982 resultados para Tm^3


Relevância:

30.00% 30.00%

Publicador:

Resumo:

The thermal stability, 2 &mu;m fluorescence properties and energy transfer mechanism in Ho<sup>3+</sup> doped fluorophosphate glass sensitized by Yb<sup>3+</sup> and Tm<sup>3+</sup> were investigated. The characteristic temperatures, absorption spectrum and fluorescence spectrum of the glass sample were measured. &Delta;T calculated from the characteristic temperatures shows that the thermal stability of fluorophosphate glass is better than fluoride glass. According to the absorption spectrum, several spectroscopic parameters of the glass sample, such as Judd-Ofelt parameters and spontaneous transition probability were calculated and compared with other glass hosts. The largest spontaneous transition probability for Ho<sup>3+</sup>:<sup>5</sup> I<inf>7</inf>&rarr<sup>5</sup>I<inf>8</inf> transition in fluorophosphate glass which is 78.48 s<sup>-1</sup> indicates that fluorophosphate glass is an appropriate base glass to achieve 2 m fluorescence. From the fluorescence spectrum of the glass sample, the extremely strong 2.0 &mu;m fluorescence intensity is observed, which is higher than the intensity of 1.8 &mu;m fluorescence, showing that Ho<sup>3+</sup> ions sensitized by Yb<sup>3+</sup> and Tm<sup>3+</sup> is efficient. Meanwhile, the absorption sections and emission sections of Yb<sup>3+</sup>, Tm<sup>3+</sup> and Ho<sup>3+</sup> were calculated and the pumping scheme and energy transfer mechanism among Yb<sup>3+</sup>, Tm<sup>3+</sup> and Ho<sup>3+</sup> are discussed. The study indicates that Yb-Tm-Ho tri-doped fluorophosphate glass is a significant sensitization glass system under 980 nm excitation for 2 &mu;m applications.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The effect of Al(PO3)(3) content on physical, chemical and optical properties of fluorophosphate glasses for 2 mu m application, such as thermal stability, chemical durability, surface hardness, absorption spectra and emission spectra, is investigated. With the increment of Al(PO3)(3) content, the thermal stability characterized by the gap of T-g and T,, increases first and then decreases, and reaches the maximum level containing 5 mol% Al(PO3)(3) content. The density and chemical durability decrease monotonously with the introduction of Al(PO3)(3) content increasing, while the refractive index and surface hardness increase. Above properties of fluorophosphate glasses are also compared with fluoride glasses and phosphate glasses. The Judd-Ofelt parameters, absorption and emission cross sections are discussed based on the absorption spectra of Tm-doped glasses. The emission spectra are also measured and the 1.8 mu m fluorescence of the sample is obvious indicating that it is suitable to 2 mu m application. (c) 2008 Elsevier B.V. All rights reserved.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Absorption spectrum from 400 to 2000 run and upconversion fluorescence spectra under 940 nm pumping of YAG single crystal codoped with 5 at.% Yb3+ and 4 at.% Tm3+ were studied at room temperature. The blue upconversion emission centered at 483 nm corresponds to the transition (1)G(4) -> H-3(6), the emission band around 646 nm corresponds to the transition (1)G(4) -> F-3(4) of Tm3+. Energy transfer from Yb3+ to Tm3+ is mainly nonradiative and the transfer efficiency was experimentally assessed. The line strengths, transition probabilities and radiative lifetimes of (1)G(4) level were calculated by using Judd-Ofelt theory. Gain coefficient calculated from spectra shows that the upconversion corresponding with transitions (1)G(4) -> H-3(6) in YAG doped with Yb3+ and Tm3+ is potentially useful for blue light Output. (c) 2006 Elsevier B.V. All rights reserved.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Single-frequency output power of 7.3 W at 2.09 mu m from a monolithic Ho:YAG nonplanar ring oscillator (NPRO) is demonstrated. Resonantly pumped by a Tm-doped fiber laser at 1.91 mu m, the Ho:YAG NPRO produces 71% of slope efficiency with respect to absorbed pump power and nearly diffraction-limited output with a beam quality parameter of M-2 approximate to 1.1. (c) 2008 Optical Society of America

Relevância:

30.00% 30.00%

Publicador:

Resumo:

We report the continuous-wave and acousto-optical Q-switched operation of a diode-end-pumped Tm:YAP laser. Continuous-wave output power of 3.5 W at 1.99 mu m was obtained under the absorbed pump power of 14 W. Under Q-switched laser operation, the average output power increased from 1.57 W to 2.0 W, with an absorbed pump power of 12.6 W, as the repetition rate increased from 1 kHz to 10 kHz. The maximum Q-switched pulse energy was 1.57 mJ with a repetition rate of 1 kHz. The minimum pulse width was measured to be about 80 ns, corresponding to a peak power of 19.6 kW.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

(Czochralski)(TmLu2SiO5,TmLSO);LSO;-(Judd-Ofelt)TmLSO-.TmLSO2=9.135510-20cm2,4=8.410310-20cm2,6=1.590810-20cm2;TmLSO1.9m(3F43H6),2.03 ms,5.8110-18cm2,(FWHM)250 nm.TmLSO77 K.792 nm(LD),1960 nm,2.13 kW/cm2.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

We demonstrated continuous-wave ( CW) and Q-switched operation of a room-temperature Ho: YAlO3 laser that is resonantly end-pumped by a diode-pumped Tm: YLF laser at 1.91 mu m. The CW Ho: YAlO3 laser generated 5.5 W of linearly polarized (E parallel to c) output at 2118 nm with beam quality factor of M-2 approximate to 1.1 for an incident pump power of 13.8 W, corresponding to optical-to-optical conversion efficiency of 40%. Up to 1-mJ energy per pulse at pulse repetition frequency (PRF) of 5 kHz, and the maximum average power of 5.3-W with FWHM pulse duration of 30.5 ns at 20 kHz were achieved in Q-switched mode. (C) 2008 Optical Society of America.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

We reported on a diode end-pumped AO Q-switched Tm:YAP laser at 1937 nm. The average output power was 3.9 W, with a slope efficiency of 29.4% and optical-optical conversion efficiency of 21.6% at a 5-kHz repetition rate. The temperature dependency of the output power and the pulse width at different repetition rates were investigated in details.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The Ho:YAP crystal is grown by the Czochralski technique. The room-temperature polarized absorption spectra of Ho:YAP crystal was measured on a c-cut sample with 1 at% holmium. According to the obtained Judd-Ofelt intensity parameters Omega(2) = 1.42 x 10(-20) cm(2), Omega(4) = 2.92 x 10(-20) cm(2), and Omega(6) = 1.71 x 10(-20) cm(2), this paper calculated the fluorescence lifetime to be 6 ms for I-5(7) -> I-5(8) transition, and the integrated emission cross section to be 2.24 x 10(-18) cm(2). It investigates the room-temperature Ho:YAP laser end-pumped by a 1.91-mu m Tm:YLF laser. The maximum output power was 4.1 W when the incident 1.91-mu m pump power was 14.4W. The slope efficiency is 40.8%, corresponding to an optical-to-optical conversion efficiency of 28.4%. The Ho:YAP output wavelength was centred at 2118 nm with full width at half maximum of about 0.8 nm.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

O cncer colorretal (CCR) o terceiro tipo de cncer mais incidente no mundo para o sexo masculino, o segundo para o sexo feminino e a radioterapia um dos tratamentos de primeira linha no combate a este tipo de cncer. Durante a progresso do CCR as clulas sofrem alteraes morfogenticas, sendo a desorganizao do complexo juncional apical (CJA) um dos eventos iniciais desse processo. As junes oclusivas (JTs) so um dos principais componentes da CJA e desempenham papel importante no controle do fluxo paracelular, na determinao da polaridade celular e na transduo de sinais relacionados com a progresso tumoral. As claudinas so protenas transmembrana, constituintes das JTs e cumprem um importante papel no controle desses eventos. Alteraes na expresso das claudinas so observadas em tumores de diferentes rgos e tm sido relacionadas com a progresso tumoral. No entanto os mecanismos que regulam essas alteraes e sua consequncia na progresso do CCR so poucos conhecidos. Desta forma, o presente estudo teve como objetivo avaliar a influncia da superexpresso da claudina-3 na radiorresposta de clulas CCR. Nossos resultados mostraram que a superexpresso de claudina-3 minimiza alteraes morfolgicas causadas pela radiao, causa diminuio da resistncia eltrica transepitelial e no tem efeito na permeabilidade a macromolculas aps a irradiao. Alm disso, observamos que a superexpresso de claudina-3 aumenta o potencial proliferativo das clulas e que esta caracterstica torna as clulas mais sensveis a radiao. Porm quando avaliamos eventos celulares relacionados a progresso tumoral observamos que apesar da radiao diminuir a capacidade migratria das prognies, as clulas que superexpressam claudina-3 apresentam migrao mais elevada. Alm disso, verificamos que a superexpresso de claudina-3 diminui a invaso e a capacidade de formao de colnias frente ao tratamento com a radiao. Em seguida fomos avaliar o efeito da inibio das vias de proliferao (MEK/ERK) e sobrevivncia (PI3K-Akt) na resposta das clulas que superexpressam claudina-3 frente a radiao. Observamos que a inibio de MEK capaz de sensibilizar as clulas que superexpressam claudina-3 radiao no ensaio de proliferao celular, no entanto a inibio de MEK e PI3K antes da exposio radiao capaz aumentar a migrao e a capacidade de formao de colnias de clulas que superexpressam claudina-3 contribuindo para o aumento do potencial maligno. Em conjunto nossos resultados mostram que a superexpresso de claudina-3 contribui para um fentipo mais maligno, no entanto frente ao tratamento com a radiao capaz de sensibilizar as clulas.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

NDVI PCA123-GHI 62GHIGHI TMGHINDVIGHINDVIGHIGHITM

Relevância:

30.00% 30.00%

Publicador:

Resumo:

We demonstrate mode-locking of a thulium-doped fiber laser operating at 1.94 m, using a graphene-polymer based saturable absorber. The laser outputs 3.6 ps pulses, with 0.4 nJ energy and an amplitude fluctuation 0.5%, at 6.46 MHz. This is a simple, low-cost, stable and convenient laser oscillator for applications where eye-safe and low-photon-energy light sources are required, such as sensing and biomedical diagnostics. 2012 Optical Society of America.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The characteristics of whispering-gallery modes (WGMs) in 3-D cylindrical, square, and triangular microcavities with vertical optical confinement of semiconductors are numerically investigated by the finite-difference time-domain (FDTD) technique. For a microcylinder with a vertical refractive index 3.17/3.4/3.17 and a center layer thickness 0.2 mu m, Q-factors of transverse electric (TE) WGMs around wavelength 1550 nm are smaller than 10(3), as the radius R < 4 mu m and reach the orders of 10(4) and 10(6) as R = 5 and 6 mu m, respectively. However, the Q-factor of transverse magnetic (TM) WGMs at wavelength 1.659 mu m reaches 7.5 x 10(5) as R = 1 mu m. The mode coupling between the WGMs and vertical radiation modes in the cladding layer results in vertical radiation loss for the WGMs. In the microcylinder, the mode wavelength of TM WGM is larger than the cutoff wavelength of the vertical radiation mode with the same mode numbers, so TM WGMs cannot couple with the vertical radiation mode and have high Q-factor. In contrast, TE WGMs can couple with the corresponding vertical radiation mode in the 3-D microcylinder as R < 5 mu m. However, the mode wavelength of the TE WGM approaches (is larger than) the cutoff wavelength of the corresponding radiation modes at R = 5 mu m (6 mu m), so TE WGMs have high Q-factors in such microcylinders too. The results show that a critical lateral size is required for obtaining high, Q-factor TE WGMs in the 3-D microcylinder. For 3-D square and triangular microcavities, we also find that the Q-factor of TM WGM is larger than that of TE WGM.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The vertical radiation loss of three-dimensional (3-D) microresonators is investigated by 3-D finite-difference time-domain (FDTD) simulation. The simulation shows that the vertical radiation causes an important loss in the microresonators with weak waveguiding, and result in decrease of the quality factors (Q-factors) of whispering-gallery (WG) modes. Through the simulation, we find that TM-like modes have much weaker vertical radiation loss than TE-like modes. High Q-factor TM-like modes are observed in the 3-D microresonators with weak vertical waveguiding, but the Q-factors of TE-like modes decrease greatly.