The modulation of coupling in the relaxation behavior of light transmitted through binary ferrofluids

With an external magnetic field, a relaxation process is observed when the light transmit through binary ferrofluids composed of ferrimagnetic CoFe₂O₄ and paramagnetic p-NiFe₂O₄ nanoparticles similar to ferrofluids consisting only of CoFe₂O₄. Since only the ferrimagnetic nanoparticles are able to form field-induced chainlike structures for such binary ferrofluids by magnetic interaction between the particles, so the relaxation behavior of the transmitted light is caused mainly by the ferrimagnetic system. In the binary ferrofluids, the paramagnetic nanoparticles, regarded as magnetically polarized gas molecules, are restrained to occupy the space between the ferrimagnetic chains and distribute following the CoFe₂O₄ particle chains covering and diverging, producing a modulation effect on the relaxation behavior of the transmitted light. The modulation effect can be characterized by range and time parameters that describe the relationship of the relaxation behavior of the transmitted light to the properties of the binary ferrofluids and single CoFe₂O₄ ferrofluids.     

Relaxation behavior measuring of transmitted light through ferrofluids film

In this paper, relaxation behavior of transmitted light through thin ferrofluid film under an applied magnetic field is measured. The results show that the intensity of transmitted light through a ferrofluid film increases quickly as soon as an external magnetic field is applied then weakens with time. If uniformity of the field is poor, the transmission of light continuously decreases in a measured duration. Otherwise, the transmission of light will tend increasingly towards a stable value after it decreases to a minimum value while the gradient of the field is low. The relaxation time would increase to an order of some hundreds seconds magnitude and is dependent on the strength of magnetic field and viscosity of the ferrofluids. The field-induced relaxation behaviors of transmitted light through ferrofluids correspond to anisotropic microstructure of the ferrofluids under applied magnetic field. PACS 75.50.Mm; 78.20.Ls     

Extinction of polarized light in ferrofluids with different magnetic particle concentrations

The magnetic field intensity and nanoparticle concentration dependence of the polarized light extinction in a ferrofluid made of magnetite particles stabilized with technical grade oleic acid dispersed in transformer oil was experimentally investigated. The magnetically induced optical anisotropy, i.e. the dichroism divided by concentration, was found to decrease with increasing sample concentration from 2% to 8%. The magnetically induced change in the optical extinction of light polarized at 54.74° with respect to the magnetic field direction was found to be positive for the less concentrated sample (2%) and negative for the samples with 4% and 8% magnetic nanoparticle concentrations, the more negative the higher the concentration and field intensity. Based on the theoretically proven fact [11] that the particle orientation mechanism has no effect on the extinction of light polarized at 54.74° with respect to the field direction, we analyzed the experimental findings in the frames of the agglomeration and long-range pair correlations theories for the magnetically induced optical anisotropy in ferrofluids. We developed a theoretical model in the approximation of single scattering for the optical extinction coefficient of a ferrofluid with magnetically induced particle agglomeration. The model predicts the existence of a polarization independent component of the optical extinction coefficient that is experimentally measurable at 54.74° polarization angle. The change in the optical extinction of light polarized at 54.74° is positive if only the formation of straight n-particle chains is considered and may become negative in the hypothesis that the longer chains degenerate to more isotropic structures (polymer-like coils, globules or bundles of chains). The model for the influence on the light absorption of the long-range pair correlations, published elsewhere, predicts that the change in the optical extinction of light polarized at 54.74° is always negative, the more negative the higher the magnetic field intensity and particle concentration.     

Phase relations in the modulation of light through the linear electro-optical effect

General expressions for the phases of the two light waves passing through a crystal plate in the normal direction are developed for arbitrary directions of the optic axis of a monoaxial crystal and of the electric vector of the modulating, linearly polarized superhigh frequency wave. The expressions obtained permit one to describe in general form the amplitude, polarization, and phase modulations of light by electrooptical modulators.     

通过磁光效应研究磁性液体在外场下的颗粒成链现象

在对磁性液体的磁光效应的理论分析与实验测量的基础上讨论了其在磁场下的各向异性现象.首先,通过电磁理论对成链的各向异性介质模型的介电张量形式进行了一般性的分析,然后,基于磁性液体的微观理论模型讨论了磁性液体在外加磁场下出现凝聚成链的行为.基于上面的结果,我们将实验可观测量——两种传输模式的折射率差和不同颗粒数的链(长度不同的链)的比例以及磁场强度建立联系.最后,在实验上探测了磁性液体薄膜的透射光偏振状态变化随外磁场的变化,并对测得的数据进行计算机拟合分析,验证了不同长度的链的数目之间的比例关系.     

Delay in light transmission through small apertures

We demonstrate a technique for measuring pulse propagation time delays with 0.5-fs resolution by use of a widely available 100-fs pulsed laser. Using this technique, we measured the time delay of a light pulse transiting through subwavelength apertures placed on a 0.3-mum metallic film. We measured a 7-fs total transit time, corresponding to an effective group velocity of c/7 . The experimental result yielded additional evidence that light interacts resonantly with oscillators formed by the surface modes near the small apertures.     

Ultrahigh light transmission through a C-shaped nanoaperture

Optical resolution beyond the diffraction limit can be achieved by use of a metallic nanoaperture in a near-field optical system. Conventional nanoapertures have very low power throughput. Using a numerical finite-difference time domain method, we discovered a unique C-shaped aperture that provides approximately 3 orders of magnitude more power throughput than a conventional square aperture with a similar near-field spot size of approximately 0.1 lambda. Microwave experiments at 6 GHz quantitatively confirmed the simulated transmission enhancement. The high transmission of the C-aperture--or one of the related shapes--is linked to both a propagation mode in the aperture and local surface plasmons.     

The effect of workmanship on the transmission of airborne sound through light framed walls

A study of the airborne sound transmission in a multi-tenanted building has shown that elements of the building which are nominally identical do not have the same acoustic performance. It was seen that some of this variation in performance could be attributed to visually-observable differences in the constructions. Some of the variation could not be explained however, and it was concluded that this variation was due to workmanship. The level of this variation was seen to be approximately 1 dB for a light steel framed construction. This variation is considerably less than that measured previously for a monolithic construction.     

Two resonances effect for light transmission assisted with surface plasmon through perforated metal film

When light is incident on a nonplanar metal surface, an oscillating dipole is excited at the entrance openings. We show that the enhanced transmission assisted with surface plasmon (SP) through a perforated metal film results from two different SP resonances effects: (i) zero-order Fabry-Perot resonance effect where each air hole can be considered as a section of metallic waveguide, forming a low-quality-factor resonator, and many dipoles are arranged inside the nanoholes region; and (ii) structure-factor-induced charges self-tunnelling effect due to the well-recognized surface structure periodicity, where the positive or negative charges can respectively tunnel into the right surface through the metal walls. Furthermore, when light transmits through the double-layer perforated metal films, the different transport behaviors are also clearly shown, which convinces the existence of dual SP resonances effect.     

Tunneling mechanism of light transmission through metallic films

A mechanism of light transmission through metallic films is proposed, assisted by tunneling between resonating buried dielectric inclusions. This is illustrated by arrays of Si spheres embedded in Ag. Strong transmission peaks are observed near the Mie resonances of the spheres. The interaction among various planes of spheres and interference effects between these resonances and the surface plasmons of Ag lead to mixing and splitting of the resonances. Transmission is proved to be limited only by absorption. For small spheres, the effective dielectric constant of the resulting material can be tuned to values close to unity, and a method is proposed to turn the resulting materials invisible.     

High light transmission through thin absorptive corrugated films

The enhancement of light transmittance through periodically relief thin absorptive film at surface plasmon polariton excitation conditions, as a function of relief interrelation, was considered theoretically. Our calculation of transmittance-reflectance through periodically relief thin absorptive film was performed in the framework of differential formalism. There are two basic relief interrelation forms, namely, correlated and anticorrelated ones. The obtained spectral and angular dependencies demonstrate an essential increase of surface plasmon polariton peaks in the case of anticorrelated corrugation of film in comparison with the correlated ones.     

Universal optimal transmission of light through disordered materials

We experimentally demonstrate increased diffuse transmission of light through strongly scattering materials. Wave front shaping is used to selectively couple light to the open transport eigenchannels, specific solutions of Maxwell's equations which the sample transmits fully, resulting in an increase of up to 44% in the total angle-integrated transmission compared to the case where plane waves are incident. The results for each of several hundreds of experimental runs are in excellent quantitative agreement with random matrix theory. From our measurements we conclude that with perfectly shaped wave fronts the transmission of a disordered sample tends to a universal value of 2/3, regardless of the thickness.     

Enhanced light transmission through a single subwavelength aperture

The optical transmission through a subwavelength aperture in a metal film is strongly enhanced when the incident light is resonant with surface plasmons at the corrugated metal surface surrounding the aperture. Conversely, the aperture acts as a novel probe of the surface plasmons, yielding useful insights for optimizing the transmission enhancement. For the optimal corrugation geometry, a set of concentric circular grooves, three times more light is transmitted through the central subwavelength aperture than directly impinges upon it. This effect is useful in the fabrication of near-field optical devices with extremely high optical throughput.     

Constraining the parameters of binary systems through time-dependent light deflection

A theory is derived relating the configuration of the cores of active galaxies, specifically candidates for presumed super-massive black hole binaries (SMBHBs), to time-dependent changes in images of those galaxies. Three deflection quantities, resulting from the monopole term, mass quadrupole term, and spin dipole term of the core, are examined. The resulting observational technique is applied to the galaxy 3C66B. This technique is found to under idealized circumstances surpass the technique proposed by Jenet et al. in accuracy for constraining the mass of SMBHB candidates, but is exceeded in accuracy and precision by Jenet’s technique under currently understood likely conditions. The technique can also under favorable circumstances produce results measurable by currently available astronomical interferometry such as very-long-baseline interferometry (VLBI).     

Compact transmission system using single-sideband modulation of light for quantum cryptography

We report a new transmission that can be used for quantum key distribution. The system uses single-sideband-modulated light in an implementation of the BB84 quantum cryptography protocol. The system is formed by two integrated unbalanced Mach-Zehnder interferometers and is based on interference between phase-modulated sidebands in the spectral domain. Experiments show that high interference visibility can be obtained.     

A nonlinear stability analysis of a double-diffusive magnetized ferrofluid with magnetic field-dependent viscosity

A rigorous nonlinear stability result is derived by introducing a suitable generalized energy functional for a magnetized ferrofluid layer heated and soluted from below with magnetic field-dependent (MFD) viscosity, for stress-free boundaries. The mathematical emphasis is on how to control the nonlinear terms caused by magnetic body and inertia forces. For ferrofluids, we find that there is possibility of existence of subcritical instabilities, however, it is noted that in case of non-ferrofluid, global nonlinear stability Rayleigh number is exactly the same as that for linear instability. For lower values of magnetic parameters, this coincidence is immediately lost. The effects of magnetic parameter, M₃, solute gradient, S₁ and MFD viscosity parameter, δ, on the subcritical instability region have also been analyzed.     

Use of magnetostriction effect to stabilize laser frequency

The use of magnetostriction to compensate for the thermal changes of the lasercavity length in automatic frequency control systems is considered. Magnetostriction ensures a wide dynamic range of cavity-length compensation, and a transfer coefficient that is 10²–10³ times larger.Translated from Lazernye Sistemy, pp. 109–111, 1982.     

Optical transmission properties of light propagation through Fibonacci-class ring-resonators

An interesting topology with easy integration capability (from mask designing aspect) for optical filters using Fibonacci-class (FC(J,n)) ring-resonators is introduced. For some special cases, analytical transfer function (Transmission Coefficient H_m⁽ⁿ⁾) is obtained and corresponding simulated result is illustrated. In this work, optical multi-band filter design and analysis using Fibonacci-class ring resonators is considered. With suitable selection of system parameters and FC(J,n), we report multi-band characteristic for this structure. Also, dominant factors effects on multi-band operation are shown. We show that the coupling coefficients, effectively affects (e.g. generation or annihilation of additional band) the multi-band properties obtained in proposed structure. Also, the bandwidth and position of additional band can be controlled using Fibonacci-class basic elements (A, B) parameters such as rings diameters. Also, proposed system is easier than general multistage rings coupled to main waveguide from implementation point of view.     

Finite-difference time-domain studies of light transmission through nanohole structures

We present theoretical studies on the transmission of light through subwavelength, circular apertures surrounded by circular groove structures. Finite-difference time-domain equations in cylindrical coordinates are provided for both dispersive materials and electrical conductors. The nanohole systems are composed of a circular hole in a slab, that is encircled by sinusoidal grooves defined by a period and depth. Light transmission is found to be extremely sensitive to the hole size, groove period, and groove depth. We determine a set of groove parameters that optimize transmission. Enhancements in transmission by approximately a factor of four can be achieved for silver in the visible when compared to the light incident upon the hole. These results may find utility in the design of nanoscale light manipulating devices. PACS 73.20.Mf; 78.20.Ci; 78.68.+m; 64.47.-n; 03.50.De     

Mach–Zehnder interferometer by utilizing phase modulation of transmitted light through magnetic fluid films possessing tunable refractive index

Due to its diverse applications in photonics, bio-sensors, mechanics, etc., Mach–Zehnder interferometer becomes one of important devices. Hence, lots of efforts have been paid to develop advanced Mach–Zehnder interferometers. In this work, we explore new-model Mach–Zehnder interferometer, in which one of arm is consisted of magnetic fluid films. By utilizing the tunable refractive index of magnetic fluid films under external magnetic fields, the traveling phase of a propagating light through the magnetic fluid film is changed. This could lead to a variation in the interfered intensity of the Mach–Zehnder interferometer when an external magnetic field is applied. The modulation in the interfered intensity by the external magnetic field is demonstrated experimentally, and the relevant physical origin is also discussed.