共查询到20条相似文献,搜索用时 15 毫秒
1.
A theoretical model for the amplifiers predicts gain coefficients of around 2 dB per milliwatt of launched pump power, in close agreement with previously reported measurements. The model is also used to determine the optimal pump wavelength λopt that maximizes the amplifier gain. It is shown that the latter is insensitive to pump detuning near λopt=1.48 μm, within a 20 nm range, which indicates that broadband, multimode laser diode pump sources and pumps with narrow linewidths should yield identical gain performance 相似文献
2.
A report is presented of the thermal shifts of eleven of the twelve lines from the 4F 3/2 Stark energy levels to the 4I 11/2 energy levels in an Nd:YAG laser for a temperature change from 20-200°C. The thermal shift difference between the Stark sublevels R 1, R 2 in 4F 3/2 is found to be about -0.6±0.6 cm-1/100°C. Within experimental uncertainty, all of the lasing lines either moved to longer wavelength or remained unchanged with increasing temperature 相似文献
3.
Optimal pump wavelength in the4I 15/2-4I 13/2 absorption band for efficient Er3+-doped fiberamplifiers
Zyskind J.L. Giles C.R. Desurvire E. Simpson J.R. 《Photonics Technology Letters, IEEE》1989,1(12):428-430
The authors report the measured gain of a highly efficient erbium-doped fiber amplifier pumped at wavelengths between 1.46 and 1.51 μm. The optimal pump wavelength, λopt, was determined to be 1.475 μm. At this wavelength, the maximum gain coefficients for signals at 1.531 and 1.544 μm were 2.3 and 2.6 dB/mW, respectively. At λopt, high gains ranging from 32 dB at pump power P p=20 mW up to 40 dB at P p=80 mW were obtained. These modest pump powers are within the capabilities of currently available 1.48-μm diode lasers. The width about λopt for 3-dB gain variation exceeded 27 nm for P p=10 mW and 40 nm for P p >20 mW. With this weak dependence on pump wavelength, single-longitudinal-mode lasers do not have a significant advantage over practical Fabry-Perot multimode pump lasers 相似文献
4.
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
5.
Wolfmann J. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2001,47(5):1773-1779
We determine all linear cyclic codes over Z 4 of odd length whose Gray images are linear codes (or, equivalently, whose Nechaev-Gray (1989) image are linear cyclic codes or are linear cyclic codes) 相似文献
6.
Zyskind J.L. Desurvire E. Sulhoff J.W. Di Giovanni D.J. 《Photonics Technology Letters, IEEE》1990,2(12):869-871
Spectral gain hole-burning was observed at low temperatures in an erbium-doped fiber amplifier with GeO2:SiO2 core. At the peak wavelength λ=1.535 μm, homogeneous linewidths determined from the observed hole widths have a power-law dependence on temperature. At room temperature, the extrapolated homogeneous linewidth is 4 nm and the inhomogeneous linewidth is 8 nm 相似文献
7.
Aydin N. Ray-Chaudhuri D.K. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2002,48(7):2065-2069
Previously, (linear) codes over Z 4 and quasi-cyclic (QC) codes (over fields) have been shown to yield useful results in coding theory. Combining these two ideas we study Z 4-QC codes and obtain new binary codes using the usual Gray map. Among the new codes, the lift of the famous Golay code to Z 4 produces a new binary code, a (92, 224, 28)-code, which is the best among all binary codes (linear or nonlinear). Moreover, we characterize cyclic codes corresponding to free modules in terms of their generator polynomials 相似文献
8.
The fabrication and characterization of a 0.25-μm-gate, ion-implanted GaAs MESFET with a maximum current-gain cutoff frequency f t of 126 GHz is reported. Extrapolation of current gains from bias-dependent S -parameters at 70-100% of I dss yields f 1's of 108-126 GHz. It is projected that an f 1 of 320 GHz is achievable with 0.1-μm-gate GaAs MESFETs. This demonstration of f 1's over 100 GHz with practical 0.25-μm gate length substantially advances the high-frequency operation limits of short-gate GaAs MESFETs 相似文献
9.
Chunming Rong Helleseth T. Lahtonen J. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1999,45(5):1423-1434
The quaternary Calderbank-McGuire (see Des., Codes Cryptogr., vol.10, no.2, 1997) code is a Z 4-linear code of length 32 which has 237 codewords and a minimum Lee distance of 12. The Gray map of this code is known to be a nonlinear binary (64, 237,12) code. The Z 4-linear Calderbank-McGuire code can correct all errors with Lee weight ⩽5. An algebraic decoding algorithm for the code is presented in this paper. Furthermore, we discuss an alternative decoding method which takes advantage of the efficient BCH decoding algorithm 相似文献
10.
The OMDR (optical-microwave double resonance) spectrum of 87 Rb with the aim of using a frequency-stabilized GaAs semiconductor laser instead of an Rb lamp as a pumping source in a gas-cell-type Rb frequency standard. Natural isotope 87Rb was sealed in a glass cell with buffer gases (Ar/N 2=1.2, total pressure=39 torr). The double resonance signal in the 5P 1/2(F =2)←5S 1/2( F =1) transition appearing at the resonance to the F =2←1 hyperfine transition of the 5S 1/2 state was detected. The optimum operational cell temperature was 56°C. The peak-to-peak frequency width of the atomic hyperfine resonance discriminator used to stabilize the microwave frequency shifts induced by detuning of the laser frequency, changes in the laser and microwave powers, and temperature drift of the cell were investigated 相似文献
11.
A new projection method based on the row action projection (RAP) algorithm for image restoration is presented. The new implementation is computationally attractive and facilitates local adaption of projection operators. The local mean and the least L 1 norm set of solutions are used as constraints. Computer simulations illustrate the new methods to be very competitive in restoring missing spectral components of a degraded image 相似文献
12.
研究了室温下 NdP_5O_(14)晶体中 Nd~(3+)的4F_(3/2)态的荧光寿命。观察到高泵浦强度下影响光学增益的荧光双指数衰减曲线。从能量传递过程进行理论分析。简单描述了脉冲若丹明6G 激光器选择泵浦的τ计。 相似文献
13.
A simplified analytical expression for the temperature dependent saturated I D-V D characteristics of hydrogenated amorphous silicon (a-Si:H) thin-film transistors, between -50°C and 90°C, is presented and experimentally verified. The results show that the experimental transfer and output characteristics at several temperatures are easily modeled by a single equation. The model is based on three functions obtained from the experimental data of I D versus V G, over a range of temperature. Theoretical results confirm the simple form of the model in terms of the device geometry. As the temperature increased, the saturated drain current increased and, at a fixed gate voltage the device saturated at increasingly larger drain voltages while the threshold voltage decreased. Good agreement between the measured data and the model was obtained up to 363 K. Also observed at temperatures larger than 363 K was a decrease in I D and more severe gate voltage hysteresis characteristics 相似文献
14.
Rappaport T.S. Campbell R.L. Pocock E. 《Antennas and Propagation, IEEE Transactions on》1990,38(12):1967-1968
Standard textbook explanations of ionosphere propagation suggest that 30 MHz and 4000 km are the limiting frequency and distance for single-hop communications. During the peak of sunspot cycle 22, however, there have been hundreds of reports of F 2 communications exceeding great-circle distance of 4200 km at 50 MHz. It is shown that parabolic F 2 ionospheric models explain this propagation irregularity, although textbooks and reference books fail to show that such long distances at VHF are possible 相似文献
15.
Frequency stabilization of a 1.55 μm DFB laser diode is demonstrated using vibrational-rotational absorption of 12C 2H2 and 13C2H2 molecules (named VRAM). Frequency stability within 2 MHz peak to peak fluctuation can be achieved in the wavelength region of 1.51-1.55 μm. Frequency-stabilized DFB laser compact modules have been constructed. Frequency stabilities are evaluated by measuring the beat spectrum of the two lasers. In addition, the temperature and pressure dependences of the acetylene absorption lines are characterized 相似文献
16.
Nykolak G. Becker P.C. Shmulovich J. Wong Y.H. DiGiovanni D.J. Bruce A.J. 《Photonics Technology Letters, IEEE》1993,5(9):1014-1016
We report on the concentration- and pump-dependent lifetimes of the spontaneous emission in Er3+-doped fibers and Er3+ -doped waveguides. In addition, we measure the concentration dependence of the 550-nm fluorescence due to excited state absorption (ESA) 相似文献
17.
用441.56nm CW He-Cd+激光获得了39K2分子C1Ⅱu→X1∑g+跃迁的碰撞诱导(CI)光谱。光谱分析表明:来自C1Ⅱu(u′=0,J′=53)的碰撞诱导跃迁是P(△J=±2)、R(△J=±2)、Q(△J=±1)。碰撞诱导谱的波数计算值和实验值之间有令人满意的符合。研究了碰撞诱导(CI)伴线和激光诱导荧光(LIF)光谱主线的强度比ρ与缓冲气体压强、样品池温度的关系,给出了物理解释。 相似文献
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Direct measurements of the 4I11/2 terminal-laser-level lifetime of Nd:YLF after saturating a pumped sample with an impulse-like pulse are reported. Measurements of small-signal gain recovery at the 1047- and 1053-nm laser wavelengths in four different samples, as well as transient excited-state absorption from the terminal laser level, provide consistent values for this lifetime that average 21.6 ns with subnanosecond accuracy 相似文献