Oscillator Strength Of Absorption Transition Research Articles

Nano cristobalite embedded Er3+ doped multi-functional silica phosphate composite glasses for optoelectronic applications

Composite silica-based glasses were synthesized with varying concentrations of Er3+ by sol-gel route. The presence of alkali sodium ions reoriented the silica tetrahedra, eventually forming the cristobalite phase in the glasses. The addition of Er3+ reduces the crystallite size from 23.8 nm to 6.9 nm, while retaining the fractional ceramic attribute for effectuating mechanical stability and ductility. Band gap energy increases with Er3+ doping by the principles of the Burstein-Moss shift, increasing transmittance to 90% in the glasses. The density of the glasses increases with erbium content, with a subsequent increase in ionic bonding as validated by the metallization criterion. Judd OFelt (JO) parameters were evaluated from the oscillator strengths of absorption transitions, identifying decreasing covalency in the glass systems. Broad bandwidth and lifetime of 79.9 nm and 6.2 ms respectively were obtained for near-infrared (NIR) transmission at 1.47 μm, suitable for an S-band telecommunication window. The material has potential red lasing performance corresponding to the transition: 4F9/2→4I15/2. Low dielectric constants and decreasing activation energy of the glass material at higher frequencies, as derived from Arrhenius plots, is suggestive of a cost-effective inter-layer dielectric substrate for microwave signal propagation. This could be favorably capitalized for micro-fabrication in integrated electronic industries, employing the Low-Temperature Co-fired Ceramic (LTCC) technology as a strategic alternative to the ceramic substrates devised otherwise using high sintering temperatures.

Laser heating of the Y_1-xDy_xPO_4 nanocrystals

We propose a novel material prepared by microwave-hydrothermal treatment, the tetragonal xenotime-type yttrium orthophosphate YPO4 nanocrystals doped by different concentrations of Dy3+. It may be suitable for laser-induced local heating of cancer tumors for hyperthermia. We heated a powder consisted of the nanoparticles by focused quasi-CW laser irradiation at different wavelengths in the near IR spectral range fitting the transparency window of biological tissues. The local temperature on the surface of the powder in the place of irradiation increases linearly with increasing laser power and increasing the Dy3+ concentration. At the same time the efficiency of local heating Φ = ΔT / (P f) (ΔT is a local temperature increase, f is an oscillator strength of absorption transition, and P is the quantity of laser power) is proportional to the energy of the initially excited electronic level. The proposed method allows for high rates of heating and cooling. The laser power used for heating was rather low, tens of milliwatts that together with short heating time to required temperature may result in extremely low doses of laser irradiation for heating.

Oscillator strengths of absorption transitions from the 5 D 0 state in huntite-like EuAl3(BO3)4 polycrystals

Oscillator strengths of absorption transitions from the metastable 5 D 0 state of Eu3+ ions in aluminoborate polycrystals with the huntite structure were determined using crystal-field theory. It was established that the oscillator strength of the 5 D 0 → 5 F 4 transition, which was resonant with the 5 D 0 → 7 F 2 transition, was many times greater than that for other resonant transitions of Eu3+ ions. The transition 5 D 0 → 5 H 6 had the minimum oscillator strength among such resonant absorption transitions.

Yb^3+ ion concentration effects on ∼1 μm emission in tellurite glass

The effects of Yb3+ ion concentration on physical, optical, and spectroscopic properties have been studied in a low phonon (∼590 cm−1) barium-lanthanum-tellurite glass. Due to the unfeasibility of Judd-Ofelt theory Yb3+-doped systems, the oscillator strength of absorption transition, F27/2→F5/22 has been evaluated by using the Smakula equation. The nature of emission from F25/2→F7/22 transition of Yb3+ ions is described theoretically by using a rate equation in comparison with experimental results. By applying reciprocity (RM) and Fuchtbauer-Ladenburg methods on emission spectra as well as the excitation random walk model on measured fluorescence lifetimes, the radiation trapping and concentration quenching effects have been discussed. Considering all the spectroscopic and laser performance parameters, an optimum Yb-ion doping concentration (YT1) has been determined, and the gain measurements performed on the sample revealed a flat gain over a broad wavelength range could be achieved even with a low (∼20%) excitation population density. A comparative study with other hosts revealed the potentiality of the present glass for ∼1 micron emission.

Self-consistent description of the Stark structure of multiplets and intensities of absorption transitions in Pr3+ ions in Y3Al5O12

The Stark structure of multiplets and the oscillator strengths of absorption transitions in Pr3+ ions in a Y3Al5O12 crystal have been described with allowance for the effect of the excited opposite-parity configuration and the charge-transfer configuration. To take into account this effect, a modified crystal-field Hamiltonian and an effective line-strength operator for intermultiplet electric-dipole transitions are proposed. Their use in description of experimental data makes it possible to decrease the standard deviation by 37 and 20%, respectively, in comparison with the standard theories. The even-and odd-crystal-field parameters and the covalence parameters have been obtained from the description of Stark levels. The intensity parameters calculated on the basis of the covalence parameters and odd-crystal-field parameters are in satisfactory agreement with the parameters obtained from the description of the experimental oscillator strengths.