Modeling light-sound interaction in nanoscale cavities and waveguides

Abstract

Abstract:The interaction of light and sound waves at the micro and nanoscale has attracted considerable interest in recent years. The main reason is that this interaction is responsible for a wide variety of intriguing physical phenomena, ranging from the laser-induced cooling of a micromechanical resonator down to its ground state to the management of the speed of guided light pulses by exciting sound waves. A common feature of all these phenomena is the feasibility to tightly confine photons and phonons of similar wavelengths in a very small volume. Amongst the different structures that enable such confinement, optomechanical or phoxonic crystals, which are periodic structures displaying forbidden frequency band gaps for light and sound waves, have revealed themselves as the most appropriate candidates to host nanoscale structures where the light-sound interaction can be boosted. In this review, we describe the theoretical tools that allow the modeling of the interaction between photons and acoustic phonons in nanoscale structures, namely cavities and waveguides, with special emphasis in phoxonic crystal structures. First, we start by summarizing the different optomechanical or phoxonic crystal structures proposed so far and discuss their main advantages and limitations. Then, we describe the different mechanisms that make light interact with sound, and show how to treat them from a theoretical point of view. We then illustrate the different photon-phonon interaction processes with numerical simulations in realistic phoxonic cavities and waveguides. Finally, we introduce some possible applications which can take enormous benefit from the enhanced interaction between light and sound at the nanoscale.

Finite element analysis of surface modes in phononic crystal waveguides

“…The centre frequency of the lowest bandgap in the PnC induced by Bragg scattering is at about u/2a, u is the velocity and a is the lattice constant, the corresponding wavelength is twice of the lattice constant, so this bandgap is not induced by Bragg scattering. 21 Based on the analysis in Ref. 31, we attribute this bandgap to the interaction of normal acoustic band branches and a flat band produced by the local resonance of the phononic structure, which means that the resonant modes of the pillars interact with surface modes of the substrate to open bandgaps.…”

“…Especially, high frequency SAWs have found applications in material characterization, photonic modulation, phononic sensor, optomechanics, and transport by phonons or other excitations in solids. 20,21 Periodic nanostructures are used to modify the properties of SAWs, perturbing the stress and velocity fields associated with SAW propagation. 22,23 The published studies show that the filling factor, the ratio of the slab thickness to the lattice period, and the height of the pillar are the key parameters for the existence of complete bandgaps.…”

Optomechanic interactions in phoxonic cavities

“…A review of the modeling of light-sound interaction in nanoscale cavities and waveguides is given in Ref. 23.…”

Optical wave evolution due to interaction with elastic wave in a phoxonic crystal slab waveguide

“…Using that interaction one can measure position beyond the standard quantum limit [23,24]. Different mechanisms may be responsible for interaction of electromagnetic and elastic waves, among them are electrostriction, magnetostriction, radiation pressure, piezoelectricity, photoelasticity, and interface displacement [25]. The first three are mechanisms through which optical waves affect elastic waves.…”