An Experimental Study of the Influence of an External Signal on the Generation Mode of a Megawatt-Power Gyrotron

The frequency capture of radiation by an external signal was experimentally studied for the first time for a megawatt-power gyrotron. An external signal from the magnetron at a frequency of 35 GHz entered the working space of the gyrotron through a synthesized two-mirror quasi-optical converter that allowed transforming the input signal into a working mode. This converter has been recently developed and implemented in the Institute of Applied Physics, Russian Academy of Sciences. The radiation spectra were experimentally obtained in modes of frequency capture and frequency beats. The dependence of the frequency capture bandwidth on the power of the external signal was found. Comparison of experimental results with the data of numerical modelling of gyrotron equations with an external signal showed their good agreement.     

Generation of chaotic microwave pulses in broadband self-oscillating ring system with ferromagnetic film under the action of external pulse-modulated microwave signal

We have experimentally studied specific features of the generation of chaotic microwave pulse trains in a self-oscillating ring system with nonlinear delay line on surface magnetostatic waves, bandpass filter, and power amplifier on GaAs field-effect transistors under the action of an external pulse-modulated microwave signal occurring outside the band of the generated chaotic signal. It is established that a decrease in the off/duty ratio in the external pulse-modulated microwave signal leads to an increase in this ratio for the chaotic microwave pulses. The integral power of the chaotic microwave signal generated under the pulsed external signal action is increased as compared to the power of signal generated in the autonomous regime.     

Stepwise current oscillations in tunnel and high-frequency semiconductor diodes

The response of tunnel and high-frequency diodes to an external harmonic signal of large amplitude has been studied. Stepwise current oscillations have been found on the current-voltage characteristics measured at a direct current when an external high-frequency signal is imposed simultaneously on the sample. The frequency of these oscillations decreases with increasing frequency of the external signal. Analogs of the appearance of stepwise current oscillations in semiconductor and other systems are indicated.     

Effect of external signal on the output power of an oscillator with electron feedback

The effect of an external single-frequency harmonic signal on the output power of an oscillator with electron feedback has been studied by analytical and numerical methods. It is established that an increase in the input signal power leads to sharp growth in the output power of the nonautonomous oscillator. Physical processes that take place in the electron beam with virtual cathode under the action of an external harmonic signal, which leads to velocity modulation in the electron beam entering the interaction space, have been analyzed. The obtained results well agree with the data of previous experimental investigations of the signal gain in a low-voltage vircator.     

Coherent resonance in klystron oscillator at self-excitation threshold

The phenomenon of coherent resonance in a nonlinear dynamical system based on a delayed-feedback klystron (DFK) oscillator has been experimentally studied. The application of an external white noise signal to the DFK oscillator at the self-excitation threshold leads to the appearance of a resonant response in the system, the maximum of which is attained at a definite power of the external noise. It is demonstrated for the first time that the coherent resonance in response to an external harmonic signal in the microwave range allows the signal-to-noise ratio at the output of a regenerative ring amplifier to be significantly increased.     

Frequency and phase stabilization of a multimode gyrotron with megawatt power by an external signal

We have numerically studied capturing of the oscillation frequency and phase of the TE28.12 operating mode by an external monochromatic signal for a multimode gyrotron with a close to real regime of activation. It is shown that, even at a low external-signal power, in a wide range of the magnetic field and voltage, a highly efficient single-mode generating is set at the frequency of the external signal.     

Characterizing the spatial-frequency sensitivity of perceptual templates

Filtered external noise has been an important tool in characterizing the spatial-frequency sensitivity of perceptual templates. Typically, low-pass- and/or high-pass-filtered external noise is added to the signal stimulus. Thresholds, the signal energy necessary to maintain given criterion performance levels, are measured as functions of the spatial-frequency passband of the external noise. An observer model is postulated to segregate the impact of the external noise and the internal noise. The spatial-frequency sensitivity of the perceptual template is determined by the relative impact exerted by external noise in each frequency band. The perceptual template model (PTM) is a general observer model that provides an excellent account of human performance in white external noise [Vision Res. 38, 1183 (1998); J. Opt. Soc. Am. A 16, 764 (1999)]. We further develop the PTM for filtered external noise and apply it to derive the spatial-frequency sensitivity of perceptual templates.     

Experimental study of the effect of external signal on microwave oscillations in a nonrelativistic electron beam with virtual cathode

The effect of an external harmonic signal on the characteristics of microwave generation in a non-relativistic electron beam with virtual cathode (VC) formed in a static retarding electric field (low-voltage vircator system) has been experimentally studied. A significant increase in the vircator generation power is observed when the frequency of the external signal is close to the frequency of VC oscillations. At large detunings, a broadband chaotic generation is observed.     

Resonant absorption of energy accompanying phase transitions in NaKC4H4O6·4H2O

Resonant absorption of external electric field energy was detected experimentally in the presence of phase transitions in Rochelle salt. An external alternating electric field leads to the appearance of an anomalous increase in the signal intensity at frequencies typical of those of the pulsed electric signal induced by a phase transition in the material. Pis’ma Zh. Tekh. Fiz. 24, 46–49 (August 26, 1998)     

Synchronization of spin-transfer nano-oscillator by an external source

The dynamics of a spin-transfer nano-oscillator (STN) of the point-contact type under the action of a spin wave excited in the ferromagnetic layer by an external source is considered. It is shown that the STN can be synchronized by this external source, and the regions of synchronism capturing and holding in the space of parameters are established. Dependences of the spin-wave amplitude on parameters of the external signal are presented.     

External signal suppresses automodulation in a gyro-backward-wave tube oscillator

Suppression of the automodulation of the output field in a gyro-backward-wave tube (gyro-BWT) by an external driving harmonic signal is demonstrated for the first time using the results of computer simulation. Parameters of the driving signal for which this phenomenon is possible have been determined.     

Delay line length selection in generating fast random numbers with a chaotic laser

The chaotic light signals generated by an external cavity semiconductor laser have been experimentally demonstrated to extract fast random numbers. However, the photon round-trip time in the external cavity can cause the occurrence of the periodicity in random sequences. To overcome it, the exclusive-or operation on corresponding random bits in samples of the chaotic signal and its time-delay signal from a chaotic laser is required. In this scheme, the proper selection of delay length is a key issue. By doing a large number of experiments and theoretically analyzing the interplay between the Runs test and the threshold value of the autocorrelation function, we find when the corresponding delay time of autocorrelation trace with the correlation coefficient of less than 0.007 is considered as the delay time between the chaotic signal and its time-delay signal, streams of random numbers can be generated with verified randomness.     

Experimental study of the effect of external noise-like signal on the dynamics of vircator with magnetron injection gun

The effect of an external noise-like signal on the operation of a low-voltage vircator with magnetron injection gun has been experimentally studied. The results show that the noise-like input signal allows the output characteristics of the low-voltage vircator to be controlled so as to drive it to operate at either maximum output power or maximum generation bandwidth.     

自由空间量子密钥分发中的信号同步解决方案

针对目前自由空间量子密钥分发（QKD）中的信号同步这一难点问题,提出一种采用外置光信号来解决信号同步问题的方案——光同步方案。在发送端利用声光调制器将外置激光器的连续激光分割成周期光脉冲序列,并作为同步光信号发送给接收端。接收端采用光电倍增管接收同步光脉冲信号,生成一个与发送端严格同步的信号,以此作为接收端的时基标准来进行单光子计数。采用高频的内部时钟信号来“监视”接收到的同步信号,从而提高计数准确性。该方案具有长距离性、无线性、低复杂度等特点,已成功应用于一个基于B92协议的自由空间QKD系统中。     

Features in dynamics of an almost conservative Ikeda map

Dynamics of the Ikeda map has been studied under conditions of very small dissipation, both in the autonomous regime and in the presence of an external noise signal. It is established that the system has a large number of coexisting low-period attractors (the lower the dissipation in the system, the greater the number of such attractors) and exhibits a rather long transient process. The action of an external noise leads to the breakage of most attractors.     

Tracking generator of calibrated harmonics

A tracking generator of calibrated harmonics has been tested at the Istituto Elettrotecnico Nazionale Galileo Ferraris. This system acquires the sinusoidal input supplied by a precision ac calibrator, and the internal DSP produces, by means of a digital-to-analog converter (DAC), an output signal combination of calibrated harmonics components, which is added to the sinusoidal signal of the calibrator. In this way, an ordinary 12-bit DAC can produce a precision signal with an assigned THD less than 10%. Some algorithms for generating the signal and for tracking with high accuracy the internal reference to the external input signal have been developed, which allow the frequency and phase difference to be recovered within 10/sup -4/ rad in less than 0.1 s.     

Beam-fanning novelty filter with enhanced dynamic phase resolution

We demonstrate a novel method to enhance the phase resolution of a barium titanate beam-fanning novelty filter by means of an external phase shift in one part of the signal wave. The new technique is described theoretically on the basis of the coupled-wave theory. Experimental results are presented to demonstrate the behavior and the advantages of the novel device for the evaluation of spatial and temporal phase changes in incident signal waves.     

Enhancement of the luminescence intensity of InAs/GaAs quantum dots induced by an external electric field

InAs/GaAs quantum dots have been subjected to a lateral external electric field in low-temperature microphotoluminescence measurements. It is demonstrated that the dot PL signal could be increased several times depending on the magnitude of the external field and the strength of the internal (built-in) electric field, which could be altered by an additional infrared illumination of the sample. The observed effects are explained by a model that accounts for the essentially faster lateral transport of the photoexcited carriers achieved in an electric field.     

The readout method for wire chambers

The method for readout of information from a wire chamber through a conventional conductive wire cathode is tested to study the possibility of its practical usage. It is observed that the value of the signal induced on an external readout electrode depends on the detector geometry and makes up approximately 5–10% of the anode signal value. The application of this method should permit one to separate a detector into an active device and an independent readout system as well as to make the readout system more flexible and to improve detector coordinate properties.     

Piezo-locking a diode laser with saturated absorption spectroscopy

We demonstrate modulation-based frequency locking of an external cavity diode laser, utilizing a piezo-electrically actuated mirror, external to the laser cavity, to create an error signal from saturated absorption spectroscopy. With this method, a laser stabilized to a rubidium hyperfine transition has a FWHM of 130 kHz over seconds, making the locked laser suitable for experiments in atomic physics, such as creating and manipulating Bose-Einstein condensates. This technique combines the advantages of low-amplitude modulation, simplicity, performance, and price, factors that are usually considered to be mutually exclusive.