查看更多>>摘要：We develop a quantum mechanical method of measuring the Newtonian constant of gravitation,. In this method, an optomechanical system consisting of two cavities and two membrane resonators is used. The added source mass would induce the shifts of the eigenfrequencies of the supermodes. Via detecting the shifts, we can perform our measurement of . Furthermore, our system can features exceptional point (EP) which are branch point singularities of the spectrum and eigenfunctions. In the paper, we demonstrate that operating the system at EP can enhance our measurement of . In addition, we derive the relationship between EP enlarged eigenfrequency shift and the Newtonian constant. This work provides a way to engineer EP-assisted optomechanical devices for applications in the field of precision measurement of .
Rameez-ul-IslamSaeed, Muhammad HaroonAwan, HiraImran, Muhammad...
8页
查看更多>>摘要：The past of a Quantum particle and the investigations of the particle's unitary evolution in between two strong measurements have generated a heated debate recently in quantum foundational context mainly studied earlier through photonics techniques. We, however, here propose an atom interferometric exploration based on the time tested tools of Atomic Bragg Diffraction to study the past of an atom, more akin to a real, concrete particle as compared with its counterpart i.e. photon. Two-State Vector Formalism (TSVF) along with the methodology of weak measurement have been invoked for the analysis of the past of an atom traversing a Mach-Zehnder Bragg atom interferometer and the results obtained are quite interesting. It is also being demonstrated explicitly that the suggested schematics are inherently deterministic and the proposal can be experimentally executed with high enough fidelity under the prevailing atom-field interaction based laboratory tools.
查看更多>>摘要：Recently, generalized fading distributions have gained substantial research interest due to their applicability and adaptability in practical scenarios. In this paper, we derive the exact closed-form expressions for the probability density function (PDF) and cumulative distribution function (CDF) of the maximal-ratio combining (MRC) of the free space optics (FSO) and radio frequency (RF) links over the most generalized Malaga and alpha-eta-kappa-mu fading models. Further, with the help of derived MRC channel statistics (i.e. PDF and CDF), closed-form expressions for outage probability and average symbol error rate (SER) for the hybrid FSO/RF system based on MRC and adaptive combining schemes are derived. In an adaptive combining scheme, the MRC of FSO and RF links is employed at the receiver, if the operating FSO link quality is unacceptable for transmission. Further, the derived expressions are unified for both intensity modulation/direct detection (IM/DD) and heterodyne detection (HD) techniques. We have considered the effects of atmospheric path loss, atmospheric turbulence-induced fading and non-zero boresight pointing errors in case of the FSO link. We have also determined the optimum switching threshold and beam waist values for the adaptive combining scheme to achieve optimal performance. Moreover, computationally less complex asymptotic expressions are calculated and the diversity gains of MRC and adaptive combining schemes are determined. Finally, the performances of single-link FSO, hard-switching-based hybrid FSO/RF, MRC, and adaptive-combining-based hybrid FSO/RF systems are compared and the inferences are reported under various turbulence conditions, link distances, weather conditions, and severity of the pointing errors.
查看更多>>摘要：2D MoWS2 is fabricated by the chemical-vapor transport and liquid-phase exfoliation method. Its nonlinear optical response is measured. By using MoWS2 SA and EOM, an LD-pumped doubly Q-switched mode-locked (QML) Tm:YAP laser at 2 mu m waveband is presented. The average output power, the pulse width, and the pulse peak power of the Q-switched envelope are measured. In comparison to the singly QML laser with MoWS2 SA or EOM, the doubly QML laser can generate shorter pulse duration and higher peak power. Based on the fluctuation mechanism, a developed rate equation model under plane wave approximation is proposed to describe the doubly QML dynamic process. The pulse characteristics of QML laser are numerically simulated and the theoretical simulations are in agreement with the experiment results. Both the experiments and numerical simulations show that MoWS2 is a promising nanomaterial, and the dual-loss-modulated QML laser displays well performance in pulse width compression and peak power enhancement.
查看更多>>摘要：K- distribution plays a significant role in describing the statistics of the electromagnetic scattering with unique properties of random polarization characterized by the fluctuating Stokes parameters. Under the assumptions of K- distributed amplitudes for the contributing polarization phasors and a uniform distribution for the phase difference between two polarization components, we investigate the probability density functions of the Stokes parameters and study the development of polarization speckle when the number of steps in a random walk varies.
查看更多>>摘要：Different from the traditional radially polarized beams, the fractional order radially polarized beam possess the symmetry broken structure of the polarization state distribution. The symmetry broken of the optical beams' intrinsic structure can lead to the spin-orbit coupling of light. In this paper, we investigate the tight focusing of the fractional order radially polarized beam and show some interesting phenomena induced by the symmetry broken structure of the polarization state distribution. Firstly, the intensity and the spin angular momentum density are split in the focal plane, and the focal field intensity distribution can be controlled (split or focused) by modulating the initial phase of the polarization state. Furthermore, just like the spin angular momentum, the orbital angular momentum density also is split into two opposite parts (positive and negative). Though, the evolutions of the spin and the orbital angular momentum are different: as the change of the initial phase of the polarization state, the spin angular momentum distribution just is rotated slightly, yet the orbital angular momentum distribution is reversed. All these phenomena can be considered as the manifestations of the spin Hall effect of the fractional order radially polarized beam. Our results provide further potential applications of the vector beams in the focal field shaping.
查看更多>>摘要：In this paper, with the laser side irradiation of the NCFs, the forward scattering patterns can be obtained through the scattered spectra. Some characteristic values of the scattering patterns are introduced, and they correspond to the integral intensity of the electric field and are closely related to the azimuth. We proposed two methods to determine the azimuth of monolayer and bilayer NCFs, and the corresponding errors are less than 2 and 1, respectively. In addition, we discussed the influence of the structural parameters of the NCFs and the relative position of the screen, and the results show that the methods have universal applicability and screen position insensitivity. The methods can be applied to the online azimuth determination of the NCFs without damage and pollution to the NCFs.
查看更多>>摘要：Hole transfer layer-free perovskite solar cells (HTL-free PSCs) have been proposed to reduce manufacturing costs and improve stability. However, the weak optical absorption of the perovskite layer in the infrared region and ultrathin PSCs design have received less attention. In this study, ultrathin HTL-free PSC based on silver nanoparticles (NPs) at the perovskite layer/back electrode interface is proposed to increase the light trapping. The thickness of the perovskite layer is only 150 nm. The NPs radius is designed based on Mie theory to lead the highest scattering. By employing a numerical analysis, the effect of the periodicity of NPs on the performance of the PSCs is studied to obtain improved structure. The improved structure showed an absorption enhancement of 48% compared with the device without NPs within 300 nm-1400 nm wavelength. Light scattering and near field enhancement supplied by the Ag NPs are responsible for the broadband absorption increase. Photovoltaic characterizations of the improved proposed solar cell are obtained with coupled optical- electrical numerical analysis. The results showed 25.09 mA/cm(2) and 14.96%, respectively, for short-circuit current density and efficiency that the efficiency improved by 56% compared to PSCs without NPs. It is believed that this investigation can provide approaches for the design and production of simple, efficient, and economical PSCs.
查看更多>>摘要：Bound states in the continuum (BICs) have received increasing attention due to their ultra-sharp resonance in the field of ultra-sensitive sensing and trace amount detection in the terahertz (THz) regime. In this paper, we propose a new asymmetric all-dielectric THz metamaterial and show that quasi-BICs result in four ultrahigh quality (Q) factor resonances observed in the transmission spectrum. The Q factors of resonances can be achieved up to 252248. Electromagnetic field distribution and multipolar decomposition of scattering power are performed to clarify the physical mechanism of quasi-BICs resonances. In addition, the spectra response to the analytes exhibited the ability of the proposed device as an ultra-sensitive sensor, and the maximum sensitivity is 482 GHz/RIU. We further find that the sensitivity of the metamaterial is proportional to the negative quadratic of the gap between structures and explain it by the area of the field enhancement in the metamaterial. Our work paves a novel way to design ultra-high Q resonance metamaterials and ultra-sensitive sensors at THz frequencies.
查看更多>>摘要：In the LEO optical satellite network (OSN), each satellite has more than a dozen potential links, but the number of onboard terminals is limited. The beam divergence angle of optical satellite communication is extremely small, so only one bidirectional communication link can be established between a pair of communication terminals, therefore how to use limited onboard communication terminals to establish inter-satellite links (ISLs) for each satellite to achieve high-efficiency communication is an urgent problem to be solved. However, previous studies on link assignment schemes cannot take into account the terminal utilization ratio and the small end-to-end delay of the network. To solve the above-mentioned link assignment problem, this paper proposes the link assignment scheme based on vertex deleting using adjacency matrix (VDAM-LAS) for the first time. This scheme can ensure that any number of communication terminals on each satellite can be used to establish ISLs and the smaller network delay and ISLs hops can be obtained. In addition, it solves the link assignment problem of the OSN with the limit of the maximum allowable link hops of a single satellite, which is a problem that cannot be optimized using the previous LASs. The simulation results show that when assigning incessant ISLs, compared with the Manhattan Street Network (MSN)-LAS, greedy-LAS and perfect match model (PMM)-LAS, the average hops are reduced by 8.87%, 3.13%, 0.49%, respectively, and the average propagation delay is reduced by 17.24%, 2.86%, 0.8%, respectively. When assigning intermittent ISLs, the average hops are reduced by 10.45% and 6.89%, respectively, compared with the greedy-LAS and PMM-LAS.
NSTL
Elsevier