Amplification Of Radiation Research Articles

Enhanced and tunable near-field thermophotovoltaics driven by hybrid polaritons

Near-field thermophotovoltaics (NF-TPV) offers the potential for achieving elevated power density and conversion efficiency by leveraging the amplification of thermal radiation within a nanoscale gap. Here, we propose an NF-TPV device with a sandwich emitter composed of calcite film and graphene layer. The results show that this sandwich configuration can significantly enhance output power, outperforming monolayer-graphene-covered heterostructures and the single calcite film. These are because the sandwich configuration can enhance hybrid polaritons, which are formed by the coupling between surface plasmon polaritons in graphene and hyperbolic phonon polaritons in calcite. In addition, the effects of graphene chemical potentials on the performance of NF-TPV devices are also studied. The tunable power density range of the sandwich structure can be up to 3.26 times that of other structures by altering the chemical potential of graphene. The findings presented here may unpack a promising path for enhancing and manipulating the performance of NF-TPV at the nano- and microscale.

LiNbO3:Ho3+ Crystal as a Material for Radiation-Balanced Lasing in the 640–670 nm Region

Holmium-doped congruent-composition lithium niobate (LiNbO3:Ho, LN:Ho) crystals were grown by the Czochralski method. The absorption of the LN:1at% Ho3+ crystal was recorded at room temperature. On the basis of the analysis of emission and absorption spectra of the LN:1at% Ho3+ crystal, the possibilities of obtaining, at room temperature, radiation-balanced (RB) lasing in the region of 640–670 nm wavelengths corresponding to the inter-Stark transitions of manifolds 5F5 and 5I8 was theoretically investigated. The RB lasing parameters were calculated and the optimal pump and laser wavelengths were determined: λOP=652.1 nm, λOL=653.6 nm. The values for the RB lasing efficiency and radiation amplification in the considered wavelength region were obtained: Feff=3.23×10−22cm2, Fgain=6.08×10−22 cm2.

Total cross-polarization conversion and polarization-sensitive amplification of terahertz radiation in graphene with direct electric current

Total cross-polarization conversion and polarization-sensitive amplification of terahertz radiation in graphene with direct electric current

Bismuth-Doped Fiber Lasers and Amplifiers Operating from O- to U-Band: Current State of the Art and Outlook

The development of unique optical materials that provide amplification and lasing in new wavelength ranges is a major scientific problem, the solution of which is becoming the basis for the emergence of new optical technologies, which are primarily targeting the expanding of operating wavelengths in silica glass. In fact, one of the notable advances in the field of fiber optics over the past two decades has been the production of a new type of laser-active fibers (namely bismuth-doped fibers), which has made it possible to cover previously inaccessible (for rare-earth-doped fibers) spectral ranges, in particular O-, E-, S-, and U-telecom bands. The advance in this direction has led to further growth of the technological capabilities in the telecom industry for amplification and generation of optical radiation in various wavelength bands, which will result in the near future to overcoming the problem known as “capacity crunch” by means of expanding the data transmission range. Recently, bismuth-doped fibers have been actively studying in order to improve their characteristics, which would allow for efficient implementation of optical devices based on bismuth-doped fibers (BDFs) with deployed telecommunications systems. This is one of the dynamically developing areas, where progress has already manifested in form of emergence of new achievements, in particular commercially available various types of BDFs, as well as a series of novel fiber-optic amplifiers for the O- and E-bands. In this review, a number of scientific studies that have already led to a noticeable progress in the field of optical properties of BDFs and the practical implementation of optical devices (lasers and amplifiers) based on them are presented and discussed, with much attention to the achievements of recent years.

Broadband amplification and thermal lensing in a combination of Yb:YLF and Yb:YAG crystals

Broadband amplification of laser radiation in a combination of Yb:YLF and Yb:YAG crystals was demonstrated. It was shown that, with the input spectrum width of 20 nm, the width at the output spectrum can reach 17 nm. A thermal lens induced in the Yb:YAG crystal is partially compensated by the lens in the Yb:YLF crystal due to the different signs of the ∂n/∂T coefficients of the crystals. The thermal lens in the Yb:YLF crystal in the thin and thick (“long-the-side pumped”) rod geometries was studied theoretically and experimentally. An analytical model of thermally induced phase distortions in uniaxial crystals caused by the piezo-optical effect was developed for the thin-rod geometry.

Planar Bilayer PT-Symmetric Systems and Resonance Energy Transfer

Parity-time (PT) symmetry provides an outstanding improvement of photonic devices’ performance due to the remarkable physics behind it. Resonance energy transfer (RET) as an important characteristic mediating the molecules that can be tailored in the PT-symmetric environment, too. We study how planar bilayer PT-symmetric systems affect the process of resonance energy transfer occurring in the vicinity thereof. First, we investigate the reflectance and transmittance spectra of such systems by calculating reflection and transmission coefficients as well as total radiation amplification as functions of medium parameters. We obtain that reflectance and total amplification are greatest near the exceptional points of the PT-symmetric system. Then, we perform numerical calculations of the RET rate and investigate its dependence on the complex permittivity of the PT-symmetric medium, dipole orientation, frequency of radiation and layer thickness. Optically thick PT-symmetric systems may operate at lower gain at the expense of the appearance of chaotic-like behaviors. These appear owing to the dense oscillations in the reflectance and transmittance spectra and vividly manifest themselves as stochastic-like positions of the exceptional points for PT-symmetric bilayers. The RET rate, being a result of the field interference, can be significantly amplified and suppressed near exceptional points exhibiting a Fano-like lineshape.

Improvement of the Destructive Interference Method in the Mitigation of PLC Radiation of Imbalanced Impedance Electrical Networks

Communication technology by power line carrier (PLC) marks its return with the advent of energy-mix. Although appreciated by power-grid operators and customers, this technology suffers from the emission of parasitic electromagnetic radiation. Suspected of causing heath problem, the future of this technology is linked to the level of its radiation reduction. This radiation, which is mainly due to the common mode current, can be attenuated by many ways such as the destructive interference method. The destructive interference method is a dynamic mitigation method mainly used on indoor PLC network. The mitigation of PLC radiation by this method gives reduction rates of more than 24 dB on a balanced impedance electrical network. Unfortunately, the effectiveness of this method decreases sharply depending on the level of network instability (impedance imbalance). This work focuses on improving the effectiveness of the destructive interference method on certain points of the network (point of weak mitigation or amplification of radiation) in an unstable environment. This improvement of the method is centered on the adaptation of the mitigation parameters (phase and amplitude) via a sequential mode of action. The positive impact of the improved method, although focused on a specific area, extended throughout the network. For a network with imbalanced impedance, the average rate of mitigation with this new method exceeds 11 dB.

Amplification of near field radiation at surfaces of pure dielectric domain with anti-reflection films and photonic crystal structures

With chemical stability under high temperatures, dielectric materials can be idealized thermal emitters for different energy applications. However, dielectric materials do not support surface waves at near-infrared ranges for longer-distance thermal photon tunneling, which limits their applications in near-field thermal radiation. It is demonstrated in this study that thermal field amplification at near-infrared wavelengths at dielectric surfaces could be achieved through asymmetric Fabry–Perot resonance with anti-reflection coatings or 1D photonic crystal type structures. ⩾100 nm near-infrared thermal photon tunneling can be achieved when these thin film structures are added to the emitter and the collector surfaces. Among these two thin film structures, 1D photonic crystal type periodic structures constructed with the same high refractive index material as the emitter/collector material allow near-field thermal photon tunneling at large parallel wavenumbers. Moreover, the field amplification can be increased by adding more 1D photonic crystal layers to achieve even longer distances near field thermal photon tunneling.

Terahertz amplification and lasing by using transverse electric modes in a two-layer-graphene-dielectric waveguide structure with direct current

We study for the first time the interaction between the waveguide modes of graphene structure and freely propagating terahertz (THz) electromagnetic waves (this interaction takes place within the light cone). We revealed a new and rather unexpected physical phenomenon by showing that freely incident THz electromagnetic waves can resonate with the surface transverse electric (TE) modes of the graphene waveguide in virtue of these modes having their dispersions in the vicinity of the light cone. The dispersion and amplification of surface TE modes in a dielectric waveguide covered with two graphene layers biased by direct current (DC), as well the amplification and lasing of incident THz wave by excitation of TE mode resonances, are investigated. The DC flows perpendicular to the direction of the surface wave propagation and creates the capacitive complex conductivity of graphene at THz frequencies, which is necessary for the existence of surface TE modes in graphene. The real part of graphene conductivity can be negative at THz frequencies due to DC in graphene which leads to amplification and lasing of THz radiation. Such structure can be of great practical importance because an external THz wave can be amplified or generated in lasing process without using special coupling elements commonly needed for ensuring the interaction between external THz wave and surface waveguide modes. The use of a two-layer graphene structure makes it possible to reduce the charge–carrier drift velocity required for reaching the lasing threshold at those resonances, as compared to a structure with a single graphene layer.

Coherent amplification of radiation from two phase-locked Josephson junction arrays.

We analyze experimentally and theoretically mutual phase locking and electromagnetic interaction between two linear arrays with a large number of Josephson junctions. Arrays with different separation, either on the same chip or on two separate substrates are studied. We observe a large coherent gain, up to a factor of three, of emitted power from two simultaneously biased arrays, compared to the sum of powers from two individually biased arrays. The phenomenon is attributed to the phase locking of junctions in different arrays via a common electromagnetic field. Remarkably, the gain can exceed the factor of two expected for a simple constructive interference of two oscillators. The larger gain is explained by an additional consequence of mutual interaction between two large arrays. Mutual phase locking of large arrays does not only result in constructive interference outside the arrays, but also improved synchronization of junctions inside each array. Our conclusion is supported by numerical modelling.

Transit-time resonances enabling amplification and generation of terahertz radiation in periodic graphene p-i-n structures with the Zener–Klein interband tunneling

The Zener–Klein (ZK) interband tunneling in graphene layers (GLs) with the lateral n-i-n and p-i-n junctions results in the specific characteristics that can be used for the rectification, detection, amplification, and generation of the terahertz (THz) signals. The transit-time delay of the tunneling electrons and holes in the depletion regions leads to the phase shift between the THz current and THz voltage causing the negative dynamic conductance in a certain frequency range and resulting in the so-called transit-time (TT) instability. The combination of the ZK tunneling and the TT negative dynamic conductance enables resonant THz the amplification and generation of THz radiation. We propose the THz devices based on periodic cascade GL p-i-n structures exhibiting the TT resonances and evaluate their potential performance. Such structures can serve as THz amplifiers and, being placed in a Fabry–Pérot cavity, or coupled to a THz antenna or using a ring oscillator connection, as THz radiation sources.

Amplification of laser radiation at the edge of the KrF (B–X) spectral line

We report the results of experimental and numerical studies of the KrF electric discharge amplifier operating on a mixture of He – Kr – F2 gases. The possibility of expanding the short-wavelength spectral region of the induced radiation tuning at the B – X transition of the KrF molecule by removing the inverse population from the upper vibrational states of the electronic B level is shown. It is demonstrated that at the boundary of the active medium gain contour, the measured gain at a wavelength of 246.8 nm is 0.053 cm−1. Using the developed 1D model of the KrF electric discharge amplifier, it is shown that when the active medium is excited by a pump pulse with a specific peak power of ∼10 MW cm−3, the gain in this spectral region is due to a longer relaxation time of the population of excimer molecules from the upper vibrational levels compared with the characteristic time of their production.

Rancang Bangun REFLECTOR Untuk Mengoptimalkan Daya Serap Matahari Pada Panel Surya Dengan Variasi Sudut Guna Menghasilkan Daya Optimal

Various kinds of treatments given to solar panels illustrate efforts to increase the output power of solar panels and the efficiency of solar cells. In the following research, we will analyze the differences in the output power and efficiency of solar cells that have received different treatments. In the solar panel that will be analyzed in this study is the addition of a reflector to solar cells with a reflector tilt angle of 90 ° and 60 ° as a form of variation of radiation amplification. The idea for the use of a reflector is to increase the yield of solar cell input radiation. After testing, the output power produced by solar cells increases as the radiation received by the solar panels increases and the efficiency of the solar panels decreases as the temperature of the solar cells increases.

Terahertz amplifiers based on gain reflectivity in cuprate superconductors

We demonstrate that parametric driving of suitable collective modes in cuprate superconductors results in a reflectivity $R>1$ for frequencies in the low terahertz regime. We propose to exploit this effect for the amplification of coherent terahertz radiation in a laser-like fashion. As an example, we consider the optical driving of Josephson plasma oscillations in a monolayer cuprate at a frequency that is blue-detuned from the Higgs frequency. Analogously, terahertz radiation can be amplified in a bilayer cuprate by driving a phonon resonance at a frequency slightly higher than the upper Josephson plasma frequency. We show this by simulating a driven-dissipative $U(1)$ lattice gauge theory on a three-dimensional lattice, encoding a bilayer structure in the model parameters. We find a parametric amplification of terahertz radiation at zero and nonzero temperature.

Enhancements in output properties of optical radiation in the range of 1650 nm using a dual-polarization Raman amplification method

Subject of study. Raman amplification of optical radiation in the wavelength range of 1650 nm in an extended optical fiber and enhancement in its effectiveness were investigated. Objective. The possibility of increasing the radiation output power of an individual Raman amplifier without degradation of its spectral properties was considered. Method. A method of independent amplification of two orthogonal radiation polarizations in an extended optical fiber is proposed, where depolarized input optical radiation is separated into radiation with two independent linear polarizations, which can interact with pump radiation more effectively. Each polarization of the input radiation is affected by a lower pump power, which results in a lower distortion of the output radiation under its amplification in an extended optical fiber. Main results. A scheme of dual-polarization amplification of optical radiation was mathematically modeled and realized. Linearly polarized radiation of a distributed feedback laser was split into two channels using a polarization splitter. Radiation propagated in each channel with mutually orthogonal polarizations. A “panda”-type fiber section was additionally introduced to one of the channels to eliminate mutual coherence of radiation. Both channels were merged by a polarization combiner and radiation was guided to preliminary and final Raman amplifiers. The nonlinear distortions of the output radiation of the Raman amplifier were compared for the cases of single- and dual-polarization amplifications. The nonlinear distortions at an output power of 3.5 W at the wavelength of 1650 nm were lower for the dual-polarization amplification, which ensures a narrower spectrum of the output radiation. A slightly higher nondistorted power of approximately 4 W was obtained in this mode at the specified wavelength without degradation of the spectral properties of the output radiation. Practical significance. The obtained results allow more powerful radiation sources in the wavelength range of 1650 nm to be developed for, e.g., lidars used for monitoring of greenhouse gases such as methane, carbon dioxide, or water vapor. This technology can also be used in other fields such as medicine and telecommunications.

Transmissive terahertz amplifier based on optically pumped graphene-dielectric hybrid resonators

Amplification of terahertz radiation is achieved by combining optically pumped graphene with a dielectric resonant cavity through numerical simulation. Graphene is attached to a one-dimensional grating and sandwiched between two distributed Bragg reflectors. The whole cavity enhances the interaction of graphene with the terahertz wave while being transparent to the pump light. When the femtosecond pulse pump light at 1.5 µm with the peak intensity of 8.7 W / m m 2 is considered, graphene is driven to a gain medium. Due to the enhancement of the cavity and the proper complex conductivity of graphene, the amplitude of the transmitted beam is amplified 172 times at 3.82 THz at room temperature, showing great potential in the development of terahertz amplifiers and even lasers.

Mechanical improvement in solar aircraft by using tangent hyperbolic single-phase nanofluid

Solar power is the primary thermal energy source from the sunlight. This research has carried out the study of solar aircraft with solar radiation in enhancing efficiency. The thermal transfer inside the solar aircraft wings using a nanofluid past a parabolic surface trough collector (PTSC) is investigated thoroughly. The source of heat is regarded as solar radiation. For several impacts, such as porous medium, thermal radiation, and varying heat conductivity, the heat transmission performance of the wings is examined. By using the tangent hyperbolic nanofluid (THNF), the entropy analysis has been performed. The modeled momentum and energy equations are managed using the well-established numerical methodology known as the finite difference method. Two distinct kinds of nano solid-particles have been examined, such as Copper (Cu) and Zirconium dioxide (ZrO2), while Engine Oil (EO) being regarded as a based fluid. Different diagram parameters will be reviewed and revealed as figures and tables on speed, shear stress, temperature, and the surface drag coefficient and Nüselt number. It is observed that in terms of heat transfer for amplification of thermal radiation and changeable thermal conductance parameters, the performance of the aircraft wings raises. In contrast to traditional fluid, nanofluid is the best source of heat transmission. Cu-EO's thermal efficiency over ZrO2-EG falls to the minimum level of 12.6% and has reached a peak of 15.3%.

Radiation from a charge drifting along a cylindrical channel

Radiation of a charged particle moving in a cylindrical channel with elastic walls is studied. We assume that the particle in the channel is in free motion, periodically colliding with the channel wall. Explicit expressions for the spectrum and angular distribution of radiation are obtained. These results can be used to calculate the spectrum and radiation intensity of charged particles in carbon nanotubes of relatively great diameter. The emission spectrum is essentially a bremsstrahlung one, however, periodic collisions of the particle with the wall lead to coherent amplification of radiation at frequencies that are multiples of the collision frequency. If a beam of particles is channeled, then the multiple spectral lines merge into a continuous spectrum.

Thermal capability and entropy optimization for Prandtl-Eyring hybrid nanofluid flow in solar aircraft implementation

In addition to photovoltaic cells, solar power plates, photovoltaic lights, and solar pumping water, solar energy is the primary source of heat from the sun. At the moment, researchers are looking at the use of nanotechnological and solar radiation to increase aeronautical efficiency. In this study, hybrid nanofluid flow linearly passes through a parabolic trough solor collector (PTSC) on the interior of solar aircraft wings to study heat transmission. Solar radiative flow was the term used to describe the heat source. The heat transfer efficiency of the wings is evaluated for several effects, such as a slanted magnetic field, viscous dissipation, play heating, and thermal radiative flow. Entropy generation study was performed on the Prandtl-Eyring hybrid nanofluid (P-EHNF). The Keller box technique was used to solve the predicted energy and momentum equations. As a typical fluid, EG (ethylene glycol) is used to disperse the nanosolid particles, which consist of copper (Cu) and cobalt ferrite (CoFe2O4). A variety of control factors, including velocity, shear stress, and temperature outlines as well as a frictional factor and Nusselt number, are addressed in detail. Thermal radiation amplification and variable thermal conduction parameters appear to increase the efficiency of aircraft wings in terms of thermal transfer. Hybrid nanofluid is superior to conventional nanofluid in terms of heat transmission. Cu-EG has a low thermal efficiency between 3.8% and 4.8% than CoFe2O4-Cu/EG nanofluid.

Magnetic turbulence in supernova remnants: perspective for IXPE polarimeter

Supernova remnants (SNRs) are well known sources of the non-thermal radiation, particle acceleration and magnetic field generation and amplification. Synchrotron radiation of the accelerated electrons in the magnetic field is an important emission mechanism in SNRs that can dominate in radio and X-ray energy bands. Turbulent magnetic field yields to formation of the special inhomogeneous (clumpy) structure in the SNR synchrotron X-ray images. This structure could differ significantly on the SNR polarization maps for different types of the magnetic turbulence. A new family of the gas pixel detector X-ray polarimeters that are supposed to have good sensitivity and angular resolution should be well suited for SNR polarimetry. IXPE (NASA) will be the first polarimeter of this kind. Lately a model IXPE synchrotron polarization images of Tycho SNR were simulated in the 3 — 8 keV energy band. It was shown that IXPE observation time of ~ 1 Ms should be enough to distinguish characteristic features that are specific for some types of the magnetic turbulence. We perform simulations of Tycho SNR polarization maps for a wider set of energy bands in order to determine the most suitable energy range for study of the SNR turbulent magnetic field using IXPE. The dependence of the polarization degree on the photon energy is accurately considered in the simulations. IXPE background influence on the observations of Tycho SNR is also discussed here together with possible ways of data processing and interpretation reducing this effect.