Values Of Detuning Research Articles

Noise-resistant multi-frequency phase local radionavigation system based radio interference transmitters

Formulation of the problem. The widespread use of electronic warfare has led to significant difficulties in the use of consumer navigation equipment (CNE) of global navigation satellite systems (GNSS). Local radio navigation systems, alternatives to GNSS, are characterized by low accuracy and low noise immunity. At the same time, a spatially distributed system of radio interference transmitters CNE GNSS, using wide-band multi-frequency BPSK signals, can be used to organize a noise-resistant LRNS, in which phase measurements will be used to increase the accuracy of measurements. Purpose. The purpose of this work is to justify the requirements for a local radio navigation system based on spatially distributed radio interference transmitters NAP GNSS, using the noise-resistant method of multi-frequency phase radio navigation. Results. An interference-resistant method of multi-frequency phase radio navigation is presented, and the requirements for a local radio navigation system based on this method are substantiated. For the given typical characteristics of NAP GNSS radio interference transmitters, the value of the frequency detuning of the spectral components of the multi-frequency signal was obtained, at which the best positioning accuracy is achieved. Practical significance. The results obtained can be used to organize a noise-resistant multi-frequency phase local radio navigation system based on NAP GNSS radio interference transmitters.

Tripartite entanglement in a detuned non-degenerate optical parametric oscillator

Continuous variable multipartite entanglement is an important resource in quantum optics and quantum information. Non-degenerate optical parametric oscillator (NOPO), generally working in a resonant regime, can generate high quality tripartite entanglement. However, the detuning in a real experiment is inevitable and sometimes necessary, for instance, in an optomechanical system. We calculate the tripartite entanglement from a detuned triply quasi-resonant NOPO. Unlike the previous literature using inseparability criterion, we use the positivity of partial transpose, a sufficient and necessary criterion, to characterize the tripartite entanglement with full inseparability generated from a detuned NOPO. We also consider the influence of the pump and signal/idler losses on the tripartite entanglement. The results show that, the tripartite entanglement could exist even with a large detuning of several times cavity linewidth, and may be better for a detuned regime than for the resonant one under some conditions. With a fixed non-zero loss which always exists in a real experiment, an appropriate value of non-zero detuning could lead to the best entanglement. What’s more, unlike the bipartite entanglement, which exists both below and above threshold, the tripartite entanglement only occurs for a nonzero classical amplitude of signal/idler field. The jumping between the tripartite and bipartite entanglement could make the NOPO become a quantum state switch element, which promises a potential application on the multiparty quantum secret sharing.

Distant bipartite entanglement generation in a hybrid opto-magnomechanical system

In this work, we present a hybrid cavity opto-magnomechanical system to generate distant bipartite entanglement between different quantum carriers. Accordingly, the system consists of two cavity photons, a phonon of yttrium iron garnet (YIG), a magnon, and a phonon of membrane. Specifically, the two cavities are coupled through an optical fiber, and one of the optical cavities consists of a membrane coupled with the cavity photon through radiation pressure force. While the other cavity contains a YIG, the magnon mode connects to the cavity photon via magnetic dipole interaction and, simultaneously, couples to the mechanical resonator of the YIG through magnetostrictive interaction. We show that entanglement generation can be realized under indirectly coupled bipartitions for parameters and detunings within appropriate regimes. Furthermore, for various bipartitions, we also obtain appropriate cavity and magnon detuning values for a considerable remote entanglement. Moreover, the generation of distant bipartite entanglements and entanglement transfer between subsystems is predominantly influenced by the coupling strength. Remarkably, the distant bipartite entanglement is strongly contrary to the environmental temperature. Thus, optimizing the system’s parameters allows for the maximum possible entanglement between various quantum carriers. We believe our results could provide more stable bipartite entanglements and serve as a potential quantum interface to realize particularly long-range entanglement transfers.

Coherent control of parametric generation of laser beams via intersubband transitions in quantum wells

This paper investigates the propagation dynamics of laser beams within a semiconductor quantum well (QW) system. The study explores various scenarios involving different detuning values and spatially varying incident beams. The light–matter interaction within the QW system shows a complex interplay between detuning, spatial characteristics, and beam properties. In the resonant case, where the detuning values for probe and signal beams are zero, we observe exponential relaxation of both beams reaching a common value. Introducing detuning leads to oscillatory behaviors, with larger detuning values promoting more pronounced oscillations and an enhanced signal beam. The investigation takes an intriguing turn when we consider position-dependent incident beams. In these cases, the spatial patterns of the initial beam are transferred to the generated beam, leading to soliton-like propagation and the creation of beams with specific spatial dependencies. Remarkably, under substantial detuning, both incident and generated beams adopt periodic patterns in two dimensions, forming lattice structures with spot-like peak intensities. These findings underscore the versatility and controllability of the QW system, offering opportunities for engineered spatial and spectral properties in laser beams.

Effectively modulating spatial vortex four-wave mixing in a diamond atomic system

Due to the spatial characteristics of orbital angular momentum, vortex fields can be applied in the fields of quantum storage and quantum information. We study the realization of spatially modulated vortex fields based on four-wave mixing in a four-level atomic system with a diamond structure. The intensity and spiral phase of the vortex field are effectively transferred to the generated four-wave mixing field. By changing the detuning of the probe field, the phase and intensity of the generated vertex four-wave mixing field can be changed. When the probe field takes a large detuning value, the spatial distribution of the intensity and phase of the vertex four-wave mixing field can be effectively tuned by adjusting the Rabi frequency or detuning value of the coupled field. At the same time, we also provide a detailed explanation based on the dispersion relationship, and the results agree well with our simulation results.

Квазиправдоподобный алгоритм оценки частоты сверхширокополосного квазирадиосигнала с неизвестной длительностью

The quasi-likelihood frequency estimation algorithm of an ultra-wideband quasi-radio signal with an unknown duration, observed with white Gaussian noise, is studied. When synthesizing the frequency estimation algorithm, instead of an unknown duration, some of its expected value was used. The dependence of the variance of the frequency estimate of an ultra-wideband quasi-radio signal on the signal-to-noise ratio for various values of the duration detuning and the dependence of the frequency estimate bias on the duration detuning for various values of the narrowband parameter are obtained. It has been established that the duration detuning has a significant effect on the efficiency of frequency estimation of an ultra-wideband quasi-radio signal, while at large values of the narrowband parameter, the obtained expressions coincide with the known expressions for the variance and bias of the frequency estimate of narrowband radio signal. Recommendations on the use of the synthesized algorithm in practical applications are formulated.

Depiction of an external classical field effects on a four-level W-configuration atom embedded in a coherent cavity field

This paper examines the dynamics of a W-configuration four-level atom in a quantized cavity field and the system driven by an external classical field. By applying some canonical transformations, we derive analytical solutions to the Schrödinger equation for the corresponding Hamiltonian. We have analyzed the impact of the external field and detuning parameters on the system’s relative entropy of coherence, Wigner function, and Pancharatnam phase. Our findings suggest that the external field parameter greatly affects the coherence of the system, whereas the detuning parameters may increase its maximum bounds. Furthermore, we have utilized the Wigner function as a tool to measure the quantumness and classicality of the system in its phase space. Our results indicate that the external field has a greater impact on the classicality of the system than the detuning parameters. Additionally, we have observed rapid oscillations in the dynamics of the Pancharatnam phase for large detuning values. It is worth noting that the external field reduces the number of phase jumps in the system.

Peculiarities of exciton formation in 2D semiconductor nanostructures induced by quantum electromagnetic field under nonlinear self-phase modulation

Specific features of the excitation of a 2D semiconductor nanosystem by non-classical light in a solid state micro-resonator are found under the impact of the Kerr phase nonlinearity in the cavity. Different regimes of excitation are revealed in dependence on the efficiency of the nonlinearity. A negative impact of the nonlinear self-phase modulation on the excitation is found to be compensated by proper choice of the field frequency detuning. The possibility to controllably enhance a certain excitation channel by varying field frequency detuning is demonstrated and the value of the optimal detuning is found analytically. The effect of transfer of non-classical features from the field to the electronic subsystem is revealed. The formation of the photon-like non-classical excitonic states is demonstrated. The obtained results seem to be a basis for the creation of the light–matter interface and development of quantum information algorithms in solid state nanosystems.

Performance Analysis of Learning-Based Disturbance Observer for Pulsed Superconducting Cavity Field Control

The use of Disturbance Observer-based (DOB) control is widespread in stabilizing the electromagnetic field in superconducting radio frequency cavities to facilitate beam acceleration in particle accelerators. Repetitive disturbances such as beam loading and Lorentz force cavity detuning are compensated by DOB control, and their suppression is enhanced through the incorporation of a learning scheme into the conventional disturbance observer. This paper evaluated the performance of a learning-based disturbance observer for compensating beam loading and cavity detuning in pulsed superconducting radio frequency cavities and proposes modifications for better field stability. A superconducting cavity baseband model for π-mode was simulated in Matlab/Simulink with a trapezoidal beam pulse as the input disturbance and different cavity detuning values to analyze the controllers’ performance. The simulations were conducted for multiple observer filter bandwidths to evaluate the performance of the learning-based disturbance observer under plant model uncertainties and different detuning values. The results demonstrate that the learning-based disturbance observer yields faster convergence to the reference input and lower tracking errors during the flat top of pulse voltage in comparison to conventional disturbance observer control.

Quantum parametric double Raman oscillators with co- and counterpropagating fields: Relative intensity squeezing and spatial photon correlations

We present a comprehensive study of co- and counterpropagating Stokes and anti-Stokes quantum fields in double Raman four-wave mixing parametric oscillators using full quantum Heisenberg-Langevin framework with noise operators. General analytical solutions of the fields operators at any point in the Raman medium are obtained for four cases: two possible copropagating (forward) and two counterpropagating (backward) Stokes and anti-Stokes. We analyze the symmetrical properties of the complex linear and nonlinear susceptibilities spectra of the quantum fields, nonclassicality of two-photon correlation functions, spatial variations of the quantum fields, and the two-mode relative intensity squeezing. We compare the results of forward and backward cases for several limiting double Raman schemes. We find interesting resonant effects of medium length, laser detunings and laser field strengths (Rabi frequencies) for backward-propagating geometries. Analysis of the solutions provide insights on the resonant conditions while computation over multiple variables enables us to identify the values of laser detuning, field strength, and propagation length that give enhanced nonclassical intensity squeezing and persistent correlations. The present work sets the crucial foundations for optimization of the nonclassicality of photons in double Raman systems and would be useful for quantum information storage, quantum nonlinear optics, and quantum spectroscopy.

A Pulse Density Modulation Based Receiver Reactance Identification Method for Wireless Power Transfer System

Tuning the receiver to match the resonant frequency with the working frequency plays an important role in improving the efficiency. One of the crucial steps in tuning is to determine the value or degree of detuning. In order to obtain the receiver reactance used to determine the detuning value, this article proposes a pulse density modulation (PDM)-based receiver reactance identification method. The parameter identification is performed as follows: implementing PDM technology on the active single-phase rectifier (ASPR) to bring in interharmonics and through Fast Fourier Transformation and least-square approximation, values of inductor and capacitor of the receiver can be identified. This estimation method only requires the magnitudes of voltage and current into ASPR for estimation. No extra hardware, no need to synchronize with the transmitter. In the experimental verification, four cases of resonant, inductive, and capacitive receivers are designed. Results show the maximum relative errors for estimation are within 5%, based on which the ASPR can tune the receiver as resonant. The situation that parameter deviates from the nominal value is also considered, even with deviations of mutual inductance and transmitter-side reactance, the estimation accuracy of receiver-side reactance is still at an average level.

Stimulated Raman scattering induced dark pulse and microcomb generation in the mid-infrared

We demonstrate that strong stimulated Raman scattering in silicon and germanium microresonators can induce stable and breathing dark pulses generation circumventing traditional complex approaches such as pump modulation and mode coupling. Although multi-photon absorption shows a small influence on the detuning value for stable dark pulse excitation, the concomitant free carrier will assist dark pulse excitation and broaden the excitation area of dark pulse thus making it easier to capture stable pulse. Furthermore, dark breather dynamics in Si and Ge are also observed, which shows distinct properties from the dark soliton breathers dominated solely by Kerr effect. Finally, we show that octave spanning mid-infrared (MIR) microcomb can be generated combining with high-order dispersion engineering, which in turn affects the breathing dynamics of dark pulses. Our findings provide another way for the initiation of dark pulses in group IV materials and broadband MIR microcomb generation for spectroscopy applications.

Cascade Brillouin Lasing in a Tellurite-Glass Microsphere Resonator with Whispering Gallery Modes.

Brillouin microlasers based on microresonators with whispering gallery modes (WGMs) are in high demand for different applications including sensing and biosensing. We fabricated a microsphere resonator with WGMs from a synthesized high-quality tellurite glass with record high Q-factors for tellurite microresonators (Q ≥ 2.5 × 107), a high Brillouin gain coefficient (compared to standard materials, e.g., silica glasses), and a Brillouin frequency shift of 9 ± 0.5 GHz. The high density of excited resonance modes and high loaded Q-factors allowed us to achieve experimentally cascade Stokes-Brillouin lasing up to the 4th order inclusive. The experimental results are supported by the results of the theoretical analysis. We also theoretically obtained the dependences of the output Brillouin powers on the pump power and found the pump-power thresholds for the first five Brillouin orders at different values of pump frequency detuning and Q-factors, and showed a significant effect of these parameters on the processes under consideration.

Quantum coherence induced by a flux qubit coupled by a resonator coherent field through a two-photon interaction

The intrinsic decoherence effects on a flux qubit coupled to a resonator through a two-photon interaction where the resonator field is initially in coherent and even coherent states are investigated. The qubit-resonator entanglement and coherence loss (mixedness) of the system and its subsystems are examined using entropy and negativity. The ability of the qubit-resonator interaction to generate quantum coherence (qubit-resonator entanglement and mixedness) is shown to be dependent on the initial cavity non-classicality, detuning, and decoherence. For larger values of the qubit-resonator detuning, the initial resonator non-classicality can enhance the generation and stability of quantum coherence. The decoherence degrades the qubit-resonator entanglement and destroys the sudden death-birth entanglement.

Interwave interaction in an array of carbon nanotubes with a dynamic plasmon lattice

It is shown that when counterpropagating laser beams are incident on an array of parallel single-walled carbon nanotubes, strong interaction of waves is possible, accompanied by the amplification of one of the waves at the expense of another, more intense pump wave. The interaction is most efficient when the condition of phase matching of the incident waves and the slow plasmon polariton wave formed because of the laser-induced metallisation of nanotubes is satisfied. The dependence of the the signal wave gain on the geometric parameters of the array and the wave characteristics of the incident waves is studied numerically. A range of phase detuning values is found, in which the gain changes weakly near its maximum value.

A tunable autocorrelator for pulse measurements at IR FEL-oscillator facilities

Radiation characteristics of a Free-Electron Laser (FEL) such as pulse length, time structure, intensity, bandwidth, wavelength, power, frequency, etc., which were measured on a diagnostics table, are thoroughly discussed. In this respect, pulse length measurements of an Infrared FEL (IR-FEL) beam are evaluated through an intensity autocorrelator, designed and installed as a diagnostics tool at the “Helmholtz-Zentrum Dresden-Rossendorf (HZDR)-Radiation Source ELBE” of Germany. In addition, the autocorrelator was designed as a unique, cost-effective, and in-house setup. It operates within the wavelength range of 3–35 microns, using Cadmium-Telluride (CdTe) crystals in the Second Harmonic Generation (SHG) medium. The intensity autocorrelation curves were obtained for the FEL beam with the wavelength of 26.2 microns, indicating an FWHM pulse duration ranging between 3.29–8.03 ps with different optical cavity detuning values. Furthermore, the pulse duration of Ti: sapphire laser beam is measured between 1–3 ps through the designed autocorrelator at the ELBE light source. On the other hand, the setup may pave the way for pulse length measurements of the Turkish infrared FEL-oscillator facility (TARLA) as well, which is currently under the hardware installation phase. Finally, it is elaborated in section 3 that the unique autocorrelator design fully meets all requirements for pulse length measurements of an infrared FEL source.

Monolayer molecular sensing using infrared leaky waveguide mode

Surface-enhanced infrared absorption spectroscopy is attractive for molecular sensing due to its access to chemical bonds with high detection sensitivity. Such a spectroscopic method typically operates on localized resonances in subwavelength structured antennas and metamaterials. In this paper, we demonstrate monolayer octadecanethiol detection by using the leaky guided mode in a metal–insulator–metal waveguide, whose angle-tunable dispersion enables coupling to molecular vibrations with a frequency-variable optical resonance. Our results show that, by changing the incident angle from 15° to 75°, the resonance frequency of the leaky guided mode is scanned around the CH2 vibration modes with frequency detuning from −200 cm−1 to 350 cm−1 in wavenumber. As the frequency detuning increases, the vibration signal of both the CH2 symmetric and asymmetric modes increases first and then decreases. The maximum vibration signal of 1%–1.5% is reached at positive and negative frequency detuning values of ±100 cm−1. These sensing properties are explained with a coupled-oscillator model, which suggests that both enhanced near-field and coupling strength between the optical resonance and molecular vibration play an important role for the optimal sensing performance.

A METHOD FOR IMPROVING THE QUALITY INDICATORS OF A DISTRIBUTED FORENSIC INFORMATION SYSTEM

Subject of research: the process of monitoring the quality indicators of a computer network of a forensic information system using methods for increasing the frequency resolution of acousto-optic spectrum analyzers. The aim of this work is the possibility of increasing the QoS indicators of a computer network by achieving the potential accuracy of estimating the frequencies of two simultaneously arriving radio pulses using the super-Rayleigh resolution method in acousto-optic spectrum analyzers (AOSA). The following tasks are solved in the article: analysis of various information systems of forensic examination and the tasks that they solve; analysis of the use of acousto-optic spectrum analyzers to determine the parameters of the transmitted signal in a distributed forensic system; derivation of an analytical expression for evaluating the potential accuracy of the frequency detuning value of two pulses. The following methods and models are used: models and methods of systems theory (based on the information approach), models and methods for constructing distributed systems and their components in accordance with various hierarchical levels of their organization and operating conditions; models and methods of theories of propagation and interaction of electromagnetic waves with wave structures of various physical nature. The following results were obtained: The analysis has established that forensic information systems are distributed in nature and impose high requirements on the quality of the functioning of telecommunications equipment of the corresponding computer networks (CN). To meet these requirements, it is necessary to improve the systems for monitoring, protecting and transmitting information in the corresponding CN, which is impossible without solving the problem of monitoring signal parameters. Research has been carried out on the use of AOSA to ensure control over communication channels of computer networks. It was found that most of the AOSA frequency resolution methods have limitations associated with the Rayleigh criterion, which significantly limits the potential for frequency separation of pulses. The use of the method of super-Rayleigh resolution of narrow-band pulses in terms of their arrival time is proposed. An analytical expression is obtained to estimate the potential accuracy of determining the value of the detuning in the frequency of two pulses. Conclusions. The forensic information system is a complex heterogeneous distributed system. To improve the efficiency of its functioning, it is necessary to control the parameters of the signal propagating in the network. The use of the super-Rayleigh resolution method in AOSA will increase the resolution of AOSA by increasing the frequency resolution of two non-simultaneous radio pulses of long duration.

Effect of Damping on Magnetic Induced Resonances in Cross Waveguide Structures

We consider, in the frame of long-wavelength Heisenberg model, a simple magnetic device consisting of two dangling side stubs grafted at the same site along a waveguide. This simple structure is designed to obtain bound in continuum (BIC) modes, magnonic induced transparency (MIT) and magnonic induced absorption (MIA), the analogues of electromagnetic induced transparency (EIT) and absorption (EIA) resonances respectively. By detuning the lengths of the two stubs, a resonance can be squeezed between two transmission zeros induced by the two resonators. We give detailed analytical expressions for the transmission and reflection coefficients as well as the absorption coefficient of the whole structure. A sharp peak with high Q factor is found as the consequence of the constructive interference of the waves in the two stubs. For some specific detuning values, the Q factor may reach infinity giving rise to the so-called bound in continuum state. Also, we give several explicit expressions for other physical characteristics, e.g., the transmission function close to the resonance, the position, the width and the Fano parameters of the resonances as a function of the difference between the lengths of the stubs. The reported analytical results are obtained by means of a Green’s function method. These results should have important consequences for designing a selecting or rejecting magnon filter.

Off-axis optical vortices using double-Raman singlet and doublet light-matter schemes

We study the formation of off-axis optical vortices propagating inside a double-Raman gain atomic medium. The atoms interact with two weak probe fields as well as two strong pump beams which can carry orbital angular momentum (OAM). We consider a situation when only one of the strong pump lasers carries an OAM. A particular superposition of probe fields coupled to the matter is shown to form specific optical vortices with shifted axes. Such off-axis vortices can propagate inside the medium with sub- or superluminal group velocity depending on the value of the two-photon detuning. The superluminal optical vortices are associated with the amplification as the energy of pump fields is transferred to the probe fields. The position of the peripheral vortices can be manipulated by the OAM and intensity of the pump fields. We show that the exchange of optical vortices is possible between individual probe beams and the pump fields when the amplitude of the second probe field is zero at the beginning of the atomic cloud. The model is extended to a more complex double Raman doublet interacting with four pump fields. In contrast to the double-Raman-singlet, now the generation of the off-axis sub- or superluminal optical vortices is possible even for zero two-photon detuning.