Effect Of Yb3 Research Articles

Radiative trapping effect of Yb3+ ions in lead-germanate glasses

Yb is a good candidate as a pump source because there are only two manifolds in the Yb energy level scheme, the F7/2 ground state and the F5/2 excited state, and thus concentration quenching and excited-state absorption should not affect the lasing or the excitation wavelength [1]. Extensive investigations have been of Yb-doped glasses, fibers, and crystals [2–5]. The relatively long fluorescence lifetime, as well as the broad absorption and emission bands, is more prominent for Yb-doped glasses than for crystals, making the glasses attractive for diode-pumped generation of ultra-short pulses, high-power ultra-short pulse amplification and tunable laser sources [6]. In addition, the ability to achieve high concentrations of Yb ions and low loss also triggered the rapid development of various Yb-doped glasses such as phosphate, borate, and silicate glasses. However, up to now, there are few systematic investigations of the optical properties of Yb-doped germanate glasses. In this work, the spectroscopic properties of germanate glasses with different concentrations of Yb ions and different thicknesses were investigated. Glasses with compositions (mol%) 10Na2O–60GeO2– 30PbO–xYb2O3 (x = 0.2, 0.6, 1.0, 1.4, and 2.0) were prepared using regent-grade powders Na2CO3, Pb3O4, and high purity GeO2 (>99.999%). Yb 3+ was introduced as Yb2O3 with 99.9% purity. Batches of 20 g were well mixed in appropriate proportions and melted at 1050 C in a covered alumina crucible in a SiC-resistance electric furnace. The liquids were held for 15 min and the homogenous bubble-free melts were cast on a stainless plate preheated at about 150 C. The samples were well annealed in a muffle furnace to reduce thermal stress. The annealed samples were cut using a low-speed diamond saw and polished with 5 lm diamond paste. Plates of dimensions 20 mm · 10 mm · 2 mm with two polished faces were used for optical measurements. The refractive index of the studied glass was measured using the Brewster angle method. The density of the sample was measured using the Archimedes’ liquidimmersion method on an analytical balance with a precision of 0.0001 g. Absorption spectra of the glass sample were recorded with a Perkin-Elmer-Lambda 900UV/VIS/NIR spectrophotometer in the range 850–1100 nm. Fluorescence measurements were performed with a 940 nm diode laser excitation and detected by a TRIAX550 spectrophotometer controlled by a computer. The infrared fluorescence lifetime was determined by modulating the pump laser diode drive current with a square-pulse duration of 40 ms at a repetition of 10 Hz. All the measurements were performed at room temperature. The important spectroscopic parameters required include the effective emission and absorption cross sections of the F5/2 fi F7/2 transition and the upper laser level lifetimes of Yb. The emission cross section can be determined by either the method of reciprocity or the Fuchtbauer–Ladenburg formula. On the basis of the reciprocity method described by McCumber [7], the emission cross section, remi can be calculated from the measured absorption cross section, rabs, i.e.

Hot emission in Nd3+/Yb3+:YAG nanocrystalline ceramics

A visible emission of Nd3+ in the double doped Nd/Yb:YAG nanocrystalline ceramics was observed under intense CW excitation by 976nm laser diode. The observed emission is assigned by us to hot emission and it strongly increased with temperature. Its intensity exhibited long emission build-up times (of an order of seconds) after turning on the excitation source. The intensities of hot emission of Nd3+ ion increased with the excitation power demonstrating the IN dependence. It was found that N was proportionally dependent on the energy distance ΔE=Eemhot−E(4F3/2). The effect of Yb3+ concentration on hot emission intensity was also noticed. No Nd3+ emission from 4F3/2 level under indirect 976nm excitation was observed. The mechanisms leading to the visible hot emission in Nd/Yb:YAG nanocrystalline ceramics are discussed.

Effect of Yb3+ doping on upconversion emission intensity and mechanism in Er3+/Yb3+-codoped fluorozirconate glasses under 800 nm excitation

Er 3+ singly- and Er3+/Yb3+-codoped fluorozirconate glasses were prepared. The upconversion emission intensities of the Er3+ ion around both 550 and 660 nm were measured under 800 nm excitation. The absorption band of the Yb3+ ion is located around 980 nm. Though the absorption band of Yb3+ does not interact directly with the incident light at 800 nm, both upconversion intensities around 550 and 660 nm emission increased with the increasing YbF3 concentration. We calculated the upconversion intensities around 550 and 660 nm by using rate equations and evaluated the principal upconversion mechanism in Er3+ singly- and Er3+/Yb3+-codoped samples quantitatively. We also investigated the reason for the increase of the upconversion emission intensities with the codoping of Yb3+ under 800 nm excitation.

On the observation of 2.8 μm emission from diode-pumped Er3+- and Yb3+-doped low silica calcium aluminate glasses

In this letter, we investigate the midinfrared photoluminescence of a series of diode-pumped Er3+-doped and Er3+, Yb3+-codoped low-silica content aluminosilicate glasses. Emission at 2.8 μm was observed in both single doped and codoped samples. The effect of Yb3+ codoping of the Er3+-doped samples was such that, for example, for a 2 wt % Er3+-doped, the photoluminescence yield at 2.8 μm was found to be roughly three times larger than that of the single 2 wt % Er3+-doped sample. This behavior was attributed to the efficient sensitization of Er3+ by Yb3+ in our oxide based host glasses. The results reported in this letter, together with the outstanding mechanical, chemical, and thermal properties of these glasses, suggest that rare-earth doped calcium aluminate glasses may become an attractive host for the development of solid state lasers operating in the midinfrared.

Effect of Yb3+‐Codoping on the Upconversion Emission Intensity in Er3+‐Doped ZBLAN Fluoride Glasses under 800‐nm Excitation

The effect of Yb3+‐codoping on the upconversion emission intensity in Er3+‐doped ZBLAN fluoride glasses is investigated. The codoping of Yb enhanced the emission intensity for the samples excited by an 800‐nm laser diode beam. The enhancement in a constant YbF3 content (2 mol%) increased with increasing ErF3 content was about 70% of the initial value at 550 nm for the glasses containing 8 mol% of ErF3. The emission intensity at 550 nm in a constant ErF3 content (5 mol%) increased remarkably with the addition of YbF3 and was maximized around 7 mol% of YbF3 content, giving an increased ratio of about 200% of the initial value. The reason for the enhancement is discussed and it is derived mainly from two‐step excitation of Er3+ assisted by Yb3+ excited through the energy transfer from Er3+.