Ultra-compact, densely integrated optical components manufactured on a CMOS-foundry platform are highly desirable for optical information processing and electronic-photonic co-integration. However, the large spatial extent of evanescent waves arising from nanoscale confinement, ubiquitous in silicon photonic devices, causes significant cross-talk and scattering loss. Here, we demonstrate that anisotropic all-dielectric metamaterials open a new degree of freedom in total internal reflection to shorten the decay length of evanescent waves. We experimentally show the reduction of cross-talk by greater than 30 times and the bending loss by greater than 3 times in densely integrated, ultra-compact photonic circuit blocks. Our prototype all-dielectric metamaterial-waveguide achieves a low propagation loss of approximately 3.7±1.0 dB/cm, comparable to those of silicon strip waveguides. Our approach marks a departure from interference-based confinement as in photonic crystals or slot waveguides, which utilize nanoscale field enhancement. Its ability to suppress evanescent waves without substantially increasing the propagation loss shall pave the way for all-dielectric metamaterial-based dense integration.

We observe unique absorption resonances in silver/silica multilayer-based epsilon-near-zero (ENZ) metamaterials that are related to radiative bulk plasmon-polariton states of thin-films originally studied by Ferrell (1958) and Berreman (1963). In the local effective medium, metamaterial description, the unique effect of the excitation of these microscopic modes is counterintuitive and captured within the complex propagation constant, not the effective dielectric permittivities. Theoretical analysis of the band structure for our metamaterials shows the existence of multiple Ferrel-Berreman branches with slow light characteristics. The demonstration that the propagation constant reveals subtle microscopic resonances can lead to the design of devices where Ferrell-Berreman modes can be exploited for practical applications ranging from plasmonic sensing to imaging and absorption enhancement. Keywords: plasmon resonance, epsilon-near-zero, metamaterials, plasmonics An important class of artificial media are the epsilon-near-zero (ENZ) metamaterials that are designed to have a vanishing dielectric permittivity | | → 0. Waves propagating within ENZ media have a divergent phase velocity that can be used to guide light with zero phase advancement through sharp bends within sub-wavelength size channels [1, 2], or to tailor the phase of radiation/luminescence within a prescribed ENZ structure [3,4]. The electric field intensity within an ENZ medium can be enhanced relative to that in free space leading to strong light absorption [5]. This enhanced absorption in ENZ media has been exploited for novel polarization control and filtering in thin films [6], as well the proposal to use ENZ absorption resonances to tune thermal blackbody radiation of a heated object to the band-gap of a photovoltaic cell [7]. An enhanced non-linear response based upon strong spatial dispersion of waves in ENZ media has been demonstrated, and proposed for all-optical switching [8,9].Here we show theoretically and experimentally that ENZ metamaterials support unique absorption resonances related to radiative bulk plasmon-polaritons of thin metal films. These radiative bright modes exhibit properties in stark contrast to conventional dark modes of thin-film media (surface plasmon polaritons). The unique absorption resonances manifested in our metamaterials were originally studied by Ferrell in 1958 for plasmon-polaritonic thinfilms in the ultraviolet [10], and by Berreman in 1963 for phonon-polaritonic thin-films in the mid-infrared spectral region [11]. Surprisingly, two research communities have developed this independently with little communication or overlap until now: we therefore address these resonances as Ferrell-Berreman (FB) modes of our metamaterials. Counterintiutively, in the metamaterial effective medium picture, these resonances are not captured in the metamaterial dielectric permittivity constants but rather in the effective propagation constant. Furthermore, we show the existence of multiple branches of such FB modes that have slow ...

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For applications in sensing and cavity-based quantum computing and metrology, open-access Fabry-Perot cavities—with an air or vacuum gap between a pair of high reflectance mirrors—offer important advantages compared to other types of microcavities. For example, they are inherently tunable using MEMS-based actuation strategies, and they enable atomic emitters or target analytes to be located at high field regions of the optical mode. Integration of curved-mirror Fabry-Perot cavities on chips containing electronic, optoelectronic, and optomechanical elements is a topic of emerging importance. Micro-fabrication techniques can be used to create mirrors with small radius-of-curvature, which is a prerequisite for cavities to support stable, small-volume modes. We review recent progress towards chip-based implementation of such cavities, and highlight their potential to address applications in sensing and cavity quantum electrodynamics.