Photon Avalanche Upconversion Research Articles

Advances in up-conversion lasers based on Er3+ and Pr3+

The present work gives an overview of room-temperature up-conversion laser systems operating in the visible spectral region. In addition to the theoretical description of the up-conversion and photon-avalanche up-conversion mechanisms, two rare-earth ions in fluoride hosts are presented in detail: erbium and praseodymium. Using a multi-pass pumping set-up, green erbium up-conversion lasing at 552 nm is demonstrated in LiLuF4 under laser-diode pumping. In addition, laser operation of three different ytterbium co-doped praseodymium systems at several wavelengths is presented. A common property of the host materials LiLuF4, LiYF4, BaY2F8, and ZBLAN is their low phonon energy, which makes them favorable for up-conversion and photon-avalanche up-conversion laser systems.

Infrared-laser induced photon avalanche upconversion in Ho3+–Yb3+ codoped fluoroindate glasses

An intense green upconversion emission due to a photon avalanche mechanism has been observed in Ho3+–Yb3+ codoped fluroindate glasses, measured at 200 K, under excitation at around 750 nm. The influence of the Yb3+ concentration on the photon avalanche process has been studied. The pump power threshold of the avalanche mechanism decreases as the Yb3+ concentration is increased. A reduction by about a factor of 3 is observed from the 2.25 mol % Ho3+ single doped glass to the 2.25 mol % Ho3+–2.25 mol % Yb3+ codoped glass. This effect has been related to an extra feeding of the I47 intermediate level of Ho3+ ions via Ho3+→Yb3+ and Yb3+→Ho3+ energy transfer and back transfer processes, respectively.

Room temperature photon avalanche up-conversion in Ho3+ doped fluoroindate glasses under excitation at 747 nm

Abstract The room temperature up-conversion spectrum of a fluoroindate glass doped with 2.5 mol% of Ho3+ has been detected under excitation at 747 nm. Blue, red and very intense green bands are observed. The green emission has been analysed in detail, in order to investigate the efficient up-conversion mechanism involved in this transition. The low absorption cross-section for the transition from the ground state 5I8 to 5I4, the excitation spectrum of the 5S2, 5F4 → 5I8 green emission, based on a strong excited state absorption (5I7 → 5S2, 5F4) and the temporal dynamics of the process indicate that a photon avalanche mechanism occurs.

Photon avalanche upconversion in LiKYF 5 crystals doubly doped with Tm 3+ and Er 3+

For the first time red-to-blue photon avalanche upconversion has been discovered and investigated in LiKYF 5 crystals doubly doped with Tm 3+ and Er 3+ under laser excitation at the liquid nitrogen temperature. On the basis of the optical studies, an original model of the luminescent mechanisms, within which the Er 3+ ions act as both donor and acceptor, and as a result sensitize the photon avalanche effect in Tm 3+ by converting the optical excitation energy in its diffusion among the Tm 3+ ions, is presented. It is assumed that all these mechanisms can be realized when the Er 3+ concentration in crystals is relatively low in order to avoid direct interactions between the Er 3+ ions.

Room temperature photon avalanche upconversion in Tm3+-doped fluoroindate glasses

Intense blue upconversion emission has been observed at room temperature under excitation in the range of 630 - 660 nm in a fluoroindate glass doped with 2.5 mol% of Tm3+. The experimental dynamics and power dependence of this emission are well described using a photon avalanche model based on the mean field approximation.

Photon-avalanche upconversion in thulium-doped lutetium aluminum garnet

Strong blue fluorescence at 487 nm corresponding to the (1)G(4) --> (3)H(6) transition was generated from Tm(3+)-doped lutetium aluminum garnet on excitation with a 618-nm dye laser as a result of a photon-avalanche upconversion mechanism.

Growth by liquid phase epitaxy and characterization of Nd:YLiF4 layers

We report the growth of Nd:YLiF4 layers using liquid phase epitaxy. Fluorescence decays were measured at different temperatures, 1.05 μm laser performances have been investigated and photon avalanche up-conversion has been observed up to 60 K.

Photon avalanche upconversion in various Tm3+-doped materials

We demonstrate the good agreement between theory and experimental results concerning the effect of the rare-earth ion concentration, the metastable state lifetime and the nonresonant ground state absorption cross section on the photon avalanche efficiency.

Up-conversion of multi-site Er in LiNbO 3 single-crystal fibers

In this work, the near infrared to visible up-conversion process was studied in Er 3+ doped LiNbO 3 single-crystal fibers. The absorption spectra of the 4I 9 2 multiplet and site-selective excitation of up-converted emission from the 4S 3 2 multiplet were measured at 10 K. Multiple sites for Er 3+ were found to exist in the fiber samples. They fall into two groups which may be related to the substitution of Li and Nb by Er. Near-infrared excitation spectra of the up-conversion and transient dynamics have shown that either excited state absorption (ESA) or energy transfer up-conversion (ETU) processes play dominant roles at certain pump wavelengths. In addition, laser-heating-induced up-conversion or photon avalanche up-conversion may also take place at some pump wavelengths.

Multiphonon pumping in Er3+ ZBLAN bulk and fibre, the first step for the photon avalanche process

Based on the understanding of the role played by the multiphonon sideband absorption as the initial step in photon avalanche up-conversion, such an effect in Er3+ and in a ZBLAN glass and fibre at room temperature was obtained for the first time. The pump wavelength is far from any electronic absorptions from the ground state of the Er3+ ion, but corresponds to excited state absorption. The distinct characteristics such as rise time, threshold and non-linear dependence on pumping have been demonstrated. The dynamic process of the photon avalanche has been analyzed and mechanisms are proposed.

Room-temperature photon avalanche up-conversion in Er-doped fluoride glass and fibre pumped at 700 nm

A strong emission at 550 nm as well as a series of other wavelengths have been observed in Er-doped ZrF4-BaF2-LaF3-AlF3-NaF fibres and bulk glass at room temperature when the excitation wavelength is about 700 nm, which is far away from the absorptions from the ground state of Er3+ ions. Measurements of excitation, time delay and intensity dependence versus pump power suggest that these emissions are caused by the photon avalanche effect originating from the multiphonon side-band absorption. The excitation mechanisms of this photon avalanche have been analysed. Spectral measurement also show some strong emissions in the IR region, some features of which are probably linked with laser action.

Photon avalanche upconversion in Er/sup 3+/:YAlO/sub 3/

The results of an investigation of photon avalanche upconversion pumping in Er/sup 3+/:TiAlO/sub 3/ are reported. Five pump wavelengths corresponding to transitions from the metastable /sup 4/I/sub 13/2/ state to the /sup 2/H/sub 11/2/ state generated upconversion laser emission at 549.8 nm. The dependence of the laser output power on pump power near laser threshold is discussed in terms of a four-level kinetics model and is shown to reflect the threshold power requirement for photon avalanche. The maximum output power at 7 K was 33 mW, giving an optical conversion efficiency of 3.5% and a conversion efficiency of 28% based on absorbed power. Pumping Er:YALO by cross relaxation energy transfer produced 166 mW of laser output with an optical conversion efficiency of 17%.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Room temperature photon avalanche up-conversion in Er-doped ZBLAN glass

Photon avalanche up-conversion emission at 550 nm with a steep threshold has been observed in Er-doped ZBLAN glass. This is, to the best of our knowledge, the first time that this effect was found for Er3+ ion, in a glass, and at room temperature. The excitation wavelength is 579.2 nm which is far away from any electronic absorption from the ground state. An extremely long rise time of the signal of up to about 4 s has been observed for the up-converted emission at 550 nm. An excitation mechanism of this photon avalanche process is proposed.

Er/sup 3+/:YAlO/sub 3/ upconversion laser

Upconversion lasing in Er:YAlO/sub 3/ is reported. Laser emission was produced using both sequential two-step pumping and cross-relaxation energy transfer. In addition, photon avalanche upconversion pumping was demonstrated. Selection among these pumping mechanisms is determined by the pump wavelength, and laser operation was obtained with excitation between 785 nm and 840 nm. The highest laser output power was achieved at 34/spl deg/K, where 918 mW of pump power at 807 nm produced 121 mW of TEM/sub 00/ emission. The optical conversion efficiency was 13%. Repetitively Q-switched operation is reported, and the temporal- and temperature-dependence of the laser output is discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>