Temperature Dependence Of Efficiency Research Articles

Temperature dependence of efficiency and thermal lensing of diode-laser-pumped Nd:YAG lasers

Efficiencies, lasing thresholds and thermal lensing of a Nd:YAG rod side-pumped with two 10 W diode-laser-arrays are measured for various rod temperatures between 80 K and 380 K. The threshold is reduced by a factor of 2.5–4 on cooling from room temperature to about 100 K, while the slope efficiency is increased by between 0% and 50% depending on the reflectivity of the outcoupling mirror. Extrapolation to a 240 W pumped laser gives an increase in optical efficiency of 25% to 30%. The thermal lensing measured with a beam deflection and an interferometric method is reduced by a factor of 10.

Persistent photoconductivity in insulating and superconducting YBa2Cu3Ox thin films: Temperature and spectral dependence.

Temperature and spectral dependencies of photoinduced changes of resistance in YBa[sub 2]Cu[sub 3]O[sub [ital x]] thin films with oxygen content ranging as 6.35[lt][ital x][lt]6.75 were measured on both sides of the metal-insulator transition (MIT). The absolute value of efficiency of initiation of photoinduced changes decreases with an increase of oxygen content, but the position of peaks in the spectral dependence does not change with a change of [ital x]. Temperature dependencies of efficiency have an anomaly at [ital T][similar to]220 K, which is present in all the samples studied and correlates with anomalies observed by other experimental techniques. Qualitatively similar temperature and spectral dependencies of efficiency for the samples in both the insulating and metallic phases may be considered as an indication that the persistent photoconductivity effect in Y-Ba-Cu-O on both sides of the MIT has a common origin.

The first magnetic penetration field in BSCCO single crystals, temperature dependence and electron irradiation effect

We report measurements of the first magnetic penetration field, H p, of Bi 2.2 Sr 1.89 CaCu 2 O 8+ ϖ crystals by a novel local Hall probe technique. We demonstrate that H p is slightly enhanced above the thermodynamic lower critical field, H c1, by the Bean-Livingston surface barrier, and that irreversible magnetization at temperatures between 50K and T c (87.8K) arises mainly from the presence of this barrier. We argue that the non-linear temperature variation of H p observed, results from a temperature-dependent efficiency of the Bean-Livingston barrier.

D - A recombination luminescence in (Zn, Cd)S DCEL powder cells

DCEL powder cells containing ZnS:Cl or (Zn, CdS)Ag, Cl phosphors exhibit D - A recombination luminescence when excited by unipolar pulses. The emission follows and preceeds the voltage pulse and arises from the detrapping of electrons created by the avalanche process. From the temperature dependence of efficiency and thermoluminescence, electron trap depths of 0.36 and 0.41 eV were deduced for ZnS:Cl and ZnS:Ag respectively. The efficiency of recombination can be increased by following the ionisation pulse with a pulse of lower amplitude but opposite polarity. Power efficiencies of 0.005% (blue), 0.008% (green) and 0.001% (orange) were found for (Zn, Cd)S Ag phosphors.

Temperature dependence of F-centre accumulation efficiency in doped alkali halides

A model explaining the temperature dependence of the efficiency of F-centre accumulation (as well as F2-centre destruction), observed in the course of steady-state experiments, has been developed. The model takes into account three- (or one-) dimensional continuous diffusion of H centres, resulting in a primary process, and their decay due to the diffusion-controlled: (i) annihilation, (ii) tunnelling recombination with F centres and (iii) localization by pre-existing defects (or recombination with F2 centres).