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Register a new userDegenerate Perturbation Theory Describing the Mixing of Orbital Angular Momentum Modes in Fabry-Perot Cavity Resonators
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We present an analytic perturbation theory which extends the paraxial approximation for a common cylindrically symmetric stable optical resonator and incorporates the differential, polarization-dependent reflectivity of a Bragg mirror. The degeneracy of Laguerre-Gauss modes with distinct orbital angular momentum (OAM) and polarization, but identical transverse order N, will become observably lifted at sufficiently small size and high finesse. The resulting paraxial eigenmodes possess two distinct OAM components, the fractional composition subtly depending on mirror structure.
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The dynamical response of an optical Fabry-Perot cavity is investigated experimentally. We observe oscillations in the transmitted and reflected light intensity if the frequency of the incoupled light field is rapidly changed. In addition, the decay of a cavity-stored light field is accelerated if the phase and intensity of the incoupled light are switched in an appropriate way. The theoretical model by M. J. Lawrence em et al, JOSA B 16, 523 (1999) agrees with our observations.
We demonstrate the spin to orbital angular momentum transfer in the nonlinear mixing of structured light beams. A vector vortex is coupled to a circularly polarized Gaussian beam in noncollinear second harmonic generation under type-II phase match. The second harmonic beam inherits the Hermite-Gaussian components of the vector vortex, however, the relative phase between them is determined by the polarization state of the Gaussian beam. This effect creates an interesting crosstalk between spin and orbital degrees of freedom, allowing the angular momentum transfer between them. Our experimental results match the theoretical predictions for the nonlinear optical response.
Wireless communications, radio astronomy and other radio science applications are predominantly implemented with techniques built on top of the electromagnetic linear momentum (Poynting vector) physical layer. As a supplement and/or alternative to this conventional approach, techniques rooted in the electromagnetic angular momentum physical layer have been advocated, and promising results from proof-of-concept radio communication experiments using angular momentum were recently published. This sparingly exploited physical observable describes the rotational (spinning and orbiting) physical properties of the electromagnetic fields and the rotational dynamics of the pertinent charge and current densities. In order to facilitate the exploitation of angular momentum techniques in real-world implementations, we present a systematic, comprehensive theoretical review of the fundamental physical properties of electromagnetic angular momentum observable. Starting from an overview that puts it into its physical context among the other Poincare invariants of the electromagnetic field, we describe the multi-mode quantized character and other physical properties that sets electromagnetic angular momentum apart from the electromagnetic linear momentum. These properties allow, among other things, a more flexible and efficient utilization of the radio frequency spectrum. Implementation aspects are discussed and illustrated by examples based on analytic and numerical solutions.
While nanoscale color generations have been studied for years, high performance transmission structural colors, simultaneously equipped with large gamut, high resolution, low loss and optical multiplexing abilities, still remain as a hanging issue. Here, beneficial from metasurfaces, we demonstrate a silicon metasurface embedded Fabry-Perot cavity (meta-FP cavity), with polydimethylsiloxanes (PDMS) surrounding media and silver film mirrors. By changing the planar geometries of the embedded nanopillars, the meta-FP cavity provides transmission colors with ultra large gamut of 194% sRGB and ultrahigh resolution of 141111 DPI, along with considerably average transmittance of 43% and more than 300% enhanced angular tolerance. Such high density allows two-dimensional color mixing at diffraction limit scale. The color gamut and the resolution can be flexibly tuned and improved by modifying the silver film thickness and the lattice period. The polarization manipulation ability of the metasurface also enables arbitrary color arrangement between cyan and red for two orthogonal linear polarization states, at deep subwavelength scale. Our proposed cavities can be used in filters, printings, optical storages and many other applications in need of high quality and density colors.
We demonstrate the fabrication of ultra-low-loss, all-fiber Fabry-Perot cavities containing a nanofiber section, optimized for cavity quantum electrodynamics. By continuously monitoring the finesse and fiber radius during fabrication of a nanofiber between two fiber Bragg gratings, we are able to precisely evaluate taper transmission as a function of radius. The resulting cavities have an internal round-trip loss of only 0.31% at a nanofiber waist radius of 207 nm, with a total finesse of 1380, and a maximum expected internal cooperativity of $sim$ 1050 for a cesium atom on the nanofiber surface. Our ability to fabricate such high-finesse nanofiber cavities may open the door for the realization of high-fidelity scalable quantum networks.
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