Coherent approach to analysis of modulated optical radiation

A method is proposed for determining the modulation parameters of optical radiation that does not require wide-band photodetectors for modulation at high and microwave frequencies. The method is based on measurement of the time coherence of optical radiation containing a modulation signal.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 25–28, April, 1930.     

Entrainment and stimulated emission of ultrasonic piezoelectric auto-oscillators

Theoretical modeling and laboratory tests are conducted for nonlinear auto-oscillating piezoelectric ultrasonic devices coupled to reverberant elastic bodies. The devices are shown to exhibit behavior familiar from the theory of coupled auto-oscillators. In particular, these spontaneously emitting devices adjust their limit-cycle frequency to the spectrum of the body. It is further shown that the auto-oscillations can be entrained by an applied field; an incident wave at a frequency close to the frequency of the natural limit cycle entrains the oscillator. Special attention is paid to the phase of entrainment. Depending on details, the phase is such that the oscillator can be in a state of stimulated emission: the incident field amplifies the ultrasonic power emitted by the oscillator. These behaviors are essential to eventual design of an ultrasonic system that would consist of a number of such devices all synchronized to their mutual field, a system that would be an analog to a laser. A prototype uaser is constructed.     

Acoustic radiation from a drop due to its nonlinear vibrations

It is shown that the intensity of acoustic radiation from a vibrating drop depends mainly on the monopole and dipole components appearing only in the second order of smallness in vibration amplitude. The intensity of the quadrupole acoustic radiation generated by the vibration fundamental mode in the first order of smallness in amplitude turns out to be much weaker. This is associated with the fact that, if the acoustic wavelength is much larger than the drop characteristic size, their ratio becomes a governing small parameter, being lesser than the ratio of the drop vibration amplitude to the drop linear size. Analytical estimates of the amplitudes of monopole, dipole, and quadrupole components of the velocity field associated with the acoustic field of the drop.     

Electromagnetic radiation due to nonlinear oscillations of a charged drop

The nonlinear oscillations of a spherical charged drop are asymptotically analyzed under the conditions of a multimode initial deformation of its equilibrium shape. It is found that if the spectrum of initially excited modes contains two adjacent modes, the translation mode of oscillations is excited among others. In this case, the center of the drop’s charge oscillates about the equilibrium position, generating a dipole electromagnetic radiation. It is shown that the intensity of this radiation is many orders of magnitude higher than the intensity of the drop’s radiation, which arises in calculations of the first order of smallness and is related to the drop’s charged surface oscillations.     

Thermally stimulated effects in dielectrics and their application to radiation dosimetry

Certain dielectric materials show transient phenomena on heating following X- or γ- irradiation. There are three related phenomena which display the same pattern of behaviour, (a) thermoluminescence (T.L.); (b) thermally stimulated conductivity (T.S.C.); (c) exoelectron emission (T.S.E.).

The physics of these thermally stimulated effects is discussed and the development of dosemeters utilising them is described. So far only T.L. is used in a commercially available dose measuring system. Dosimetry using T.S.C. and T.S.E. is still at the research stage.     

Liquid optical fibers with a multistable core actuated by light radiation pressure

We report on spatiotemporal behavior of self-adapted dielectric liquid columns generated and sustained by light radiation pressure. We show that single- or multivalued liquid column diameter depends on the excitation light beam. When the beam diameter is sufficiently small, we observe a well-defined stationary column diameter. In contrast, at a larger beam diameter, the liquid column experiences complex spatiotemporal dynamics whose statistical analysis evidences an underlying multistable structure. Experimental observations are all supported by a full electromagnetic model that accounts for the wave guiding properties of the liquid column viewed as a step-index liquid-core liquid-cladding optical fiber having an optically tunable core diameter.     

Application of refraction and diffraction of light to the measurement of the liquid surface shape deformed by ultrasonic radiation pressure

A method of measuring the liquid surface (hump) deformed by ultrasonic radiation pressure is proposed. The method is based on the usage of a hump as a liquid lens with an interference structure formed by sound waves falling on the surface. The hump shape is evaluated by means of shadowgrams obtained with laser illumination. The possibility of using the hump as a sensor of processes occuring in the liquid through which sound waves are passing is shown.     

An optically stimulated luminescence study of porcelain related to radiation dosimetry

This article describes the essential features regarding the photo-stimulated luminescence of porcelain: both the main ceramic and glazing materials are studied. In each case, radiation dose dependent signals are observed, superimposed on dose independent luminescence transitions that are both Stokes and anti-Stokes shifted in energy. Glazing is shown in some cases to be considerably more sensitive as a radiation dosemeter than the main porcelain ceramic. By comparison with the properties of artificial phosphors, the principal luminescent matrix is identified as being Al₂O₃, and the recombination centres in one glazing type are shown to be F-centres, Cr³⁺ and Dy³⁺.     

An optically stimulated luminescence study of flint related to radiation dosimetry

This article describes the essential features of photo-stimulated luminescence in flint. The emission is shown to be complex, arising from a number of different aspectsof the material. Under constant illumination, dose-dependent time-decaying anti-Stokes signals are superimposed on dose-independent, time-stable emission that is both Stokes and anti-Stokes shifted in energy. It is argued that the dose-dependent signals arise from the crystalline quartz phase of the material, whereas the dose independent signals originate from an amorphous-like phase of SiO₂. The microcrystallinity of the material leads to contrasting behaviour when compared with bulk crystalline quartz.     

Macroscopic thermal entanglement due to radiation pressure

Can entanglement and the quantum behavior in physical systems survive at arbitrary high temperatures? In this Letter we show that this is the case for a electromagnetic field mode in an optical cavity with a movable mirror in a thermal state. We also identify two different dynamical regimes of generation of entanglement separated by a critical coupling strength.     

On the interaction of stimulated spin-flip raman scattering and stimulated recombination radiation in InSb

We have studied the interaction of stimulated spin-flip Raman scattering and stimulated recombination radiation in n-InSb using a CW CO pump laser. A change in linewidth and output power of second Stokes spin-flip radiation is observed when the tuning curve of the first Stokes stimulated spin-flip radiation and the stimulated recombination radiation cross. The observations are explained using a simple rate equation model.     

High-energy behavior of jet and lepton-pair production

The cross section for jet and lepton-pair production at large transverse momenta has been studied to all orders in QCD perturbation theory. Appropriate moments of these cross sections are seen to factorize short-distance from long-distance dependence, and scale breaking is governed by the anomalous dimensions of twist-two operators.     

Simulation of seismic response to the action of a rain drop

The seismic response to the action of a falling rain drop on the ground is simulated in laboratory. The pulse signal from the output of accelerometers set up near points near the falling of a drop on a hard surface was experimentally recorded. The level is measured, and the spectrum of the vibration signal is analyzed. The theoretical estimates of the level and spectrum of the elastic-wave response agree with the results of experiment. The simulation results can be used to reduce the level of noise caused by precipitation, as well as to study the features of a moving droplet interacting with a hard boundary.

     

The connection between sound production and jet structure of the supersonic impinging jet

An experimental investigation into the sound-producing characteristics of moderately and highly underexpanded supersonic impinging jets exhausting from a round convergent nozzle is presented. The production of large plate tones by impingement on a square plate with a side dimension equal to 12 nozzle exit diameters is studied using random and phase-locked shadowgraph photography. Discrete frequency sound is produced in the near-wall region of the jet when a Mach disk occurs upstream of the standoff shock wave. Tones cease when the plate distance is approximately 2.2 free-jet cell lengths and the first and second shock waves are located in the free-jet positions. The production of impulsive sound appears to be associated with the collapse of the standoff shock wave during a portion of the oscillation cycle. Results from unsteady plate-pressure measurements indicate that plane-wave motion occurs in the impingement region and a secondary pressure maximum is observed on the plate adjacent to the flow region where sound appears to originate.     

Response of tunnel schottky-barrier junctions to radiation pressure of fir laser radiation

The response of tunnel Schottky junctions due to plasma reflection of laser radiation has been investigated in the far infrared. The signal was found to be independent of the laser radiation frequency below the plasma edge. At high power levels a nonlinearity of the response was observed. It is assumed that this nonlinearity is caused by near-zone field effects which lead also to a substantial enhancement of the responsivity.On leave from A. F. Ioffe Physico-Technical Institute of the Russian Academy of Sciences St. Petersburg 194021, Russia     

Generalized response of a sphere embedded in a viscoelastic medium excited by an ultrasonic radiation force

The response of an embedded sphere in a viscoelastic medium excited by acoustic radiation force has been studied in both the time- and frequency-domains. This model is important because it can be used to characterize the viscoelastic properties of the medium by fitting the response to the theoretical model. The Kelvin-Voigt model has been used exclusively in these models. An extension to the previously reported models is described so that any viscoelastic rheological model can be used. This theoretical development describes the generalized embedded sphere response both in the time and frequency domains. Comparing the results from derivations in both domains showed very good agreement with a median absolute error (MAE) ranging from 0.0044 to 0.0072. Good agreement is demonstrated with finite element model simulations and the theory with a MAE of 0.006. Lastly, results for characterization of gelatin and rubber materials with the new theory are shown where the MAE values were used to determine which rheological model best describes the measured responses.