Linear polarization output performance of Nd:YAG laser at 946 nm considering the energy-transfer upconversion

A theoretical model of quasi-three-level laser system is developed, in which both the thermally induced depolarization loss and the effect of energy-transfer upconversion are taken into account. Based on the theoretical investigation of the influences of output transmission and incident pump power on thermally induced depolarization loss, the output performance of 946 nm linearly polarized Nd：YAG laser is experimentally studied. By optimizing the transmission of output coupler, a 946 nm linearly polarized continuous-wave single-transverse-mode laser with an output power of 4.2 W and an optical-optical conversion efficiency of 16.8% is obtained, and the measured beam quality factors are M2 = 1.13 and My2 = 1.21. The theoretical prediction is in good agreement with the experimental result.

Energy-transfer Process Accelerated by the Formation of Electrostatically Stabilized Aggregate (ESAg)

The energy-transfer process between sodium (omega-[2-(alpha -naphthyl)ethoxy]undecanoate (FP-)* and sodium omega -9-anthrylmethyl glutarate (AFP(-)) is accelerated by the formation of ESAg when cetyltrimethylammonium chloride (S16(+)) has been added to the solvent system of FP-* and AFP(-). This result is yet another evidence for the formation of ESAg.

CHARGE-TRANSFER AND ENERGY-TRANSFER IN THE PHOTO-INDUCED COPOLYMERIZATION OF 2-VINYLNAPHTHALENE WITH MALEIC ANHYDRIDE

The initiation mechanism of the copolymerization of 2-vinylnaphthalene with maleic anhydride was studied under irradiation of 365 nm. The excited complex was formed from (1) the local excitation of 2-vinylnaphthalene followed by the charge-transfer interaction with maleic anhydride and (2) the excitation of the ground state charge-transfer complex, and then it collapsed to 1,4-tetramethylene biradical for initiation. A1: 1 alternating copolymer was formed in different monomer feeds. Addition of benzophenone could greatly enhance the rate of copolymerization through energy-transfer mechanism.

Near Infrared Photoluminescence from Yb,Al Co-implanted SiO2 Films on Silicon

Intense room-temperature near infrared （NIR） photoluminescence （980 nm and 1032 nm） is observed from Yb,Al co-implanted SiO2 films on silicon. The optical transitions occur between the ^2F5/2 and ^2F7/2 levels of Yb^3＋ in SiO2. The additional Al-implantation into SiO2 films can effectively improve the concentration quenching effect of Yb^3＋ in SiO2. Photoluminescence excitation spectroscopy shows that the NIR photoluminescence is due to the non-radiative energy transfer from Al-implantation-induced non-bridging oxygen hole defects in SiO2 to Yb^3＋ in the Yb-related luminescent complexes. It is believed that the defect-mediated luminescence of rare-earth ions in SiO2 is very effective.

Fast Optical Switching Using Oriented Cyanine Dye-Doped Nematic Liquid Crystal

A cyanine dye, 2-[7-（1,3-dihydro-1,3,3-trimethyl-2H-indol-2-ylidene）-1,3,5-heptatrienyl]-1,3,3-trimethyl-3H-indolium iodide （NK-125）, is doped in 4-cyano-4＇-pentylbiphenyl （5 CB）, and the mixture is sandwiched between two pieces of rubbed glass plates. The third-order nonlinear optical properties of the oriented NK-125-SCB layers are measured by the resonant femtosecond degenerate four-wave mixing （DFWM） technique at 760 nm. The third-order nonlinear optical susceptibility of one of the present samples is 5.5×10^-8 esu. The slow DFWM response of the NK-125-SCB layers due to a population grating is accelerated by the increasing laser power because of amplified spontaneous emission （ASE）. On the other hand, we do not observe a similar phenomenon for NK-125- polyethylene glycol （PEG-400）. Oriented NK-125 molecules in nematic liquid crystals must have very high ASE efficiency. Hence the population grating in a DFWM signal disappears within about 4 ps. It is expected that NK-125-SCB can be used as a material for very fast all-optical switching.

Electroluminescence of a Multi-Layered Organic Light-Emitting Diode Utilizing Trans-4- [p-[N-met hyl-N- （hydroxymet hyl） amino] styryl]-N-Methylphridinium Tetraphenylborate as the Active Layer

Employing an organic dye salt of trans-4-[p-[N-methyl-N-（hydroxymethyl）amino]styryl]-N-methylphridinium tetraphenylbovate （ASPT） as the active layer, 8-hydrocyquinoline aluminium （Alq3） as the electron transporting layer and N, N＇-diphenyl-N, N＇-bis（3-methylphenyl）-[1,1＇-biphenyl]-4,4＇-diamine （TPD） as the hole transporting layer, respectively, we fabricate a multi-layered organic light-emitting diode and observe the colour tunable electroluminescence （EL）. The dependence of the EL spectra on the applied voltage is investigated in detail, and the recombination mechanism is discussed by considering the variation of the hole-electron recombination region.

Improved Fluorescence from Tm^3＋/Er^3＋/Ce^3＋ Triply Doped Bismuth-Silicate Glasses for S＋C-bands Amplifiers

Fluorescence of Tm^3＋/Er^3＋ codoped bismuth-silica （BS） glasses and the sensitization of Ce^3＋ are investigated, It shows that Ce^3＋ codoping with Tm^3＋/Er^3＋ in BS glasses results in a quenching of Tm^3＋ ion emission from ^3F4 to the ^3H6 level. Consequently, the 1.47μm emission occurs after the population inversion between the ^3H4 and ^3F4 levels. Furthermore, the codoped glasses show the broad emission spectra over the whole S and C bands with full-width at half-maximum （FWHM） up to about 119nm, as it combines 1.55μm emission band of Er^3＋ with 1.47μm emission band of Tm^3＋ under 800hm excitation.

Optical Properties of Pr^3＋-Doped Y2SiO5 Crystals

Optical properties of Pr^3＋ doped in Y2SiO5, including absorption spectra, emission spectra, and fluorescence decay, have been investigated with a special attention in the UV region. Broad band （270-350nm） UV fluorescence assigned to the transitions 4f5d → 4f^2 ^3Hj, ^3Fj is found. The spontaneous transition probabilities in the 4f^2 intraconfiguration are calculated by utilizing the 3udd-Ofelt theory, by which three phenomenological parameters （Ω2, Ω4, Ω6,） are obtained by fitting the absorption spectra. For the evaluation of transition probability of the interconfiguration 4f5d → 4f^2, a formula for electric dipole transition is employed. In comparison of the measured fluorescence lifetime with the calculated spontaneous radiative lifetime, the fluorescence quantum efficiency is deduced.

Influence of Dopant Concentration on Electroluminescent Performance of Organic White-Light-Emitting Device with Double-Emissive-Layered Structure

A novel phosphorescent organic white-light-emitting device （WOLED） with contiguration of ITO/NPB/CBP： TBPe：rubrene/Zn（BTZ）2：Ir（piq）2（acac）/Zn（BTZ）2/Mg：Ag is fabricated successfully, where the phosphorescent dye bis （1-（phenyl）isoquinoline） iridium （Ⅲ） acetylanetonate （Ir（piq）2 （acac）） doped into bis-（2-（2-hydroxyphenyl） benzothiazole）zinc （Zn（BTZ）2） （greenish-blue emitting material with electron transport character） as the red emitting layer, and fluorescent dye 2,5,8,11-tetra-tertbutylperylene （TBPe） and 5,6,11,12-tetraphenyl-naphthacene （rubrene） together doped into 4,4＇-N,N＇-dicarbazole-biphenyl （CBP） （ambipolar conductivity material） as the blue-orange emitting layer, respectively. The two emitting layers are sandwiched between the hole-transport layer N ,N＇-biphenyl-N , N＇-bis （1-naph thyl）-（1,1＇-biphenyl）-4, 4 Cdiamine （NP B） and electron-transport layer （Zn（BTZ）2 ） The optimum device turns on at the driving voltage of 4.5 V. A maximum external quantum efficiency of 1.53%. and brightness 15000 cd/m^2 are presented. The best point of the Commission Internationale de 1＇Eclairage （CIE） coordinates locates at （0.335, 0.338） at about 13 V. Moreover, we also discuss how to achieve the bright pure white light through optimizing the doping concentration of each dye from the viewpoint of energy transfer process.

Enhanced Electroluminescent Efficiency Based on Functionalized Europium Complexes in Polymer Light-Emitting Diodes

Efficient red polymer light-emitting diodes are fabricated with the single active layer from the blends of poly（N- vinylcarbazole） （PVK） in the presence of 30 wt. % electron-transporting compound 2-（4-biphenylyl）-5-（ptert- butylphenyl）-1,3,4-oxadiazole （PBD） and europium complexes. The polyphenylene functionalized europium com- plex shows an enhanced electroluminescent efficiency due to the large site-isolation effect. For the polyphenylene functionalized europium complex, the maximum external quantum efficiency of 1.90% and luminous efficiency of 2.01 cd A^-1 are achieved with emission peak at 612nm. The maximum brightness is more than 300cd m^-2.

Miscibility and Molecular Orientation of Carbazole in Mixed Langmuir and Langmuir-Blodgett Films

We report the miscibility and molecular orientation of carbazole （CA） molecules in the mixed Langmuir and Langmuir-Blodgett （LB） films of CA in polymethyl methacrylate （PMMA） and stearic acid （SA） matrices. The lr-A isotherm confirms the formation of stable Langmuir films of CA mixed with either PMMA or SA at airwater interface. ＇Characteristics of area per molecule versus molefraction and collapse pressure versus molefraction reveal complete demixing of CA and the matrix PMMA/SA molecules in the mixed films. Absorption spectroscopy certainly confirms the fact that CA molecules have preferred orientation on the substrate of the LB films.

Interface formation energy,bonding,energy band alignment in α-NaYF4 related core shell models:For future multi-layer core shell luminescence materials

To break through the bottle-neck of quantum yield in upconversion （UC） core-shell system, we elucidated that the energy transfer efficiency in core-shell system had an evident contribution from the charge transfer of interface with related to two factors： （i） band offsets and （2） binding energy area density. These two variables were determined by material intrinsic properties and core-shell thickness ratio. We further unraveled the mechanism of non-radiative energy transfer by charge transfer induced dipole at the inter- face, based on a quasi-classical derivation from F6rster type resonant energy transfer （FRET） model. With stable bonding across the interface, the contributions on energy transfer in both radiative and non-radiative energy transfer should also be accounted together in Auzel＇s energy transfer （ETU） model in core-shell system. Based on the discussion about interface bonding, band offsets, and forma- tion energies, we figured out the significance of interface bonding induced gap states （IBIGS） that played a significant role for influ- encing the charge transfer and radiative type energy transfer. The interface band offsets were a key factor in dominating the non-radiative energy transfer, which was also correlated to core-shell thickness ratio. We found that the energy area density with re- lated to core/shell thickness ratio followed the trend of Boltzman sigmoidal growth function. By the physical trend, this work contrib- uted a reference how the multi-layered core-shell structure was formed starting from the very beginning within minimum size. A route was paved towards a systematic study of the interface to unveil the energy transfer mechanism in core-shell systems.