Effect of F- ions on emission cross-section and fluorescence lifetime of Yb3+-doped tellurite glasses

The effects of F- ions in Yb3+-doped tellurite glass systems on the emission cross-section and measured fluorescence lifetime are investigated. The results show that both the emission cross-section and the fluorescence lifetime of Yb3+ ions increase from 1.32 to 1.39 pm(2) and from 0.93 to 1.12 ms respectively with the increase of F- ions from 0 to 10 mol% and that such oxyfluoride tellurite glass system is a promising laser host matrix for high power generation. FT-IR spectra were used to analyze the effect of F- ions on the structure of tellurite glasses and the change of OH- groups in this glass system. Analysis demonstrates that the addition of fluoride decreases the symmetry of the structure of tellurite glasses resulting in increasing of the emission cross-section and removes the OH- groups resulting in increasing of the measured fluorescence lifetime of Yb3+ ions. (c) 2005 Elsevier B.V. All rights reserved.

Room-Temperature Continuous-Wave Operation of InGaN-Based Blue-Violet Laser Diodes with a Lifetime of 15.6 Hours

We report our recent progress of investigations on InGaN-based blue-violet laser diodes (LDs). The room-temperature (RT) cw operation lifetime of LDs has extended to longer than 15.6 h. The LD structure was grown on a c-plane free-standing (FS) GaN substrate by metal organic chemical vapor deposition (MOCVD). The typical threshold current and voltage of LD under RT cw operation are 78 mA and 6.8 V, respectively. The experimental analysis of degradation of LD performances suggests that after aging treatment, the increase of series resistance and threshold current can be mainly attributed to the deterioration of p-type ohmic contact and the decrease of internal quantum efficiency of multiple quantum well (MQW), respectively.

The effect of hyperfine interaction on the lifetime of the 3s3p P-3(2) level of Mg-like ions

On the basis of previous work, the hyperfine-induced 3s3p P-3(2) -> 3s(2) S-1(0) E1 transition probabilities of Mg-like ions were further calculated using the GRASP2K package based on the multiconfiguration Dirac-Hartree-Fock method. The contribution to the lifetime of the P-3(2) level from the 3s3p P-3(2) -> 3s(2) S-1(0) hyperfine-induced E1, 3s3p P-3(2) -> 3s3p P-3(1) M1, 3s3p P-3(2) -> 3s(2) S-1(0) M2 and 3s3p P-3(2) -> 3s3p P-3(0,1) E2 transition was discussed in detail. It was found that hyperfine interaction has an obvious effect on the lifetime at the beginning of the Mg-like isoelectronic sequence.

Study on the lifetime of M-intermediate of bacteriorhodopsin film chemically modified with CeO2 nanoparticles

The characteristics of intermediates of bacteriorhodopsin (bR) can be verified by chemical modification of its surroundings. CeO2 nanoparticles, which were obtained using water-in-oil (W/O) microemulsion and calcined at various temperatures, were used as chemical additive for the modification of bR. X-ray diffraction (XRD) shows that the mean particle sizes for the samples calcined at 500 and 800 degrees C are approximately 10 and 30 nm, respectively. We prepared CeO2 nanoparticle modified poly(vinyl alcohol) (bR-PVA) films with an optical density of about 1.5 at the ground state. It is observed that the lifetime of the Wintermediate for the modified films is prolonged compared with that of the unmodified ones, and the lifetime increases with decreasing particle size. A probable mechanism, which is likely to involve effective molecular interactions between the CeO2 nanoparticles and the bR molecules, is discussed. The hydroxyl groups, which might arise from the interaction between the nanoparticles and the surrounding water molecules, help to lower the ability of the Schiff base of uptaking protons in the Wintermediate. The results indicate that controlling the interactions between biomolecules and various nanomaterials would enlarge the functionality and the range of the application of nanoparticles.

Fluorescence lifetime increase by introduction of F- ions in ytterbium-doped TeO2-based glasses

this paper was retracted

Fabrication process and power and lifetime characteristics of very-small-aperture laser

High output power very-small-aperture laser has been created on 650 nm edge emitting laser diodes. The far-field output power is 0.4 mW at the 25 mA driving current, and the highest output power exceeds 1 mW. The special fabrication process is described and the failure mechanism leading to the short lifetime of the devices is discussed.

Broad-spectrum and long-lifetime emissions of Nd3+ ions in lead fluorosilicate glass

A novel Nd3+-doped lead fluorosilicate glass (NPS glass) is prepared by a two-step melting process. Based on the absorption spectrum a Judd-Ofelt theory analysis is made. The emission line width of NPS glass is 44.2nm. The fluorescence decay lifetime of the 4F3/2 level is 586±20μsec, and the stimulated emission cross-section is 0.87×10-20cm2 at 1056nm. A laser oscillation is occurred at 1062nm when pumped by 808nm Diode Laser. The slope efficiency is 23.7% with a 415mJ threshold. It is supposed that NPS glass is a good candidate for using in ultra-short pulse generation and amplification by the broad emission bandwidth and long fluorescence lifetime.

Long lifetime plasma channel in air generated by multiple femtosecond laser pulses and an external electrical field

The lifetime of a plasma channel produced by self-guiding intense femtosecond laser pulses in air is largely prolonged by adding a high voltage electrical field in the plasma and by introducing a series of femtosecond laser pulses. An optimal lifetime value is realized through adjusting the delay among these laser pulses. The lifetime of a plasma channel is greatly enhanced to 350 ns by using four sequential intense 100fs( FWHM) laser pulses with an external electrical field of about 350kV/m, which proves the feasibility of prolonging the lifetime of plasma by adding an external electrical field and employing multiple laser pulses. (c) 2006 Optical Society of America.

Infrared luminescence properties of bismuth-doped barium silicate glasses

Infrared (IR) luminescence covering 1.1 to similar to 1.6 mu m wavelength region was observed from bismuth-doped barium silicate glasses, excited by a laser diode at 808 nm wavelength region, at room temperature. The peak of the IR luminescence appears at 1325 nm. A full width half-maximum (FWHM) and the lifetime of the fluorescence is more than 200 nm and 400 mu s, respectively. The fluorescence intensity increases with Al2O3 content, but decreases with BaO content. We suggest that the IR luminescence should be ascribed to the low valence state of bismuth Bi2+ or Bi+, and Al3+ ions play an indirect dispersing role for the infrared luminescent centers.

Optical properties of transparent alkali gallium silicate glass-ceramics containing Ni2+-doped beta-Ga2O3 nanocrystals

Broadband near-infrared (IR) luminescence in transparent alkali gallium silicate glass-ceramics containing N2+-doped beta-Ga2O3 nanocrystals was observed. This broadband emission could be attributed to the T-3(2g) (F-3) -> (3)A(2g) (F-3) transition of octahedral Ni2+ ions in glass-ceramics. The full width at half-maximum (FWHM) of the near-IR luminescence and fluorescent lifetime of the glass-ceramic doped with 0.10 mol% NiO were 260 nm and similar to 1220 mu s, respectively. It is expected that transparent Ni2+-doped beta-Ga2O3 glass-ceramics with this broad near-IR emission and long fluorescent lifetime have potential applications as super-broadband optical amplification media.

Optical spectroscopy and energy transfer of Er3+/Ce3+ in B2O3-doped bismuth-silicate glasses

Ce3+ and B2O3 are introduced into erbium-doped Bi2O3-SiO2 glass to enhance the luminescence emission and optic spectra characters of Er3+. The energy transfer from Er3+ to Ce3+ will obviously be improved with the phonon energy increasing by the addition of B2O3. Here, the nonradiative rate, the lifetime of the I-4(11/2) -> I-4(3/2) transition, and the emission intensity and bandwidth of the 1.5 mu m luminescence with the I-4(13/2) -> I-4(5/2) transition of Er3+ are discussed in detail. The results show that the optical parameters of Er3+ in this bismuth-borate-silicate glass are nearly as good as that in tellurite glass, and the physical properties are similar to those in silicate glass. With the Judd-Ofelt and nonradiative theory analyses, the multiphonon decay and phonon-assisted energy-transfer (PAT) rates are calculated for the Er3+/Ce3+ codoped glasses. For the PAT process, an optimum value of the glass phonon energy is obtained after B2O3 is introduced into the Er3+/Ce3+ codoped bismuth-silicate glasses, and it much improves the energy-transfer rate between Er3+ I-4(11/2)-I-4(13/2) and Ce3+ F-2(5/2) -> F-2(7/2), although there is an energy mismatch. (c) 2007 Optical Society of America.

Effect of alkaline-earth metal composition on spectroscopic properties of Er3+ in fluorophosphate glasses

Optical spectroscopic properties of Er3+-doped alkaline-earth metal modified fluoropho sphate glasses have been investigated experimentally for developing broadband fiber and planar amplifiers. The results show a strong correlation between the alkaline-earth metal content and the spectroscopic parameters such as absorption and emission cross sections, full widths at half-maximum and Judd-Ofelt intensity parameters. It is found that strontium ions could have more influences on the Judd-Ofelt intensity parameters and the absorption and emission cross sections than other alkaline-earth metal ions such as Mg2+, Ca2+, Ba2+. The sample containing 23 mol% strontium fluoride exhibits the maximum emission cross section of 7.58 x 10(-21) cm(2), the broadest full width at half-maximum of 65 nm and the longer lifetime of 8.6 ms among the alkaline-earth metal modified fluorophosphates glasses studied. The Judd-Ofelt intensity parameter Omega(6)s, the emission cross sections and the full widths at half-maximum in the Er3+-doped fluorophosphate glasses studied are larger than in the silicate and phosphate glasses.

Spectroscopic properties of fluorophosphate glass with high Er(3+)supercript stop concentration

Fluorophosphate glass with 4 mol.% ErF3 content was prepared. The different scanning calorimetry was conducted. Raman spectrum, infrared transmission spectrum, absorption spectrum were measured. Fluorescence spectrum and lifetime of emission around 1.53 mu m were measured under 970 nm laser diode excitation. The metaphosphate content in the composition is limited, but the maximum phonon energy of glass amounts to 1290 cm- 1, and is comparatively high. The full width at half maximum is about 56 nm, and is wider than for most of the materials investigated. The measured lifetime of I-4(13/2) -> I-4(15/2) transition, contributed by the high phonon energy, inefficient interaction of Er3+ ions, and low water content, amounts to no less than 7.36 ms though the Er3+ concentration is high. This work might provide useful information for the development of compact optical devices.