Phoxonic Crystal Cavities Research Articles

Topological electromagnetic and elastic states in phoxonic crystal cavity arrays

AbstractIn this paper, we investigate the topological characteristics of the phoxonic crystal (PxC) arrays. For the PxC system, the electromagnetic transverse electric mode and the elastic in‐plane mode are considered. The PxC possesses the photonic and phononic bandgaps simultaneously. Based on the bandgaps, we design the PxC cavity which can confine the electromagnetic and elastic waves. The interaction strength between the neighboring PxC cavities can be tuned by changing the distance between these cavities. The PxC cavity arrays with the topologically non‐trivial and trivial phases are obtained. We combine the PxC arrays with the topologically non‐trivial and trivial phases together. The electromagnetic and elastic topological interface states can be simultaneously observed at the interface of the PxC cavity arrays.

Acoustic diamond resonators with ultrasmall mode volumes

Quantum acoustodynamics (QAD) is a rapidly developing field of research, offering possibilities to realize and study macroscopic quantum-mechanical systems in a new range of frequencies, and implement transducers and new types of memories for hybrid quantum devices. Here we propose a novel design for a versatile diamond QAD cavity operating at GHz frequencies, exhibiting effective mode volumes of about $10^{-4}\lambda^3$. Our phononic crystal waveguide cavity implements a non-resonant analogue of the optical lightning-rod effect to localize the energy of an acoustic mode into a deeply-subwavelength volume. We demonstrate that this confinement can readily enhance the orbit-strain interaction with embedded nitrogen-vacancy (NV) centres towards the high-cooperativity regime, and enable efficient resonant cooling of the acoustic vibrations towards the ground state using a single NV. This architecture can be readily translated towards setup with multiple cavities in one- or two-dimensional phononic crystals, and the underlying non-resonant localization mechanism will pave the way to further enhance optoacoustic coupling in phoxonic crystal cavities.

Strong optomechanical coupling of light and highly confined acoustic phonons in slot dual-beam phoxonic crystal cavities

In this study, strong optomechanical (OM) coupling is proposed through the introduction of a slot in a dual-beam phoxonic crystal cavity structure. The structure can support a confined optical slot mode and localized phononic cavity modes to interact effectively through the slot surfaces. In addition to using conventional OM coupling rates for evaluating the coupling strength of photonic and phononic modes, we consider the optical forces induced by the optical slot mode to discuss the coupling between different mode pairs and the underlying mechanisms of the strong OM coupling. The optical field can induce radiation pressure and electrostrictive forces in the structure. We demonstrate that the radiation pressure dominates the coupling enhancement of photonic and phononic modes because of the slot, whereas the electrostrictive surface pressure plays a minor role and the electrostrictive body force has a negligible contribution. On the basis of the optical forces, we can then calculate the acoustic phonon spectrum through optical excitation. The spectrum indicates the appearance of strong OM coupling in the additional phononic cavity modes. The results suggest that the slot dual-beam cavity structure can be a promising choice for tailoring effective optical forces in micro- and nano-optomechanical systems for enhancing OM coupling.

REVIEW OF BANDGAP CHARACTERISTICS AND ACOUSTO-OPTICAL COUPLING IN PHOXONIC CRYSTALS

Phoxonic crystals are periodic structures which possess photonic and phononic bandgaps simultaneously. Phoxonic crystals can be applied as systematic platforms for manipulating electromagnetic and elastic waves simultaneously, and can be utilized in various fields such as optical, acoustic and acouto-optical devices, and cavity optomechanics. This paper firstly introduces the basic concepts of phoxonic crystals, including the constituting materials, their classifications according to spatial periodicity, the numerical calculation methods of band structures. We elaborate the characteristics of phoxonic dual bandgaps for different systems, and the topology optimization method applied in optimizing the bandgap width of phoxonic dual bandgaps. The field of cavity optomechanics, as well as the quasistatic method and optomechanical coupling coefficient method for evaluating the acousto-optical coupling strength are introduced. The acousto-optical coupling phenomena in various phoxonic crystal structures are summarized. Then this paper introduces the research works related to phoxonic crystal waveguides and sensors. Finally, we outline the prospects of phoxonic crystals based on state of the art, including the enhancements of acousto-optical interaction in phoxonic crystal cavities, the investigations of three-dimensional phoxonic crystals, the designs of different phoxonic metamaterials, the phoxonic crystal device designs and related applications, and so on.

Phonon interaction with coupled photonic-plasmonic modes in a phoxonic cavity

We present a theoretical investigation of the acousto-optic interaction in a two-dimensional phoxonic crystal cavity containing a metallic nanowire. The crystal is constituted by a square array of cylindrical holes in a TiO2 matrix containing a cavity inside which a gold nanowire is introduced. The optical modes of the cavity are therefore of combined photonic-plasmonic character. We calculate the strength of coupling between these modes and the localized phonons of the cavity, based on the “Moving Interface” mechanism of acousto-optic coupling. We discuss the coupling strength as a function of the size and position of the metallic nanowire and compare the results with those of a cavity without metallic particle.

Enhancement of acousto-optical coupling in two-dimensional air-slot phoxonic crystal cavities by utilizing surface acoustic waves

A phoxonic crystal is a periodically patterned material that can simultaneously localize optical and acoustic modes. The acousto-optical coupling in two-dimensional air-slot phoxonic crystal cavities is investigated numerically. The photons can be well confined in the slot owing to the large electric field discontinuity at the air/dielectric interfaces. Besides, the surface acoustic modes lead to the localization of the phonons near the air-slot. The high overlap of the photonic and phononic cavity modes near the slot results in a significant enhancement of the moving interface effect, and thus strengthens the total acousto-optical interaction. The results of two cavities with different slot widths show that the coupling strength is dependent on the slot width. It is expected to achieve a strong acousto-optical/optomechanical coupling in air-slot phoxonic crystal structures by utilizing surface acoustic modes.

Acousto-optic couplings in two-dimensional Lithium Niobate phoXonic crystal

We investigate the acousto-optic couplings in two-dimensional infinite piezoelectric phoXonic crystal cavities. The periodic structure considered consists in a square array of air inclusions drilled in Lithium Niobate matrix. This structure allows the simultaneous confinement of acoustic and optic waves in a point defect obtained by removing one hole from the structure. Our theoretical analysis takes into account three different coupling mechanisms. In addition to the traditional effects: photo-elastic effect and opto-mechanic effect existing in non-piezoelectric materials, we consider the electro-optic effect introduced by the electric field accompanying the phonon. Using the finite element method, we analyze the perturbation of the photonic cavity modes under the action of phononic cavity modes. We first discuss some aspects of the additional electro-optic effect. For illustration purposes, we compare the coupling strength of two analogous breathing modes, one as found in the LiNbO3 structure and another mode qualitatively comparable but evidenced in a similar silicon structure. Then, we end the discussion by an analysis of the coupling strength dependence on typical crystallographic cuts of Lithium Niobate.

Modeling of optomechanical coupling in a phoxonic crystal cavity in diamond.

A photonic and phononic crystal (phoxonic crystal PxC) is a periodically patterned material that can at the same time localize optical and mechanical modes. Here we theoretically model one-dimensional PxC in diamond and find high quality mechanical resonances with very high frequencies > 10 GHz and optical properties comparable to those of PxC in other materials. The simultaneous confinement of photons and phonons leads to an optomechanical interaction that we calculate in a perturbation approach. The optomechanical coupling strengths reach values in the MHz range. We identify design rules to simultaneously achieve high optical and mechanical quality factors along with strong optomechanical coupling.

Acousto-optic couplings in two-dimensional phoxonic crystal cavities

We investigate the acousto-optic coupling, based on both photo-elastic and opto-mechanical mechanisms, in periodic structures with simultaneous photonic and phononic band gaps. The investigations are focused on a cavity defect in which the strong confinement of acoustic and optic waves enhances the interaction. We calculate the modulation of each photonic mode frequency by each phononic mode confined in the cavity. We compare the strength for the photo-elastic and opto-mechanical effects in the different cases. Both mechanisms can be in phase or out of phase and produce additive or subtractive effects in the total acousto-optic coupling.