共查询到20条相似文献,搜索用时 31 毫秒
1.
Pujol M.C. Massons J. Aguilo M. Diaz F. Rico M. Zaldo C. 《Quantum Electronics, IEEE Journal of》2002,38(1):93-100
The spectroscopic properties of Ho3+ laser channels in KGd(WO4)2 crystals have been investigated using optical absorption, photoluminescence, and lifetime measurements. The radiative lifetimes of Ho3+ have been calculated through a Judd-Ofelt (JO) formalism using 300-K optical absorption results. The JO parameters obtained were Ω2=15.35×10-20 cm2, Ω 4=3.79×10-20 cm2, Ω6 =1.69×10-20 cm2. The 7-300-K lifetimes obtained in diluted (8·1018 cm-3) KGW:0.1% Ho samples are: τ(5F3)≈0.9 μs, τ( 5S2)=19-3.6 μs, and τ(5F5 )≈1.1 μs. For Ho concentrations below 1.5×1020 cm-3, multiphonon emission is the main source of non radiative losses, and the temperature independent multiphonon probability in KGW is found to follow the energy gap law τph -1(0)=βexp(-αΔE), where β=1.4×10-7 s-1, and α=1.4×103 cm. Above this holmium concentration, energy transfer between Ho impurities also contributes to the losses. The spectral distributions of the Ho3+ emission cross section σEM for several laser channels are calculated in σ- and π-polarized configurations. The peak a σEM values achieved for transitions to the 5I8 level are ≈2×10-20 cm2 in the σ-polarized configuration, and three main lasing peaks at 2.02, 2.05, and 2.07 μm are envisaged inside the 5I7→5I8 channel 相似文献
2.
The authors report measurements of optically induced carrier-dependent refractive index changes and their saturation in an InGaAs single quantum well centered within a linear multiple quantum well guided-wave Fabry-Perot resonator using diode laser sources. A low-excitation nonlinear refractive cross-section, σn=-1×10-19 cm3, was deduced for probe wavelengths near the TM (transverse magnetic) absorption edge, falling only to σn=-3.1×10-20 cm3, at over 0.16 μm from the band edge. For an incident irradiance of 18 kW/cm 2, refractive index changes in the InGaAs quantum well as large as -0.16 were deduced near the absorption edge, while the index change at a wavelength 0.16 μm from the absorption edge was -0.055. This large off-resonant index change is attributed to an enhanced free-carrier contribution within a 2D system 相似文献
3.
Films of yttrium oxide (Y2O3) were deposited on Si substrates from a Y2O3 target by RF magnetron sputtering. MIS capacitors in the form of Al and Y2O3 (400 Å)-Si were then fabricated. The leakage current density was about 10-6 A/cm2 at 1.3×106 V/cm, and the breakdown field of the films was about 2.75×106 V/cm. The dielectric constant of the sputtered Y2O3 was found to be about 12-12.7 相似文献
4.
Bandgap-engineered W/Si1-xGex/Si junctions (p+ and n+) with ultra-low contact resistivity and low leakage have been fabricated and characterized. The junctions are formed via outdiffusion from a selectively deposited Si0.7Ge 0.3 layer which is implanted and annealed using RTA. The Si 1-xGex layer can then be selectively thinned using NH4OH/H2O2/H2O at 75°C with little change in characteristics or left as-deposited. Leakage currents were better than 1.6×10-9 A/cm2 (areal), 7.45×10-12 A/cm (peripheral) for p+/n and 3.5×10-10 A/cm2 (peripheral) for n+/p. W contacts were formed using selective LPCVD on Si1-xGex. A specific contact resistivity of better than 3.2×10-8 Ω cm2 for p +/n and 2.2×10-8 Ω cm2 for n+/p is demonstrated-an order of magnitude n+ better than current TiSi2 technology. W/Si1-xGe x/Si junctions show great potential for ULSI applications 相似文献
5.
具有高介电常数的栅绝缘层材料存在某种极化及耦合作用,使得ZnO-TFTs具有高的界面费米能级钉扎效应、大的电容耦合效应和低的载流子迁移率.为了解决这些问题,本文提出了一种使用SiO2修饰的Bi1.5Zn1.0Nb1.5O7作为栅绝缘层的ZnO-TFTs结构,分析了SiO2修饰对栅绝缘层和ZnO-TFTs性能的影响.结果表明,使用SiO2修饰后,栅绝缘层和ZnO-TFTs的性能得到显著提高,使得ZnO-TFTs在下一代显示领域中具有非常广泛的应用前景.栅绝缘层的漏电流密度从4.5×10-5A/cm2降低到7.7×10-7A/cm2,粗糙度从4.52nm降低到3.74nm,ZnO-TFTs的亚阈值摆幅从10V/dec降低到2.81V/dec,界面态密度从8×1013cm-2降低到9×1012cm-2,迁移率从0.001cm2/(V·s)升高到0.159cm2/(V·s). 相似文献
6.
N-channel metal oxide semiconductor field effect transistors (MOSFETs) using Ta2O5, gate oxide were fabricated. The Ta2O5 films were deposited by plasma enhanced chemical vapor deposition. The IDS-VDS and IDS-VGS characteristics mere measured. The electron mobility was 333 cm2/V·s. The subthreshold swing was 73 mV/dec. The interface trapped charge density, the surface recombination velocity, and the minority carrier lifetime in the field-induced depletion region measured from gated diodes were 9.5×1012 cm-2 eV-1, 780 cm/s and 3×10-6 sec, respectively. A comparison with conventional MOSFETs using SiO2 gate oxide was made 相似文献
7.
Beach R. Shinn M.D. Davis L. Solarz R.W. Krupke W.F. 《Quantum Electronics, IEEE Journal of》1990,26(8):1405-1412
A spectroscopic investigation of the biaxial crystal yttrium orthosilicate doped with Nd3+(Nd3+:Y2SiO5) has been performed. Spectrally and orientationally resolved emission cross sections necessary for the evaluation of laser performance on the Nd3+ 4F 3/2-4I 9/2 and 4F 3/2-4I 11/2 transitions have been determined. The Judd-Ofelt theory has been applied to measured values of optical absorption line strengths to obtain the orientation averaged intensity parameters: Ω2-3.34×10-20 cm2, Ω 4=4.35×10-20 cm2, and Ω6=5.60×10-20 cm2. These Judd-Ofelt intensity parameter values are significantly different from those previously reported by A.M. Tkachuk et al. Using these intensity parameters, the Nd3+ 4F 2 metastable state lifetime is predicted to be 225 μs. Measured low Nd concentration 4F 3/2 lifetimes of 214 μs indicate a high radiative quantum efficiency. Because of the Stark level splitting of the Nd3+ 4F 3/2 and 4I 9/2 manifolds, laser operation at twice one of the Cs atomic resonance filter acceptance wavelengths is possible 相似文献
8.
Yoshida A. Tamura H. Takauchi H. Hato T. Yokoyama N. 《Applied Superconductivity, IEEE Transactions on》1994,4(2):76-80
We measured the current-voltage characteristics of YBa2Cu3O7-x/oxide/n-SrTiO3 diodes using NdGaO3, LaAlO3, CeO2, and MgO as the oxide. MgO films had the highest current density. We then fabricated dielectric-base transistors with a YBa2Cu3 O7-x(YBCO) emitter/collector on a SrTiO3 dielectric base with an MgO barrier. The transistors had both voltage and current gains exceeding unity at 4.2 K. The emitter current density was about 4×103 A/cm2 at a collector-emitter voltage of 10 V and base-emitter voltage 10 V; this is 2 to 3 orders of magnitude larger than that of transistors with NdGaO3 emitter-base barrier. We obtained a transconductance of around 0.4 mS at a collector-emitter voltage of 10 V for a device with a 6-μm-diameter emitter 相似文献
9.
Lawrence B.L. Cha M. Kang J.U. Toruellas W. Stegeman G. Baker G. Meth J. Etemad S. 《Electronics letters》1994,30(5):447-448
Z-scan measurements at 1600 nm on single-crystal PTS (p-toluene sulfonate) with single, 65 ps pulses gave a complex nonlinear refractive index coefficient of n2=2.2(±0.3)×10-12 cm2/W at 1 GW/cm2 and α2<0.5 cm/GW. This is the first highly nonlinear, organic material to satisfy the conditions imposed by the figures of merit 相似文献
10.
Tunable Cr4+:YSO Q-switched Cr:LiCAF laser 总被引:1,自引:0,他引:1
Tunable passive Q-switching (781 nm to 806 nm at 300 K) of a flash-lamp pumped Cr3+:LiCaAlF6 (Cr:LiCAF) laser with a Cr4+:Y2SiO5 (Cr4+:YSO) broad-band solid-state saturable absorber has been realized. Typical pulse widths of the Q-switched laser output ranged from 40 ns to 80 ns, depending on the lasing wavelength. Spectral narrowing and reduced beam diameter with the use of the saturable absorber were observed. The ground state and the excited state absorption cross sections of the Cr4+:YSO absorber were found by bleaching experiments to be (7.0±1.4)×10-19 cm2 and (2.3±0.5)×10-19 cm2 at 694 nm, respectively. Numerical simulation was utilized to simulate the Cr:LiCAF passive Q-switching with Cr4+ :YSO solid-state saturable absorber 相似文献
11.
Burshtein Z. Blau P. Kalisky Y. Shimony Y. Kikta M.R. 《Quantum Electronics, IEEE Journal of》1998,34(2):292-299
An experimental study of saturable absorption and excited-state absorption (ESA) in several inorganic saturable absorbers, Cr4+ :YAG, Cr4+:GGG, and Cr4+:YSGG, is presented. We provide the theoretical background of absorption characteristics in saturable absorbers that exhibit ESA, with some new results: approximate analytical solutions are proposed for the optical transmission in the case of a slow absorber, and for various light intensity conditions of spatially or temporally Gaussian beams in fast and slow absorbers. Experimentally, partial bleaching of the first excited state itself could be observed in Cr4+:YAG at λ=1064 nm, yielding the higher excited-state lifetime as τ*=(0.55±0.1) ns. The regular transmission bleaching curve was measured in Cr4+:GGG, for the first time in this material, yielding σga=(58±5)×10-1 cm2, and σes=(13±2)×10-19 cm2 at λ=1064 nm, ESA spectra were measured for the three materials between ~700 and 900 nm. All three exhibit crossing between saturable absorption at longer wavelengths and inverse saturable absorption at shorter wavelengths 相似文献
12.
Hongyuan Shen Tianguan Lian Ruirong Zheng Yuping Zhou Guijang Yu Chenghui Huang Hong Liao Zhengdong Zheng 《Quantum Electronics, IEEE Journal of》1989,25(2):144-146
A method for the simultaneous measurement of the stimulated emission cross section and fluorescence lifetime by studying the relation between laser parameters and the laser relaxation oscillation frequency is discussed. The stimulated emission cross section for the 4F 3/2-4I 13/2 transition of Nd3+ ion in YAP crystal was measured to be (22±1)×10-20 cm2 相似文献
13.
Dyakonova N.V. Ivanov P.A. Kozlov V.A. Levinshtein M.E. Palmour J.W. Rumyantsev S.L. Singh R. 《Electron Devices, IEEE Transactions on》1999,46(11):2188-2194
Steady-state and transient forward current-voltage I-V characteristics have been measured in 5.5 kV p+-n-n+ 4H-SiC rectifier diodes up to a current density j≈5.5×10 4 A/cm2. The steady-state data are compared with calculations in the framework of a model, in which the emitter injection coefficient decreases with increasing current density. To compare correctly the experimental and theoretical results, the lifetime of minority carriers for high injection level, τph, has been estimated from transient characteristics. At low injection level, the hole diffusion length Lpl has been measured by photoresponse technique. For a low-doped n-base, the hole diffusion lengths are Lpl≈2 μm and Lph≈6-10 μm at low and high injection levels respectively. Hole lifetimes for low and high injection levels are τpl≈15 ns and τph≈140-400 ns. The calculated and experimental results agree well within the wide range of current densities 10 A/cm 23 A/cm2. At j>5 kA/cm2, the experimental values of residual voltage drop V is lower than the calculated ones. In the range of current densities 5×103 A/cm24 A/cm2, the minimal value of differential resistance Rd =dV/dj is 1.5×10-4 Ω cm2. At j>25 kA/cm2, Rd increases with increasing current density manifesting the contribution of other nonlinear mechanisms to the formation steady-state current-voltage characteristic. The possible role of Auger recombination is also discussed 相似文献
14.
The temperature dependence of the Cr-Nd energy transfer is found to be due to the thermal variation of the radiative decay probability of Cr. The validity of this conjecture is checked in the Gd3Sc 2Ga3O12 and CaMg2Y2 Ge3O12 crystals. It is also found that above 200 K, the nonradiative energy transfer rate from Cr to Nd is greater in Gd3Sc2Ga3O12 than in CaMg 2Y2Ge3O12 相似文献
15.
The change in refractive index Δn produced by injection of free carriers in InP, GaAs, and InGaAsP is theoretically estimated. Bandfilling (Burstein-Moss effect), bandgap shrinkage, and free-carrier absorption (plasma effect) are included. Carrier concentrations of 1016/cm3 to 1019/cm 3 and photon energies of 0.8 to 2.0 eV are considered. Predictions for Δn are in reasonably good agreement with the limited experimental data available. Refractive index changes as large as 10-2 are predicted for carrier concentrations of 10 8/cm3 suggested that low-loss optical phase modulators and switches using carrier injection are feasible in these materials 相似文献
16.
Dragornir A. McInerney J.G. Nikogosyan D.N. Ruth A.A. 《Quantum Electronics, IEEE Journal of》2002,38(1):31-36
The nonlinear absorption of water (H2O), heavy water (D 2O), ethanol, methanol, hexane, cyclohexane, 1, 2-dichloroethane, and chloroform at 264 nm was studied using femtosecond laser pulses. The two-photon absorption coefficients for these liquids were found to be between (34 ± 3) × 10-11 cm/W and (95 ± 11) × 10-11 cm/W 相似文献
17.
Shah P.B. Smith D.D. Griffin T.E. Jones K.A. Sheppard S.T. 《Electron Devices, IEEE Transactions on》2000,47(2):308-312
Shubnikov-de Haas (SdH) oscillation and Hall measurement results were compared with HEMT DC and RF characteristics for two different MOCVD grown AlGaN-GaN HEMT structures on semiinsulating 4H-SiC substrates. A HEMT with a 40-nm, highly doped AlGaN cap layer exhibited an electron mobility of 1500 cm2/V/s and a sheet concentration of 9×1012 cm at 300 K (7900 cm2/V/s and 8×1012 cm-2 at 80 K), but showed a high threshold voltage and high DC output conductance. A 27-nm AlGaN cap with a thinner, lightly doped donor layer yielded similar Hall values, but lower threshold voltage and output conductance and demonstrated a high CW power density of 6.9 W/mm at 10 GHz. The 2DEG of this improved structure had a sheet concentration of nSdH=7.8×1012 cm-2 and a high quantum scattering lifetime of τq=1.5×10-13 s at 4.2 K compared to nSdH=8.24×1012 cm-2 and τq=1.72×10-13 s for the thick AlGaN cap layer structure, Despite the excellent characteristics of the films, the SdH oscillations still indicate a slight parallel conduction and a weak localization of electrons. These results indicate that good channel quality and high sheet carrier density are not the only HEMT attributes required for good transistor performance 相似文献
18.
We demonstrate the performance of a Nd:YAG laser, passively Q-switched with a Cr4+:YAG plate, which plays the double role of a passive Q-switch and a Brewster plate. The Brewster plate configuration contributes an intracavity loss of approximately 3.2-10 -3 cm-1 along the cavity length. Losses contributed by the active Cr4+ ions in the plate relate to their excited state absorption. A freshly measured transmission saturation curve of Cr4+:YAG suggests a ground state absorption cross section σgs=(8.7±0.8)-10-19 cm2, and an excited state absorption cross section σes=(2.2±0.2)-10-19 cm2 of the Cr4+ ions at λ=1064 nm 相似文献
19.
Electrical characteristics of Al/yttrium oxide (~260 Å)/silicon dioxide (~40 Å)/Si and Al/yttrium oxide (~260 Å)/Si structures are described. The Al/Y2O3/SiO2/Si (MYOS) and Al/Y2 O3/Si (MYS) capacitors show very well-behaved I -V characteristics with leakage current density <10-10 A/cm2 at 5 V. High-frequency C - V and quasistatic C -V characteristics show very little hysteresis for bias ramp rate ranging from 10 to 100 mV/s. The average interface charge density (Q f+Q it) is ~6×1011/cm2 and interface state density D it is ~1011 cm-2-eV-1 near the middle of the bandgap of silicon. The accumulation capacitance of this dielectric does not show an appreciable frequency dependence for frequencies varying from 10 kHz to 10 MHz. These electrical characteristics and dielectric constant of ~17-20 for yttrium oxide on SiO2/Si make it a variable dielectric for DRAM storage capacitors and for decoupling capacitors for on-chip and off-chip applications 相似文献
20.
The single-pass (50 cm) amplifier performance of an atmospheric-pressure ArF laser pumped by a 65-ns full-width-at-half-maximum short-pulse electron beam was investigated theoretically for a wide range of excitation rates (0.1-2.0 MW/cm3 ). Atmospheric mixtures of Ne, Ar, and F2 (three mixtures of Ar=40%, 70%, and Ne-free) were studied. A kinetic numerical model of the ArF amplifier with a Ne buffer system was constructed. A one-dimensional propagation treatment considered the gain depletion and saturation absorption spatially and temporally along the optical axis. In this model the rate constants for electron quenching of ArF* of 1.6×10-7, 1.9×10-7, and 2.4×10 -7 cm3/s were used for Ar concentration of 40, 70 percent, and Ar/F2 mixture, respectively 相似文献