Jason Watson

Cooperative upconversion and energy transfer of new high Er 3+ - and Yb 3+ –Er 3+ -doped phosphate glasses

Systematic studies of cooperative upconversion and Yb3+–Er3+ energy transfer in newly developed phosphate glasses were performed by a rate-equation formalism. The cooperative-upconversion coefficients of the xa04I13/2 level for different Er3+ concentrations were determined from the luminescence-decay curves for high pump intensities. A small cooperative-upconversion coefficient of 1.1×10-18xa0cm3/s was obtained for a high Er3+ concentration of 4×1020u2002ions/cm3.Yb3+–Er3+ energy-transfer coefficients for an Er3+ concentration of 2×1020u2002ions/cm3 codoped with different Yb3+ concentrations were calculated from the lifetime measurements of the xa02F5/2 level of Yb3+u2002ions. For Er3+ codoped with an Yb3+ concentration of 6×1020u2002ions/cm3, an energy-transfer coefficient of 1.1×10-16xa0cm3/s and an energy-transfer efficiency higher than 95% were determined from our measurements under weak excitation. The cooperative-upconversion coefficients of Yb3+–Er3+-doped samples were found to be consistent with that of an Er3+-doped sample with the same Er3+ concentration. The weak cooperative-upconversion effect of high Er3+ concentrations and efficient Yb3+–Er3+ energy transfer indicate that these newly developed Er3+-u2002and Yb3+–Er3+-doped phosphate glasses are excellent for active device applications.

Effect of relative alkali content on absorption linewidth in erbium-doped tellurite glasses

Er 3+ doped tellurite glasses with various Na 2 O/Li 2 O, Na 2 O/K 2 O and K 2 O/Li 2 O ratios (0-4.5) were prepared at 850°C using a platinum crucible. The effect of relative alkali content on absorption linewidth in erbium-doped tellurite glasses was investigated. The highest effective linewidth was obtained from glass samples with mixed alkali molar ratio of Na 2 O/Li 2 O=1, Na 2 O/K 2 O=1 and K 2 O/Li 2 O=1. Glass transition temperature, crystallization temperature, density, refractive index, Judd-Ofelt parameters and emission cross-section of Er 3+ doped tellurite glasses are also reported.

Characterization of cooperative upconversion and energy transfer of Er3+ and Yb3+/Er3+ doped phosphate glasses

Cooperative upconversion and Yb3+-Er3+ energy transfer in newly developed phosphate glasses were studied in this paper. The cooperative upconversion coefficients of 4I13/2 level for different Er3+ concentrations were deduced from the pump intensity- dependent luminescence decay curves. Yb3+-Er3+ energy transfer efficiencies for different Yb3+ concentrations codoped with Er3+ (approximately 2 X 1020 ions/cm3) were estimated from the lifetime measurements of 2F5/2 level of Yb3+ ions. The small cooperative upconversion coefficients and high Yb3+-Er3+ energy transfer efficiencies indicate these newly developed Er3+ and Yb3+/Er3+ doped phosphate glasses are excellent for amplifier and laser applications.

Incorporation of triethoxysilyl functionalized Coumarin 4 in sol-gel hosts

A silylated Coumarin 4 (derCoum) laser dye has been incorporated over a large range of concentrations in sol-gel silica composites. Optically transparent films of derCoum and Coumarin 4 (Coum) doped silica were obtained; and their absorption and fluorescence spectra and fluorescence efficiency were measured. Dye extraction was investigated as a function of sol-gel processing conditions. Dye extraction results indicated that prehydrolysis of the derCoum and full hydrolysis of TMOS resulted in films from which the dye could not be extracted, suggesting that all the dye is bonded within the sol-gel matrix. The silylated dye films showed higher fluorescence efficiency at all concentrations with respect to the normal dye film.

Erbium-doped tellurite glasses for 1.5-um broadband amplification

Er

Raman shifting in the absence of multiple Stokes orders with a Nd:YAG laser in hydrogen: evidence of coupling between the forward and backward Stokes processes

3+) doped tellurite glasses with various Na2O/Li2O, Na2O/K2O and K2O/Li2O ratios were prepared. Absorption and emission spectra, glass transition temperatures, crystallization temperatures, densities, and refractive index of these glass samples were characterized. For all studied glass samples, the highest effective linewidth was obtained with mixed alkali molar ratio of Na2O/Li2O equals 1, Na2O/K2O equals 1 and K2O/Li2O equals 1. The studied glasses have a (Tx- Tg) exceeding 100 degree(s)C, indicating these glass samples are stable against devitrification. In addition, Judd-Ofelt analysis of several glasses was also performed.

Raman shifting in the absence of multiple Stokes orders with a 1.3-um Nd:YAG laser in hydrogen

By Raman shifting the output of a 1.319-/spl mu/m Nd:YAG laser in hydrogen, up to 24.5 mJ of Stokes light at 2.918 /spl mu/m has been generated. Due to the low energy of the 2.918-/spl mu/m Stokes photons, the first Stokes is the only Stokes line for this system. The effect of pressure on the conversion is notably simpler in this regime, but the gain saturates unusually slowly. An unexpected pump linewidth sensitivity in the forward Stokes conversion is observed. Coupling of the forward and backward Stokes processes is suggested as an explanation for these effects and is supported by a simple model.

Silylated Coumarin Dyes in Sol-Gel Hosts. 1. Structure and Environmental Factors on Fluorescent Properties

A Q-switched Nd:YAG laser generating 160 mJ in 60 ns at 1.3 micrometers has been shifted to 2.9 micrometers by Raman conversion in hydrogen. The energy of the 2.9 micrometers photons is insufficient to undergo further Stokes shifts. Thus the first Stokes line is the terminal wavelength for this process. While terminal Stokes components have been reached in previous Raman shifting studies, these components have always been the result of multiple Stokes shifts. In a single pass configuration photon conversion of up to 0.37 was realized. Conversion into anti-Stokes lines of up to third order was observed, albeit at insignificant energies. With the addition of an unoptimized resonator the photon conversion rose to 0.49. The pressure dependence of Stokes conversion was also investigated. The data show a smooth increase in output followed by saturation. This is in accordance with conversion into a single terminal Stokes lines. However, in contradiction with theory, the pump linewidth was observed to matter a great deal. Amplified elastic or near elastic scattering is suggested as an explanation for this result. Overall, the success of this work bodes well for forthcoming attempts to obtain tunable mid-IR radiation by means of a terminal first Stokes shift.