Probe Light Beam Research Articles

Generating grating in cavity magnomechanics

Abstract We investigate the phenomenon of magnomechanically induced grating (MMIG) within a cavity magnomechanical system, comprising magnons (spins in a ferromagnet, such as yttrium iron garnet), cavity microwave photons, and phonons (Li et al 2018 Phys. Rev. Lett. 121 203601). By applying an external standing wave control, we observe modifications in the transmission profile of a probe light beam, signifying the presence of MMIG. Through numerical analysis, we explore the diffraction intensities of the probe field, examining the impact of interactions between cavity magnons, magnon-phonon interactions, standing wave field strength, and interaction length. MMIG systems leverage the unique properties of magnons, and collective spin excitations with attributes like long coherence times and spin-wave propagation. These distinctive features can be harnessed in MMIG systems for innovative applications in information storage, retrieval, and quantum memories, offering various orders of diffraction grating.

Temporal cloaking via the effect of Compton scattering

In this work we have studied Temporal Cloaking in a 4 level atomic system in the presence of Compton scattering effect. Between the scattered and un-scattered probe light beams multiple time gaps are noted. Furthermore, it is noted that Compton scattering angle has significant influence on the time gap produced in the system. The time gap increased rapidly by increasing the value of φ up to π/2 and then changes slowly. Temporal time gap up to the order of microseconds is noted which might be useful in information hacking technology. Moreover, the time gap is further modified with pulse width, that could have significant applications in secured communication cloaking devices.

Nonlocal phase modulation of multimode, continuous-variable twin beams

We investigate experimentally the nonlocal phase modulation of multiple-frequency-mode, continuous-variable entangled twin beams. We use a pair of electro-optical phase modulators to modulate the entangled probe and conjugate light beams produced by four-wave mixing in hot rubidium vapor. A single phase modulator in either one of the twin beams reduces the two-mode squeezing signal. The overall quantum entanglement is preserved, however, as the modulator nonlocally distributes the beam correlations among frequency modes of the multimode fields. The two-mode squeezing can be recovered by reversing the mixing with an additional out-of-phase electro-optical phase modulator (EOM) in the other beam.

Gain Assisted Raman Induced Classical and Quantum Talbot Imaging

Abstract2D Raman generated classical and quantum Talbot imaging is proposed in a three‐level gain assisted system. First, a 2D Raman induced grating (RIG) will be constructed by modulating transmission function in the weak probe channel using a strong control standing wave field. Furthermore, RIG will diffract a probe field, by shining a probing light beam on an optically generated lattice within a rubidium vapor cell. This study uses gain assisted Raman medium [Nature 406, 277 (2000)] to examine classical and quantum Talbot imaging. In the case of Raman‐induced classical imaging, the diffraction pattern repeats itself at planes with integer multiple Talbot lengths. Additionally, by taking into account entangled photon pairs, the scenario of Raman‐induced quantum imaging is investigated. This study also looks at the RIG's amplitude and phase information with adjustable image size variation. As a result of the gain feature and zero absorption, this system is anticipated to be more suitable from the perspective of application. This analysis may pave the way for further research into the Talbot effect's nonlinear and quantum dynamical properties. Also, it provide a non‐destructive, lensless method for imaging very cold atoms or molecules.

Time-domain Brillouin scattering theory for probe light and acoustic beams propagating at an angle and acousto-optic interaction at material interfaces

A theory has been developed to interpret time-domain Brillouin scattering (TDBS) experiments involving coherent acoustic pulse (CAP) and light pulse beams propagating at an angle to each other. It predicts the influence of the directivity pattern of their acousto-optic interaction on TDBS signals when heterodyne detection of acoustically scattered light is in backward direction to incident light. The theory reveals relationships between the carrier frequency, amplitude and duration of acoustically induced ”wave packets” in light transient reflectivity signals, and factors such as CAP duration, widths of light and sound beams, and their interaction angle. It describes the transient dynamics of these wave packets when the light and CAP encounter material interfaces, and how the light scattering by the incident CAP transforms into scattering by the reflected and transmitted CAPs. The theory suggests that single-point TDBS experiments can determine not only depth positions of buried interfaces but also their local inclinations/orientations.

Design considerations for an ultrahigh-bandwidth Phase Contrast Imaging system applied to fusion grade devices

The PCI diagnostic is an internal reference interferometer that creates an image of absolutely calibrated electron density fluctuations integrated along the line of sight of the probing light beam. While conventional PCI diagnostics installed on fusion experiments worldwide employ light of wavelength equal to 10.59 μm, the same system using light at 1.55 μm wavelength would extend the spectral response in wave-number and frequency by factors of seven and over one hundred, respectively, thereby potentially providing quantitative measurements of the internal structure of density perturbations induced by either turbulent or radio-frequency waves, simultaneously covering ion to electron gyro-radius scales up to the GHz frequency region. Based on a previously developed 1.55 μm PCI prototype system, constraints to the design for such a diagnostic in fusion grade devices are presented and compared to those faced with the conventional method.

Оптическая гильберт-томография газовых струй

Hilbert-optics and signal conversion methods form the basis for modern information and measurement technologies. The Hilbert transform in the frequency space is physically reduced to a certain phase transformation of the Fourier spectrum of the signal in a wide frequency band. The article discusses the possibility of Hilbert tomography using the example of studying the isothermal flow of a freon-22 jet. An optical system based on the IAB-463M modernized wide-aperture shadow device has been developed. This system makes it possible to perform four-angle diagnostics of the studied phase object using probing light beams. The beams orientation is defined at angles of 0, π/2, π/4 and 3π/4 to the optical axis of the shadow device. This makes it possible to simultaneously register all four tomographic projections in the form of Hilbert images in separate sections of the CCD-matrix of the high-speed camera. The use of the iterative Gershberg-Papulis scheme for finding the parameters of the medium under study based on Hilbert tomography data is further proposed. This algorithm for reconstructing a function from its Radon data obtained by a limited number of projections consists in iterative transitions from estimating the function in the Fourier plane to its estimate in the spatial domain, corrected based on a priori information. The spectrum of the restored function is determined on the entire frequency plane as a result of an iterative process, which makes it possible to determine the values of the required function.

Cooling of the Nuclear Spin System of a Nanostructure by Oscillating Magnetic Fields.

We propose a method of cooling nuclear spin systems of solid-state nanostructures by applying a time-dependent magnetic field synchronized with spin fluctuations. Optical spin noise spectroscopy is considered a method of fluctuation control. Depending on the mutual orientation of the oscillating magnetic field and the probe light beam, cooling might be either provided by dynamic spin polarization in an external static field or result from population transfer between spin levels without build-up of a net magnetic moment ("true cooling").

Phase-insensitive amplifier gain estimation at Cramér-Rao bound for two-mode squeezed state of light.

Phase-insensitive amplifiers (PIAs), as a class of important quantum devices, have found significant applications in the subtle manipulation of multiple quantum correlation and multipartite quantum entanglement. Gain is a very important parameter for quantifying the performance of a PIA. Its absolute value can be defined as the ratio of the output light beam power to the input light beam power, while its estimation precision has not been extensively investigated yet. Therefore, in this work, we theoretically study the estimation precision from the vacuum two-mode squeezed state (TMSS), the estimation precision of the coherent state, and the bright TMSS scenario, which has the following two advantages: it has more probe photons than the vacuum TMSS and higher estimation precision than the coherent state. The advantage in terms of estimation precision of the bright TMSS compared with the coherent state is researched. We first simulate the effect of noise from another PIA with gain M on the estimation precision of the bright TMSS, and we find that a scheme in which the PIA is placed in the auxiliary light beam path is more robust than two other schemes. Then, a fictitious beam splitter with transmission T is used to simulate the noise effects of propagation loss and imperfect detection, and the results show that a scheme in which the fictitious beam splitter is placed before the original PIA in the probe light beam path is the most robust. Finally, optimal intensity difference measurement is confirmed to be an accessible experimental technique to saturate estimation precision of the bright TMSS. Therefore, our present study opens a new avenue for quantum metrology based on PIAs.

Spin-noise spectroscopy of a spin-one system

The spin-noise mechanisms in a spin-1 system are theoretically and experimentally investigated in detail. Eight different independent spin degrees of freedom are isolated, leading to spin-noise signals at the Larmor frequency or its second harmonic in the presence of a magnetic field. The signatures of these different modes of the detuned probe light beam polarization fluctuations, observed either as Faraday rotation noise or as ellipticity noise, are shown to depend dramatically on the probed transition. In particular, depending on the Zeeman structure of the upper level of the transitions, the different noise modes can be visible or not, and their dependence on the probe polarization can be completely modified. Those predictions are successfully compared with measurements of spin-noise signals using three different transitions of an ensemble of metastable $^{4}\mathrm{He}$ at room temperature.

Two-dimensional Thouless pumping of light in photonic moiré lattices

Continuous and quantized transports are profoundly different. The latter is determined by the global rather than local properties of a system, it exhibits unique topological features, and its ubiquitous nature causes its occurrence in many areas of science. Here we report the first observation of fully-two-dimensional Thouless pumping of light by bulk modes in a purpose-designed tilted moiré lattices imprinted in a photorefractive crystal. Pumping in such unconfined system occurs due to the longitudinal adiabatic and periodic modulation of the refractive index. The topological nature of this phenomenon manifests itself in the magnitude and direction of shift of the beam center-of-mass averaged over one pumping cycle. Our experimental results are supported by systematic numerical simulations in the frames of the continuous Schrödinger equation governing propagation of probe light beam in optically-induced photorefractive moiré lattice. Our system affords a powerful platform for the exploration of topological pumping in tunable commensurate and incommensurate geometries.

Signal of an autocorrelation low-coherence interferometer probing a layered object by a wave-field with wide angular spectrum

The effect of the width of the angular spectrum (numerical aperture) of a broadband-frequency wave-field probing a layered object on the signal of an autocorrelation low-coherence interferometer (ALCI) under spatially coherent and incoherent illumination of the entrance pupil is considered. It is found that under incoherent illumination an increase in the width of the angular spectrum of the field leads to a decrease in the amplitude, a change in the shape and position of the measuring signals of the interferometer due to decorrelation of the object field partial components which have reflected from various interlayer boundaries inside the object. In the case of coherent illumination, the ALCI signal is formed in a confocal mode, which leads to the amplitude extraction of the measurement signals are determined by the mutual correlations between a partial component reflected from the boundary on which the probing field was focused, and partial components of this field which have reflected from other boundaries within the object. This effect makes it possible to determine parameters of the internal layered structure of an object doing without apriori structure-related information. In this case, an increase in the numerical aperture of the probing light beam leads to an increase in the systematic error in determining the optical thicknesses of the layers, which can be estimated on the basis of the obtained expressions.

Theoretical Study of Spatial and Angular Goos-Hänchen Shifts in Quantum System

The behavior of the spatial and angular Goos-Hanchen (GH) shifts for the reflected and transmitted probe light beams is theoretically investigated in a fixed geometrical configuration containing the three and then four – level quantum dot nanostructure. It is found that, by adjusting the controllable parameters such as Rabi frequencies of applied fields, the spatial and angular Goos-Hanchen shifts can be controlled containing both of the positive and negative shifts of reflected and transmitted probe light beams. Moreover, we find that the simultaneous superluminal or subluminal light reflected and transmitted probe beams can be obtained through the medium.

Data capacity scaling of a distributed Rydberg atomic receiver array

The data transfer capacity of a communication channel is limited by the Shannon–Hartley theorem and scales as log2(1+SNR) for a single channel with a given power signal-to-noise ratio (SNR). We implement an array of atom-optical receivers in a single-input-multi-output configuration by using spatially distributed probe light beams. The data capacity of the distributed receiver configuration is observed to scale as log2(1+N×SNR) for an array consisting of N receivers. Our result is independent of the modulation frequency, and we show that such enhancement of the bandwidth cannot be obtained by a single receiver with a similar level of combined optical power. We investigate both theoretically and experimentally the origins of the single channel capacity limit for our implementation.

Raman scattering model of the spin noise.

The mechanism of formation of the polarimetric signal observed in the spin noise spectroscopy (SNS) is analyzed from the viewpoint of the light scattering theory. A rigorous calculation of the polarimetric signal (Faraday rotation or ellipticity) recorded in the SNS is presented in the approximation of single scattering. We show that it is most correctly to consider this noise as a result of scattering of the probe light beam by fluctuating susceptibility of the medium. Fluctuations of the gyrotropic (antisymmetric) part of the susceptibility tensor lead to appearance of the typical for the SNS Faraday rotation noise at the Larmor frequency. At the same time, fluctuations of linear anisotropy of the medium (symmetric part of the susceptibility tensor) give rise to the ellipticity noise of the probe beam spectrally localized at the double Larmor frequency. The results of the theoretical analysis well agree with the experimental data on the ellipticity noise in cesium vapor.

Fiber fabric as an element of signal systems

The article presents research materials for developing fiber-optic sensors that can be integrated into items of clothing or combat equipment of servicemen. The geometric, mechanical and functional characteristics of the sensors can be varied depending on the purpose of the signal element, which allows their integration into textile materials, which are the basis for the manufacture of military equipment. Replacement of areas of textile fabric in places where it covers the optical sensor with fabric elements made of optical fibers has a multifunctional purpose. First, due to its tissue structure, it expands the probing light beam from a spot (with a spatial dimension of 0D) into a 2D scan, thereby improving the spatial sensitivity diagram of the sensor. Second, it replaces the removed tissue on top of the sensor, thereby restoring the integrity of the tissue. Third, it performs a protective and masking function for the sensor. In terms of strength, elasticity and durability, such fabric materials are almost indistinguishable from traditional ones. The paper experimentally demonstrates that the system of quasi-parallel fibers, which can be part of the fabric elements of clothing or equipment of a serviceman, plays the role of a diffraction grating for a laser beam. The shape of the diffraction band strongly depends on the angle of incidence of the light beam relative to the normal to the grating. The shape of the diffraction band is linear if the incident ray is in a plane perpendicular to the plane of the system of quasi-parallel optical fibers and at the same time perpendicular to the direction of the fibers. If the incident ray is outside this plane, then in the general case, the shape of the diffraction band is described by a second-order curve. The effect of curvature of the diffraction band when the laser beam falls obliquely on the lattice is a consequence of the so-called conical diffraction of light, in which the diffracted rays propagate along the surface of the cone. In particular, if the incident ray is in a plane perpendicular to the plane of the fiber system (grating) and parallel to the direction of the fibers, then depending on the angle between the incident ray and perpendicular to the grating plane, the diffraction band is a hyperbola at angles of incidence smaller than 45o, parabola, when the angle of incidence is 45o or ellipse at angles of incidence larger than 45o. The case of small angles of incidence when the diffraction band is a hyperbola is demonstrated in the work. The property of changing the type of the second-order curve (hyperbola / parabola / ellipse) of the diffraction band and its orientation (curved to the right / left or up / down) when changing the angle of incidence of the light beam on the grating can be used to determine the position of the light source (laser sniper sight) with respect to the fiber optic grating integrated into the item of clothing or equipment of the serviceman.

Wave Beams with a Fractal Structure, Their Properties and Applications: A Literature Review

Concepts of formation and propagation of radiation with a fractal amplitude–phase profile are analyzed and systematized on a single methodological basis using main points of fractal physics. Motion of a plane wave through fractal phase and amplitude screens is considered. Characteristics of beams with a stochastic and a regular self-similar structure are discussed. A range of questions on direct formation of waves with a fractal amplitude and phase distribution in laser systems is examined. The analysis shows that scaling characteristics complement the space–time parameters traditionally used for describing light beams. In particular, mutually complementing are statistical and fractal data on propagation of beams in the turbulent atmosphere. To date, the mathematical and physical apparatus has been developed that allows self-similar and scaling properties of radiation to be adequately described. With this apparatus, it is possible to develop efficient methods for optical diagnostics of fractal structures using probing light beams. A high degree of stability of Fourier images of fractals is an important factor for increasing stability and noise immunity of optical information transmission channels based on fractal beams.

Absorbance Detection in Multireflection Microfluidic Channels Using a Commercial Microplate Reader System.

Absorbance detection is often prohibited in microfluidic channels due to the limited optical path length available in these systems. However, this optical distance may be significantly increased by guiding the probing light beam along the channel length via multiple reflections by patterned metallic surfaces. In this work, we demonstrate enhanced absorbance detection in glass microfluidic channels using a commercial microplate reader based on this principle, yielding detection limits comparable to that measured on standard microwell plates. This improvement in detectability was realized through careful optimization of the mirror lengths and locations combined with the appropriate design of a microchip holder to suitably position the microchannels in the microplate reader. Additionally, it was determined that the angle by which our device was tilted relative to the horizontal plane played an important role in this optimization. For an optimum choice of parameters accessible with our design, the sensitivity of our absorbance measurements in a 30 μm-deep channel was improved by as much as 52-fold, raising this quantity to about 84% of the corresponding value realized for 75 μL samples placed within 7 mm i.d. standard cylindrical microwells. Quantitative ELISAs employing the absorbance detection method were demonstrated on the noted multireflection microchip device for assessing West Nile viral IgM antibody levels in human serum samples yielding analyte detection limits comparable to that measured on standard microwell plates.

Optical diagnostics fractal structures: methodical aspects

The properties of fractal structures defined by complex functions are tested. The amplitude-phase characteristics and spatial spectra of probing light beams are considered. An important methodic aspect of spectral analysis of structures with fractal geometry is the ability to expand the range of information obtained by parallel amplitude and phase processing. In deciphering the Fourier images of fractals, one can use the discovered fact that the intensity maxima and phase singularities coincide. As a positive point, it should be noted a high degree of the spatial spectrum stability to the influence of optical noise. The registered degree of asymmetry of the Fourier image structure can be used to determine the level of phase disturbances in the initial light field. The performed work expands the knowledge of factors requiring consideration in the optical diagnostics of fractal objects.

Manipulation of Goos–Hänchen shifts in a HCN→HNC isomerization with permanent dipole moments

The behavior of the Goos-Hanchen shifts of the reflected probe light beam at the interface of a three-layer cavity with a three-level Λ-type molecular system is theoretically investigated. The molecular system is HCN→HNC isomerization with nonzero permanent dipole moments (PDMs). The effect of electromagnetically induced transparency (EIT) induced by PDMs in molecules is studied for (1+1)- and (1+2)-transition processes. Thus, the optical response of the medium is modified by the quantum coherence due to nonzero PDMs. Moreover, the reflected probe light field for both transitions experiences superluminal light propagation. Goos–Hanchen shifts of the reflected probe light beam are substantially modified by the refractive index of the interactive medium as well as incident angle. The effect of the coherent coupling field intensity on absorption, dispersion, group index, and the Goos–Hanchen shifts of the reflected probe beam is also discussed.