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Enhanced optomechanically induced transparency with magnetic coupling
摘要： Optomechanically induced transparency is a kind of induced transparency arising from the interference of excitation pathways in optomechanical systems and can be used to realize high speed optical switches and precision measurements. Due to the intrinsic feature of optomechanical interaction, optomechanically induced transparency can only be observed under strong pump fields. However, the applications of optomechanically induced transparency in nanophotonics require low pump power and good controllability. Thus it is important to reduce the pump power and improve the controllability of optomechanically induced transparency with current experimental parameters. In this work, we propose a realizable method for the achievement of low-power optomechanically induced transparency by introducing a magnetic force coupling. We show that the magnetic coupling can obviously reduce the pump threshold value, and optomechanically induced transparency with ultralow pump threshold value and desirable controllability can be realized. In comparison to optomechanical system combining piezoelectric materials, the magnetic force-coupled optomechanical system may be a better candidate for optical information process.
关键词： optomechanically induced transparency,low-power,optical switches,precision measurements,magnetic coupling
更新于2025-09-09 09:28:46
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Assessing Transparency Control of Southern European Building Wall Structures Using Frequency-Selective Surfaces [Wireless Corner]
摘要： The concept of controlling the radio-frequency (RF) transparency of building wall structures is analyzed in this article with a focus on southern European architecture, where it is demonstrated that some materials have a significant impact on wireless propagation. As such, the integration of frequency-selective surfaces (FSSs) in some building structure arrangements might have few overall benefits. This work provides an analysis of the different elements required to modify the electromagnetic (EM) transparency of building wall layers: 1) different methods to control the frequency selectivity are identified with a special focus given to FSS, 2) some proposals on the integration of the FSS on current and new building structures are provided, 3) measurement results are presented regarding the penetration losses of multilayered wall samples, with and without the presence of FSS layers, and 4) a multilayer EM simulation tool developed in MATLAB is introduced and validated against measurement results, allowing the simulation and analysis of additional scenarios. Results are provided for a frequency range of 800 MHz up to 10 GHz.
关键词： penetration loss,building materials,electromagnetic transparency,Frequency-selective surfaces,wireless propagation
更新于2025-09-09 09:28:46
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Are optical distortions used as a cue for material properties of thick transparent objects?
摘要： Fleming, J¨akel, and Maloney (2011) asked subjects to match perceived material properties of thick, clear transparent objects in photo-realistic scenes by adjusting the refractive index. They found approximate correspondence between standard and test objects but also large systematic deviations. Nevertheless, they concluded that estimated refraction is used as an indicator for material properties of light-transmitting objects and emphasized the role of object-induced background distortions in this process. This, however, seems not plausible, because the necessary information for inferring the refractive index from distortions—for example, the object’s exact shape and thickness, its background distance, and the undistorted background—was not available in their situation. A more plausible alternative explanation is that the subjects did not match estimated refractive indices, but instead performed simple similarity matches based directly on image attributes related to background distortions or specular reflections. We tested this hypothesis in a similar matching experiment in which it was possible to predict the refractive index for a similarity match based on background distortions and for a similarity match based on specular reflections. Our subjects always chose a value between these two predictions. The specular reflection tends to be the dominant factor as soon as it becomes clearly noticeable. Our findings are compatible with the assumption that the subjects tried to find a compromise between two image-based similarity criteria. They do not seem to be consistent with the assumption that the matches are made on the basis of internal estimates of refractive indices.
关键词： optical background distortion,specular reflection,perceptual transparency
更新于2025-09-04 15:30:14
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Electrical Manipulation of Electromagnetically Induced Transparency for Slow Light Purpose Based on Metal-Graphene Hybrid Metamaterial
摘要： A terahertz metamaterial is presented and numerically investigated to achieve tunable electromagnetically induced transparency (EIT) for slow light. The unit cell consists of cut-wire pairs and U-shaped ring resonators with graphene strips placed between the metal film and the SiO2/Si substrate. Through bright-dark mode coupling, the radiative resonance induced by the U-shaped ring is suppressed, and then the typical EIT effect is realized. The transparency window and the accompanied group delay can be electrically manipulated with different Fermi energy of the graphene. By analyzing the surface distribution, the underlying tuning mechanism of this hybrid metamaterial is investigated in detail. Moreover, the transparency peak decreases slightly with the increasing strip width of the graphene layer but completely vanishes as the strip width exceeds the length of the covered U-shaped ring. The influence of the critical index of graphene quality, i.e., carrier mobility on the EIT effect, is considered. The results of this study may provide valuable guidance in designing and analyzing tunable EIT structures based on a metal-graphene hybrid structure for slow light purposes.
关键词： slow light,electromagnetically induced transparency,graphene,metamaterial
更新于2025-09-04 15:30:14
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Organosoluble and transparent cardo polyimides with high <i>T</i> <sub/>g</sub> derived from 9,9-bis(4-aminophenyl)xanthene
摘要： 9,9-Bis(4-aminophenyl)xanthene (BAPX) was prepared simply and effectively via one-pot, two-step procedure using xanthenone and aniline as main substrates. The monomer BAPX was reacted with six aromatic dianhydrides in N,N-dimethylacetamide (DMAc) to yield the corresponding polyimides (PIs) via the poly(amic acid) precursors and subsequent thermal or chemical imidization. The resulting PIs exhibited good thermal stability with glass transition temperatures of 308–348°C, initial decomposition temperatures of 470–510°C, 10% weight loss temperatures of 540–565°C, and char yields of 55–59% at 800°C in nitrogen, respectively. All polymers were amorphous and readily soluble in organic solvents such as N-methyl-2-pyrrolidone and DMAc. The PI films had tensile strengths of 71–92 MPa, tensile moduli of 1.91–2.35 GPa, and elongations at break of 5–13%. Meanwhile, these polymer films also had high optical transparency with a cutoff wavelength in the range of 367–415 nm, lower dielectric constants (3.02–3.34 at 10 MHz), and low water uptake of 0.30–0.52%.
关键词： Aromatic polyimide,9,9-bis(4-aminophenyl)xanthene,bulky pendent xanthene cardo group,thermal property,optical transparency,solubility
更新于2025-09-04 15:30:14
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Control of electromagnetically induced grating by surface plasmon and tunneling in a hybrid QD-MNP system
摘要： We investigate the electromagnetically induced grating (EIG) in a quantum dot-metal nanoparticle (QD-MNP) hybrid system. The EIG can be controlled and improved by the surface plasmon effect and the interdot tunneling effect between quantum dots. By manipulating the tunneling effect and the QD-MNP distance, not only the first-order diffraction intensity of the grating can be efficiently enhanced, but also the EIG can be switched from the absorption grating to the gain grating. Almost two times of the first-order diffraction efficiencies can be achieved in the gain gratings compared with the absorption gratings.
关键词： electromagnetically induced grating,dot-metal nanoparticle,electromagnetically induced transparency,plasmon-exciton effect,tunneling
更新于2025-09-04 15:30:14
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Rotary photon drag in a Mach-Zehnder-type Sagnac interferometer
摘要： We theoretically investigate rotary photon drag in a Mach-Zehnder type Sagnac interferometer using a four level N-type atomic medium. Splitting of a single pulse of light into two pulses is observed at high strength of the control field both in absorption and dispersion spectra. Group index, relativistic velocities and rotary photon drag are examined as a function of probe field detuning Δp. Rotation angles of ± 2, ± 3, ± 4 and ± 6 micro radians are achieved for the two beams propagating in clockwise and counter clockwise direction by varying values of the probe field detuning as 0γ, 0.5γ and 1.5γ, respectively. The results obtained show potential applications in sensing technology, optical fibre communication technology as well as in perfect lens formation.
关键词： Rotary photon drag,Light propagation,Polarization,Quantum coherence,Interferometry,Electromagnetically induced transparency
更新于2025-09-04 15:30:14
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Tunable and polarization insensitive electromagnetically induced transparency using planar metamaterial
摘要： We demonstrate a classical analogue of electromagnetically induced transparency (EIT) metamaterial that consisting of anomalous split resonance ring and cross-shaped wire with simulations and experiments. The transmission spectrum is tunable with the incident angles varies from 0° to 60° in different modes. Under normal incident wave, the metamaterial leads to polarization insensitive EIT-like effect. The distributions of surface current at peaks and dips of transmission have been analyzed. Furthermore, the group index presents maximum at the transparency peak, which verifies the slow light effect. The proposed metamaterial could provide an avenue for various applications, such as refractive index sensor and microwave switch.
关键词： polarization insensitive,tunable,electromagnetically induced transparency,metamaterial
更新于2025-09-04 15:30:14
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Tunable Fano resonances in a robust quasicylindrical microresonator photonic system
摘要： The control of Fano resonances is of critical importance to opto-electronic and all-optical switching devices, light delay and storage, high sensitivity sensors, and quantum information processors. In this paper, we controllable electromagnetically induced transparency (EIT)-like and Fano resonances can be achieved in a single quasi-cylindrical microresonator (QCMR). Robust and selective excitation of localized axial modes in a high quality QCMR is firstly demonstrated. Based on this stable platform, EIT-like lineshapes can be tuned and converted into Fano resonances by vertically moving the resonator. Moreover, by horizontally scanning the resonator, the transmission spectrum exhibits periodically changed Fano-like lineshapes. It is reported for the first time that the above two kinds of Fano resonances originated from different mechanisms can work on the same mode simultaneously. Our approach, demonstrated in this work, provides a robust photonic platform for accessing, controlling, and engineering the Fano resonances.
关键词： high sensitivity sensors,opto-electronic devices,electromagnetically induced transparency,Fano resonances,quasi-cylindrical microresonator
更新于2025-09-04 15:30:14