Laser technology has been promoting various microscopy methods and thus making great progresses in life science. Further than contribution to ``seeing is believing'', lasers have also demonstrated their capacity of manipulating cells and even molecular signaling. Specifically, with advances of lasers and combination with other techniques, recent reports show that cell calcium ion, a universal intra- and inter-cellular messenger, can be modulated by lasers at different levels of biological organization from organelle to tissue. It is very encouraging that laser irradiation can activate or control plenty of corresponding cell processes and functions by regulating cell calcium signaling pathways, with promising potential in both scientific research and clinical application. In this paper, optical techniques for regulation of cell calcium signaling are specifically reviewed. Most methods need exogenouschemicals or genetic materials to convert incident photon into stimulation that cells can response with specific molecular dynamics. The only all-optical approach is achieved by nonlinear excitation with femtosecond laser, despite lack of specificity and controllability, providing possibility of a totally noninvasive method without any biochemical materials and thus further potential clinical application in human beings. The developments and techniques of those methods are introduced and explained, with analysis on their properties and current challenges. Potential applications and prospective development are also discussed. Researchers on biophotonics and related biological fields can benefit from this review. It also provides a systematic reference to doctors and researchers who are working on practical application of those methods.
Canonical solutions to frequency domain Maxwell's equations in the spherical coordinate system have found extensive use in the scientific literature. What is conspicuous by its absence is lack of such expressions for transient Maxwell systems. The existence of such expressions or approximations provide the means to glean interesting physics as well as validate existing numerical fullwave solvers. However, developing such expressions is beset with challenges; direct inverse Fourier transforms of frequency domain expressions are unstable. Successful approaches that ameliorate this instability are more recent endeavor. In this paper, we generalize our earlier contribution to this effort by exploiting a novel representation of the retarded potential to derive expressions for scattering from a dielectric sphere. Several results are provided that demonstrate the stability and accuracy of the method.
Realizations of celestial objects in the laboratory have been a tantalizing subject for human beings over centuries. In this paper, we review some of the interesting cases of realizations of black holes in the laboratory. We first review the recent progress in observed black holes realized through the isotropic coordinate transformation method, then discuss the realization of optical attractors. Finally, the Rindler space-time, as a one-dimensional black hole, by using the hyperbolic metamaterials, is discussed.
It is known that slabs of wire media - dense arrays of thin conducting wires - can transport electromagnetic energy of evanescent plane waves over the slab thickness. This phenomenon was successfully used in superlenses and endoscopes. However, in the known configurations the effective energy transfer takes place only at the Fabry-Perot (thickness) resonances of the slab, making broadband power transfer impossible. In this paper we experimentally demonstrate that power transfer by a wire medium slab can be very broadband, whereas the Fabry-Perot resonances are damped, provided that the wires of the wire medium slab extend into the power-emitting body. As a testbed system we have used two rectangular waveguides and demonstrated that a properly designed and positioned wire medium slab transfers modes of any polarization from the input to the output waveguides. This study is relevant to emerging applications where broadband transport of reactive-field energy is required, especially in enhancing and controlling radiative heat flows in thermophotovoltaic systems.
An efficient quantum mechanical approach is formulated to model electron-photon interactions in nanoscale devices. Based on nonequilibrium Green's function formalism, electron-photon interactions and open boundaries in the nanoscale systems are taken into account in terms of self-energies. By separating different components in the electron-photon interactions, optical absorption and emission processes in the devices can be analyzed, and the method allows studies of different optoelectronic devices. In conjunction with density-functional tight-binding method, photo-induced current and other optical properties of nanoscale devices can be simulated without relying on empirical parameters. To demonstrate our approach, numerical studies of gallium nitride nanowire solar cells of realistic sizes are presented.
This work investigates an adaptive, parallel and scalable integral equation solver for very large-scale electromagnetic modeling and simulation. A complicated surface model is decomposed into a collection of components, all of which are discretized independently and concurrently using a discontinuous Galerkin boundary element method. An additive Schwarz domain decomposition method is proposed next for the efficient and robust solution of linear systems resulting from discontinuous Galerkin discretizations. The work leads to a rapidly-convergent integral equation solver that is scalable for large multi-scale objects. Furthermore, it serves as a basis for parallel and scalable computational algorithms to reduce the time complexity via advanced distributed computing systems. Numerical experiments are performed on large computer clusters to characterize the performance of the proposed method. Finally, the capability and benefits of the resulting algorithms are exploited and illustrated through different types of real-world applications on high performance computing systems.
Efficient and accurate computer simulation of wave phenomena plays an important role in invention, development, cost reduction and optimization of many systems ranging from ultra-high-speed electronics to delicate nanoscale optical devices and systems. Understanding the physics of many modern technological applications such as optical nanomaterials calls for the solution of very complex computer models involving hundreds of millions to billions of unknowns. Integral equation (IE) methods are increasingly becoming the method of choice when comes to numerical modeling of wave phenomena for various reasons specifically since the introduction of FMM and MLFMA acceleration that tremendously reduce the computational costs associate with naive implementation of IE methods. In this work, a new acceleration technique specifically designed for the modeling of large, inhomogeneous, finite array problems it introduced. Specifically we use the new method for modelling and design of some metamaterial structures. At last, the presented method is used to study the some of the undesired random effects that occur in metamaterial array fabrication.
In this paper we analyze the 3D modes of a linear homogeneous magnetoelectroelastic (MEE) material reduced to magnetoelectric (ME) constitutive form. This allows convenient examination of the predominately electromagnetic behavior in a mechanically coupled MEE material system. We find that the behavior of the electromagnetic modes are strongly in fluenced by the mechanical coupling present in the MEE material system. A number of papers refer to the cross-coupling of laminated piezoelectric and piezomagnetic materials as magnetoelectric materials. We discuss here that the composite materials are MEE systems and that the constitutive relations need to reflect the mechanical coupling also. Further, we find that the mechanical coupling has a significant impact on the electromagnetic propagation modes of the composite material. Through examples of homogenized MEE materials we show possibilities for remarkable electromagnetic material characteristics which are not conventionally obtainable in single phase materials.
While considerable progress has been made in the realm of speed-enhanced electromagnetic (EM) solvers, these fast solvers generally achieve their results through methods that introduce additional error components by way of geometric type approximations, sparse-matrix type approximations, multilevel type decomposition of interactions, and assumptions regarding the stochastic nature of EM problems. This work introduces the O(N logN) Uni ed-FFT grid totalizing (UFFT-GT) method, a derivative of method of moments (MoM), which achieves fast analysis with minimal to zero reduction in accuracy relative to direct MoM solution. The method uniquely combines FFT-enhanced Matrix Fill Operations (MFO) that are calculated to machine precision with FFT-enhanced Matrix Solve Operations (MSO) that are also calculated to machine precision, for an expedient solution that does not compromise accuracy.
The reflectivity measurement of materials is an innovative application of a reverberation chamber (RC). In this paper we show an analysis of the performance of the reflectivity measurement in an RC in terms of uncertainty of measurement and relevant noise level. The model for reflectivity measurement, which is already present in literature, is based on the absorption cross section (ACS) measurements. If the ACS measurements are averaged with respect to the configurations of the measurement system, then the relevant uncertainty depends only on the number of independent samples. Here, the performance of the reflectivity measurements is shown in cases where it depends only on the number of independent samples acquired in an RC. Simulations and measurements confirm the validity of the expected results.
A new circularly-polarized metasurfaced dipole antenna (MSDA) with wide axial-ratio(AR) beamwidth and radar cross section (RCS) reduction properties is proposed and studied in this paper. This antenna is a quite simple half-wavelength linear dipole right above a metasurface which consists of 9 double-head arrow-shaped unit cells arranged in a 3×3 layout. By cautiously choosing the geometrical parameters of the metasurface and tuning the distance between the dipole and the metasurface, the whole structure turns out to be a circularly-polarized antenna with RCS reduction feature. Simulation results show that the MSDA in circular polarization achieves an operating bandwidth of 410 MHz and a wide AR beamwidth of 123˚ and 90˚ in φ = 0˚ and φ = 90˚ planes respectively, together with a maximum RCS reduction of 10.4 dB in the whole operating band.
Nosecone radomes of hypersonic flight vehicles show degradation of electromagnetic (EM) performance characteristics due to variations in the dielectric parameters (dielectric constant and electric loss tangent) of the radome wall resulting from heating due to extreme aerodynamic drag. It is indicated that the EM performance predictions based on conventional monolithic half-wave wall based on average dielectric parameters corresponding to temperature ranges in hypersonic conditions may not be accurate. This necessitates the radome wall under hypersonic conditions to be modeled as an inhomogeneous dielectric structure for accurate EM performance predictions. In the present work, the hypersonic radome is considered as an inhomogeneous dielectric radome such that the cross-section of the radome wall in each EM window region is considered as an inhomogeneous planar layer (IPL) model with stacked layers of varying dielectric parameters. The material considered is RBSN Ceralloy 147-010F (an alloy of silicon nitride), which has excellent thermal shock resistance, dielectric and mechanical properties required for hypersonic radome applications. The EM modeling of a section of the radome wall in hypersonic conditions (i.e. IPL structure) is based on Equivalent Transmission Line Method. A comparative study of basic EM performance parameters of the radome wall (power transmission, power reflection, and insertion phase delay) for both the IPL model and conventional monolithic half-wave model are carried out over a range of incidence angles corresponding to the antenna scan ranges in each EM window region of the radome. Further the study is extended to compute the EM performance parameters of an actual tangent ogive nosecone radome (made of RBSN Ceralloy 147-010F) enclosing an X-band slotted waveguide planar array antenna, in a hypersonic environment. The antenna-radome interaction studies are based on 3-D Ray tracing in conjunction with Aperture Integration Method. It is observed that the EM performance analysis based on conventional monolithic radome wall design cannot accurately predict the radome performance parameters in actual operating conditions during hypersonic flight operations. The current work establishes the efficacy of Inhomogeneous Dielectric Radome model for better EM performance predictions of streamlined airborne radomes in hypersonic environments.
We present a critical account of intense pulsed-laser field induced refractive index changes caused by flow, crystalline axis reorientation and distortion and other high order photonic processes in transparent liquid crystals. In particular, the optical nonlinearity associated with Maxwell Stress induced flow-reorientation in nematic liquid crystals is explicitly calculated, and their possibility for all-optical switching application is experimentally demonstrated. Similar flows processes have also been observed in Blue-Phase liquid crystals with nanosecond and picosecond pulsed-lasers.
The plasmonic behavior of nanostructured materials has ignited intense research for the fundamental physics of plasmonic structures and their cutting edge applications concerning the fields of nanoscience and biosensing. The optical response of plasmonic metals is generally well-described by classical Maxwell's Equations (ME). Thus, the understanding of plasmons and the design of plasmonic nanostructures can therefore directly benefit from lastest advances achieved in classic research areas such as computational electromagnetics. In this context, this paper is devoted to review the most recent advances in nanoplasmonic modeling, related with the latest breakthroughs in surface integral equation (SIE) formulations derived from ME. These works have extended the scope of application of Maxwell's Equations, from microwave/milimeter waves to infrared and optical frequency bands, in the emerging fields of nanoscience and medical biosensing.
Two basic classes of electromagnetic medium, recently defined as P and Q medium, are generalized to define the class of PQ media. Plane wave propagation in the general PQ medium is studied and the quartic dispersion equation is derived in analytic form applying four-dimensional dyadic formalism. The result is verified by considering various special cases of PQ media for which the dispersion equation is either decomposed to two quadratic equations or is identically satisfied (media with no dispersion equation). As a numerical example, the dispersion surface of a PQ medium with non-decomposable dispersion equation is considered.
Novel microwave imaging systems require flexible forward solvers capable of incorporating arbitrary boundary conditions and inhomogeneous background constitutive parameters. In this work we focus on the implementation of a time-harmonic Discontinuous Galerkin Method (DGM) forward solver with a number of features that aim to benefit tomographic microwave imaging algorithms: locally varying high-order polynomial field expansions, locally varying high-order representations of the complex constitutive parameters, and exact radiating boundary conditions. The DGM formulated directly from Maxwell's curl equations facilitates including both electric and magnetic contrast functions, the latter being important when considering quantitative imaging with magnetic contrast agents. To improve forward solver performance we formulate the DGM for time-harmonic electric and magnetic vector wave equations driven by both electric and magnetic sources. Sufficient implementation details are provided to permit existing DGM codes based on nodal expansions of Maxwell's curl equations to be converted to the wave equation formulations. Results are shown to validate the DGM forward solver framework for transverse magnetic problems that might typically be found in tomographic imaging systems, illustrating how high-order expansions of the constitutive parameters can be used to improve forward solver performance.
Submit
