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Register a new userReflection and Refraction of the Laser Light Pulse at the Vacuum-Medium Interface
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By generalizing the well known results for reflection and refraction of plane waves at the vacuum-medium interface to Gaussian light beams, we obtain analytic formulas for reflection and refraction of the TM and TE laser light pulses. This enables us to give a possible explanation why no reflection was observed in light pulse photographs in some vicinity of the air-resin interface, given in L. Gao, J. Liang, C. Li, and L. V. Wang, Nature 516 (2014) 74-77. We suggest how to modify the experimental setup so as to observe the reflected pulse.
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We construct a binary synthetic photonic lattice theoretically with an effective magnetic field by projecting two fiber loops light intensity and adjusting the phase distribution precisely. By tuning the phase modulator, wave vector, and propagation constant of an effective waveguide, the interfaces transmittance could be manipulated. Further light dynamics show that the light pulse can achieve total reflection without diffraction and exchanges the light energy in two optical fiber loops completely when phase distribution and wave vector meet certain conditions. Our study may provide a new way to realize optical switches in optical interconnection and optical communication.
In this talk we present and discuss a new general approach to the synthesis of metasurfaces for full control of transmitted and reflected fields. The method is based on the use of an equivalent impedance matrix which connects the tangential field components at the two sides on the metasurface. Finding the impedance matrix components, we are able to synthesize metasurfaces which perfectly realize the desired response. We will explain possible alternative physical realizations and reveal the crucial role of bianisotropic coupling to achieve full control of transmission through perfectly matched metasurfaces. This abstract summarizes our results on metasurfaces for perfect refraction into an arbitrary direction.
Artificial gauge fields enable extending the control over dynamics of uncharged particles, by engineering the potential landscape such that the particles behave as if effective external fields are acting on them. Recent years have witnessed a growing interest in artificial gauge fields that are generated either by geometry or by time-dependent modulation, as they have been the enablers for topological phenomena and synthetic dimensions in many physical settings, e.g., photonics, cold atoms and acoustic waves. Here, we formulate and experimentally demonstrate the generalized laws of refraction and reflection from an interface between two regions with different artificial gauge fields. We use the symmetries in the system to obtain the generalized Snell law for such a gauge interface, and solve for reflection and transmission. We identify total internal reflection (TIR) and complete transmission, and demonstrate the concept in experiments. Additionally, we calculate the artificial magnetic flux at the interface of two regions with different artificial gauge, and present a method to concatenate several gauge interfaces. As an example, we propose a scheme to make a gauge imaging system - a device that is able to reconstruct (image) the shape of an arbitrary wavepacket launched at a certain position to a predesigned location.
Non-uniform metasurfaces (electrically thin composite layers) can be used for shaping refracted and reflected electromagnetic waves. However, known design approaches based on the generalized refraction and reflection laws do not allow realization of perfectly performing devices: there are always some parasitic reflections into undesired directions. In this paper we introduce and discuss a general approach to the synthesis of metasurfaces for full control of transmitted and reflected plane waves and show that perfect performance can be realized. The method is based on the use of an equivalent impedance matrix model which connects the tangential field components at the two sides on the metasurface. With this approach we are able to understand what physical properties of the metasurface are needed in order to perfectly realize the desired response. Furthermore, we determine the required polarizabilities of the metasurface unit cells and discuss suitable cell structures. It appears that only spatially dispersive metasurfaces allow realization of perfect refraction and reflection of incident plane waves into arbitrary directions. In particular, ideal refraction is possible only if the metasurface is bianisotropic (weak spatial dispersion), and ideal reflection without polarization transformation requires spatial dispersion with a specific, strongly non-local response to the fields.
A physical process of the gravitational redshift was described in an earlier paper (Wilhelm & Dwivedi 2014) that did not require any information for the emitting atom neither on the local gravitational potential U nor on the speed of light c. Although it could be shown that the correct energy shift of the emitted photon resulted from energy and momentum conservation principles and the speed of light at the emission site, it was not obvious how this speed is controlled by the gravitational potential. The aim of this paper is to describe a physical process that can accomplish this control. We determine the local speed of light c by deducing a gravitational index of refraction nG as a function of the potential U assuming a specific aether model, in which photons propagate as solitons. Even though an atom cannot locally sense the gravitational potential U (cf. Muller et al. 2010), the gravitational redshift will nevertheless be determined by U (cf. Wolf et al. 2010)- mediated by the local speed of light c.
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