共查询到20条相似文献,搜索用时 31 毫秒
1.
2.
V. F. Shevchenko A. A. Petrov V. G. Petrov 《Journal of Infrared, Millimeter and Terahertz Waves》1993,14(9):1755-1768
A basic principle of pulse radar reflectometry is considered in this paper. A numerical analysis is performed in order to study errors appearing due to the expansion of a microwave pulse reflected from the plasma. A block diagram of the basic pulse radar scheme and its overall performance is presented. The first experimental results obtained on T11-M tokamak are discussed. An improved pulse radar scheme with cross-detection is considered. The results of bench test experiments and future applications of this scheme are discussed. 相似文献
3.
为了研究被动调Q激光器脉冲的波形对称特性,采用数值求解Nd:YAG晶体Cr4+:YAG被动调Q激光耦合速率方程组的方法,获得了激光脉冲的波形,绘制出了"脉冲对称因子"与饱和吸收体初始透过率和输出镜反射率的关系曲线图;并根据脉冲波形的不对称性,更精确地计算了脉冲宽度,及其与饱和吸收体初始透过率和输出镜反射率的关系.得到参数b=0.6时,脉冲波形对称;b=0.78时,脉宽最小的结论.结果表明,可以通过调整b参数来优化被动调Q脉冲波形对称性和脉宽. 相似文献
4.
5.
对国产掺镱(Yb3 )双包层大模场面积光纤超短脉冲放大器进行了系统的实验研究。以自己搭建的脉冲宽度为2.3ps,重复频率为95MHz的全固态锁模激光器作为种子源,以976nm大功率光纤耦合激光二极管为抽运源,以1.6m国产掺Yb3 双包层大模场面积光纤为增益介质,在11.2W的入纤抽运功率下,将平均功率为100mW的脉冲种子光放大到平均功率2.41W,单脉冲能量达到了25nJ,放大后脉冲的宽度(时域宽度)和光谱都有所展宽。 相似文献
6.
《Microwave Theory and Techniques》1967,15(2):96-100
Results are presented on the investigation of an experimental two-port magnetoelastic delay line using a single crystal rod of yttrium-iron-garnet, over the frequency range of 200 to 1000 MHz. A magnetic bias field is applied parallel to the rod axis. Data is given on delay time and insertion loss as a function of bias field. Both a slow and fast variation of insertion loss with bias field are noted. The slow variation of insertion loss is quite flat and insertion loss is at a minimum, over the range of 900 to 1050 oersteds, for all frequencies from 200 to 1000 MHz. A study of the fast variation of insertion loss shows that this variation occurs only over a portion of the pulse and if the pulse is short enough the fast variation is absent. A study of the effects of small permanent magnets that supply a biasing field orothogonal to the primary biasing field is presented. Insertion loss and pulse distortion are substantially reduced by these magnets. 相似文献
7.
为了研究激光-等离子体相互作用过程中的光子加速(光子频率上移),采用数值模拟方法进行了理论计算和数值计算验证,取得了光子加速的重要计算机模拟结果。结果表明,等离子体激光相互作用过程中的光子频率上移与所用的激光脉冲形式和脉冲宽度有关,存在最佳脉冲宽度和脉冲上升宽度,还存在等离子体电子密度上限。这一结果对进一步研究激光等离子体粒子加速有帮助。 相似文献
8.
A novel efficient circuit for Ultra-WideBand (UWB) balanced sub-nanosecond monocycle pulse generation is presented. The pulse generator employs wideband bipolar transistor, step recovery diodes, Schottky diodes, and simple charging and discharging circuitry. Simple transient analysis and design of the circuit are presented along with their operating principle. The pulse generator produces truly balanced monocycle pulse with 500 ps pulse-width and 800 mV peak voltage. The generated monocycle pulse also has very symmetrical positive and negative portions and low ringing level. The presented pulse generator can be used as both a transmitter feeding UWB balanced antennas without broadband baluns and a balanced switching pulse generator that used in UWB receiver. 相似文献
9.
10.
太赫兹脉冲整形技术研究进展 总被引:1,自引:0,他引:1
太赫兹(THz)脉冲整形技术在量子理论、生物医学成像、安全检查、亚毫米波通信等领域都具有重要的学术价值和应用前景。概述了基于飞秒脉冲的整形技术和新型太赫兹辐射材料整形技术,分析了太赫兹脉冲整形器件整形技术目前的研究状况,并对各种整形方法的发展进行了展望。 相似文献
11.
12.
A. E. Alekseev Ya. A. Tezadov V. T. Potapov 《Journal of Communications Technology and Electronics》2011,56(12):1490-1498
The results of the study of the statistical dependence of the backscattered light intensity of a semiconductor laser in a
single-mode fiber on the duration of the probing pulse and the source coherence time are presented. It is shown that, for
a given light coherence time, the intensity distribution function changes with increasing pulse duration from the function
close to the exponential one for the pulse duration approximately equal to the coherence time to the function close to the
Gaussian one for the pulse duration exceeding the coherence time. The exponential statistics of scattered light makes it possible
to obtain a higher sensitivity for the coherent reflectometer using the direct detection method. 相似文献
13.
An evaluation of a fiber optical parametric amplifier (FOPA)-based pulse source in terms of pulse width and chirp is presented. Experiments are performed when operating the FOPA as a pulse source, requiring a sinusoidally modulated pump. The FOPA is generating pulses at 10 GHz, and are measured using a streak camera capable of measuring pulses as a function of time, wavelength, and intensity. Experimental results are presented together with a theory for chirp and pulse widths that show good agreement. 相似文献
14.
An investigation of the propagation properties of a short pulse in a resonant absorber with a homogeneously broadened transition is presented with two main questions in mind: 1) the influence of the input pulse area on the transitory regime and on the steady-state propagation; 2) the effects of atomic coherence on the pulse shaping and the time delay of the leading edge of the pulse. The transitory regime of a propagating pulse is investigated and the stability of some asymptotic wave form confirmed. As expected, the transversal relaxation mechanism affects critically the major features of the coherent interaction. A detailed analysis of this problem is also presented. 相似文献
15.
16.
Modulation frequency and pulse duty cycle are two key parameters of pulsed VHF-PECVD technology. An experimental study on the mierocrystalline silicon materials prepared by pulsed VHF-PECVD technology in high deposition rate is presented. And combining the diagnosis of plasma process with optical emission spectroscopy (OES), the dependence of microstructure and electrical properties of thin films on the pulse modulation frequency is discussed in detail. 相似文献
17.
A theoretical analysis of the performance of a thermal defocusing optical limiter in the transient regime-i.e., when the laser pulse duration is comparable to the acoustic transit time which governs the limiter response-is presented. First, an expression is obtained for the time- and space-dependent refractive index changes induced by a laser pulse in an absorbing liquid. This is used to calculate the nonlinear phase change experienced by the laser pulse while traversing the absorbing medium and then the transmission of the optical limiter. Results on the dependence of the optical limiter's performance on laser pulse duration are presented in a general form and also by considering a specific example 相似文献
18.
本文对超短光脉冲在半导体激光放大器内的放大过程进行理论和实验研究,首次推导出描述这一瞬态变化过程的一系列方程组,并利用方程组进行了数值模拟求解,最后给出与理论相一致的实验结果。 相似文献
19.
Golestani K. Chandrasekar T. Keeler R.J. 《Geoscience and Remote Sensing, IEEE Transactions on》1995,33(2):239-246
Weather radars require long unambiguous ranges, high Nyquist sampling rates and good clutter suppression. In addition, polarization diversity is also used extensively, switching polarization of the transmit pulse on a pulse by pulse basis. This paper presents a dual polarized staggered pulse repetition scheme that can be used for Doppler and polarization diversity measurements in a weather radar. Processing algorithms for radar returns under this scheme are also presented. This pulsing scheme was implemented on the CP-2 radar operated by the National Center for Atmospheric Research. Experimental observations of convective storms using dual polarized staggered pulse repetition scheme in the Colorado front range were made and the results of the data analysis are presented 相似文献
20.
Vazquez J.M.M. Nilsson H.H. Zhang J.-Z. Galbraith I. 《Quantum Electronics, IEEE Journal of》2006,42(10):986-993
The linewidth enhancement (alpha-) factor of quantum-dot (QD) semiconductor optical amplifiers in the small signal gain and nonlinear regimes is theoretically investigated. A microscopic polarization equation and a wave equation are used to model subpicosecond pulse propagation in the nonlinear regime. In addition, a population equation that takes into account spectral hole burning and carrier heating effects is used. A novel approach to obtain the alpha-factor from the output pulse amplitude and phase in the dynamic nonlinear regime is presented. An in-depth study reveals that the presence of excited states (ES) limits the alpha-factor to values greater than 1 except when the energy separation between the ground state and ES is large. The alpha-factor dependence on QD inhomogeneous broadening, carrier density, carrier temperature, energy level separation, and input pulse energy is analyzed. We find that these can change the alpha-factor considerably. In particular, the alpha-factor increases with increasing input pulse energy and can be greater than 10 for input pulse energies larger than the amplifier's input pulse saturation energy. In the light of our calculations, the optimum device engineering required to obtain a low alpha-factor is discussed 相似文献