Stretching,Amplification, and Compression of Microwave Pulses Using Helically Corrugated Waveguides

Radiophysics and Quantum Electronics - We demonstrate the possible implementation of the chirped pulse amplification (CPA) method, which is widely used in optics, for the microwave frequency band....     

偏振调制的光纤温度传感器补偿结构的进一步分析

The equivalent temporal complex parameter for Sech type pulses is introducted. The pulse transformation property and optimum compression condition are derived when the pulse passes through grating pair.     

Generation of Powerful Ultrashort Microwave Pulses

We study theoretically and experimentally the possibility of generation of ultrashort powerful microwave pulses. The regime of spatial accumulation of electromagnetic energy is considered in the case where the pulse propagates oppositely to the electron flow in a long slow-wave structure. We show that during transformation of the kinetic energy of electrons to the energy of an electromagnetic pulse, the pulse power is not limited by the electron-beam power. Using compact high-current accelerators, we obtain gigawatt pulses in the 3-cm and 8-mm wavelength ranges with power conversion factor exceeding unity.     

Compression of Nanosecond Pulses upon Reflection from a Thermally Nonlinear Medium

We consider a boundary-value problem for nonlinear total internal reflection of laser pulses from a semi-infinite thermally nonlinear medium. Numerical modeling of the pulse forming upon reflection under the conditions of interaction of counter-propagating waves in a scheme with a retrodirective mirror has been carried out the approximation of noninterfering pulses, the possibility of controlling the shape and compression of the pulse in the nanosecond range of durations has been shown. The results obtained are in qualitative agreement with the known experimental data.     

梳状色散光纤中皮秒脉冲压缩特性研究

利用数值法解非线性薛定谔方程,分析了光脉冲在梳状色散光纤中的传输特性,比较了光脉冲在几种不同的色散变化趋势的梳状色散光纤中的脉冲压缩比及脉冲质量,提出了高阶孤子压缩加梳状色散光纤压缩的方法,并初步讨论了梳状色散光纤对增益开关激光器输出脉冲进行压缩的效果。     

Magnetization of Paramagnetic Ions by Phase-Modulated Microwave Pulses in a Zero Magnetic Field

Physics of the Solid State - The effect of magnetization formation for paramagnetic ions with spin S = 1 in a solid under a zero magnetic field by pulsed manipulations with electron spins has been...     

Thermoacoustic Method for Detection of Powerful Microwave Pulses

We propose a method for detection of the envelope of a microwave nanosecond pulse, which is based on the effect of generation of sound pulses resulting from absorption of electromagnetic waves. We show that to reproduce exactly the envelope shape of a short microwave pulse, it is necessary that the wave be absorbed in a layer of thickness much less than the product of the sound speed and the pulse duration. In searching for conditions ensuring this, we study the process of thermoacoustic generation in thin metal films deposited on quartz substrates. Measurements performed at a wavelength of 8 mm show that the absorption coefficient is maximum if the aluminum-film thickness is 22–25 Å. The maximum absorption coefficient amounts to 49% if the wave is incident from the quartz-substrate side. It is important that in this case, the wave reflection coefficient does not exceed 44%, whereas an aluminum plate reflects almost completely (99.8%) the incident-wave power. The phenomena observed in thin metal films are explained theoretically in terms of the anomalous skin effect. An experimental setup for a study of generation of ultrasonic signals by powerful microwave pulses is described.     

基于光纤光参量放大的光脉冲压窄技术的研究

在高重复频率的光窄脉冲源中,为了获得更窄的脉冲,需要增加泵浦功率|但泵浦功率的提高会使光放大器的增益趋于饱和,放大的自发辐射噪音增强,脉冲光信噪比下降.为此,提出了利用啁啾管理和光纤光参量放大相结合的脉冲压窄方案.将强度调制后的泵浦光通过相位调制引入线性负啁啾,由于经参量过程后在新的闲频光上啁啾会加倍,从而进一步增大了信号的谱宽,并通过色散补偿介质实现了光脉冲压缩.实验给出了10 GHz速率下的结果,通过泵浦光的相位调制在0.5 W平均泵浦光功率条件下得到了脉宽19 ps的光脉冲,结果与理论分析基本吻合.     

基于光纤光参量放大的光脉冲压窄技术的研究

在高重复频率的光窄脉冲源中,为了获得更窄的脉冲,需要增加泵浦功率;但泵浦功率的提高会使光放大器的增益趋于饱和,放大的自发辐射噪音增强,脉冲光信噪比下降.为此,提出了利用啁啾管理和光纤光参量放大相结合的脉冲压窄方案.将强度调制后的泵浦光通过相位调制引入线性负啁啾,由于经参量过程后在新的闲频光上啁啾会加倍,从而进一步增大了...     

色散缓变光纤中超短光脉冲的绝热压缩

报道了色散缓变光纤中超短光脉冲压缩效应的实验结果。采用两段长度分别为100m和500m的色散缓变光纤，成功地将分布反馈激光器输出的4.4ps光脉冲压缩到1.1ps和830fs，脉冲压缩比分别为4.0和5.3。研究还发现，色散沿纵向变化较慢的光纤有利于脉冲的进一步压缩，理论分析与实验结果一致。     

Active Bragg Compressor of 3-cm Wavelength Microwave Pulses

We present the results of studies of the active compressor of 3-cm wavelength microwave pulses, which uses a high-Q storage Bragg resonator excited at the H₀₁ mode and new types of plasma switches. Phase variation during a compressed pulse and phase correlation of the input and compressed microwave pulses are studied both experimentally and theoretically. Using a single-channel compressor excited at the megawatt power level by the magnicon radiation with frequency 11.4 GHz, a power amplification factor equal to 9 was reached for an output-pulse duration of 40–50 ns and a peak power of up to 25 MW. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 7, pp. 597–616, July 2008.     

皮秒脉冲在色散缓变光纤中的孤子效应压缩

本文给出了描述皮秒脉冲在色散缓变单模光纤中孤子效应压缩过程的数学模型。通过数值求解，首次对该孤子效应压缩进行了全面的计算和分析。结果表明，与常规光纤相比，采用色散缓变程度合适的光纤压缩皮秒脉冲，不仅能显著地提高压缩后脉冲的峰值功率和脉冲压缩比，而且能有效地消除压缩后脉冲的次峰和脉座。对于确定的脉冲输入，发现，当光纤的色散缓变程度取某一最佳值时，能获得最佳的压缩效果。进一步研究表明，色散的这一最佳变     

1.3μmDFB半导体激光超短脉冲的产生及其压缩

本文首次报道１．３μｍ单模超短脉冲产生及压缩实验。通过梳状波电脉冲直接调制ＤＣＰＢＨ－ＤＦＢ半导体激光器，获得２２ｐｓ单模光滑脉冲；然后利用Ｇ－Ｔ干涉仪压缩得到近变换极限超短脉冲。脉宽为９．３ｐｓ，峰值功率超过２００ｍＷ，重复频率１ＧＨｚ，时间带宽乘积为０．３９，脉冲压缩比为２．４。最后对实验结果进行了讨论。     

Coherent Control of Population Transfer in Li Atoms via Chirped Microwave Pulses

We demonstrate theoretically that Li atoms can be transferred to states of a lower principal quantum number by exposing them to a frequency chirped microwave pulse. The population transfer of Li atoms from the n = 75 state to n = 70 with more than 90% efficiency is achieved by means of the sequential single-photon △n = -1 transitions. The calculation fully utilizes all of the available orbital angular momentum l states for a given n, and the interference pattern and population evolution dynamics of individual l states are analyzed in detail. Using the time-dependent multilevel approach, we describe the process reasonably well as a sequence of adiabatic rapid passages.     

Microwave Spin Frequency Comb Memory Protocol Controlled by Gradient Magnetic Pulses

We have demonstrated a combination of frequency comb spin-echo protocol in a conventional microwave pulsed electron spin resonance spectrometer with gradient pulses of the external magnetic field applied for on-demand retrieval of signal microwave pulses at the required moments of time. A natural high-finesse periodic structure was used as a carrier of stored information. The structure is made out of hyperfine lines of electron spin resonance of tetracyanoethylene anion radicals in toluene at room temperature. Herein, we have also observed that using the pulses of gradient magnetic field can increase the memory capacity. The experimental results demonstrated promising opportunities for controlling electron nuclear spin coherence, which could be useful for implementation of broadband microwave or optical-microwave noise free quantum memory protocols.     

Wide-Aperture Liquid Calorimeters for Measuring the Energy of Powerful Microwave Radiation Pulses

Russian Physics Journal - An overview was done of the efficient devices designed to measure the energy of powerful electromagnetic radiation pulses of the relativistic microwave sources –...     

Generation of Microwave Pulses with a Carrier Frequency of 3.8 GHz and a Length of 75 ns by a Relativistic Cherenkov Microwave Oscillator without a Guiding Magnetic Field

In the experiment with an electron energy of ≈500 keV, the long-pulse (~300T, where T is the oscillation period) the generation regime of a relativistic Cherenkov microwave oscillator without a guiding magnetic field at a carrier frequency of 3.8 GHz has been obtained. A high-power microwave radiation pulse length of ~75 ns, a peak generation power of 210 ± 30 MW, and a power conversion efficiency of 9 ± 2% were attained.     

光学耦合腔中类电磁感应透明现象的实验研究

光学耦合腔可以模拟原子系统中的电磁感应透明(Electromagnetically induced transparency,EIT)效应.采用分离光学腔镜建立耦合腔,该系统易于调节腔的各种参数.通过改变中间耦合腔镜的不同透射率,实验测量了两耦合腔的反射谱,观测到两耦合腔由于经典相消干涉产生的类EIT现象.由于该系统简单灵活,可用于慢光速和超光速的实验研究.