transfer process responsible for the large increases in population of this metastable level, has been investigated in LaCl3:Pr3+.{\mathrm{LaCl}}_{3}:{\mathrm{Pr}}^{3+}.LaCl3​:Pr3+. In this paper, we report on the intensity dependence of both the steady-state fluorescence and the temporal evolution of the avalanche signal as a function of temperature (80 K to room temperature). Comparisons are made between experimental results and mathematical models based on a six-level system described by a series of coupled rate equations combined with the propagation of a Gaussian beam. We develop a model with only one adjustable parameter, the excited state absorption cross section, which provides a good description of all of our experimental data. We have estimated values of the excited state absorption cross section for the various ${}^{3}{\stackrel{\ensuremath{\rightarrow}}{{\mathrm{H}}_{5}}}^{3}{\mathrm{P}}_{0}$ pumping transitions at different temperatures.
Here we report and discuss the avalanche-like up-conversion behavior in absence of the avalanche. We experimentally observed significant changes in the slope of the curve for the intensity dependence of up-conversion luminescence of erbium ions in the green band (520-560 nm) on the pump intensity of the diode laser. Such changes are typical for the photon avalanche. However, the concentration of erbium ions is insufficient for an efficient exchange of energy between them, and the excitation of a photon avalanche is not possible. Using a simple three-level approximation of the up-conversion process model, we have shown that the observed avalanche-like luminescence process can also occur in the absence of a photon avalanche due to the nonlinear relation between the efficiency of two pumping channels of erbium ions caused by the intensity dependence of the pump spectrum.