Photonic Nanojets Produced by All-Dielectric and Hyperbolic Meta-Microspheres
Primary Faculty Mentor’s Name
Maxim Durach
Proposal Track
Student
Session Format
Poster
Abstract
Dielectric microspheres have emerged as an important working tool of photonics over the past few years. They serve as high-Q resonators for whispering gallery modes (WGMs) and are able to produce tight and high intensity beams, called photonic nanojets (PNJs), in non-resonant regimes upon plane-wave illumination. PNJs have been observed in the shadow region of a number of dielectric objects such as core-shell microspheres, microcylinders, microcubes, concentric-ring-decorated microspheres and the like. These structures were found to have numerous applications in spectroscopy, lithography, and imaging on the nanoscale.
Photonic metamaterials have been a major research field for almost two decades with the primary aspirations being superlensing and cloaking. One common type of metamaterial is a one-dimensional metal-dielectric array, which exhibits a wide range of phenomena, including various optical responses. Generally modeled as uniaxial anisotropic media, depending on the signs of the real parts of dielectric permittivities, the uniaxial metamaterials can behave as anisotropic dielectrics, hyperbolic materials, or anisotropic metals. A large variety of optical responses supported by these metamaterial structures comes with this range of optical properties.
We investigate a novel metamaterial structure – a metamaterial microsphere, which is composed of subwavelength spherical shells of two different materials alternating in an onion-layer fashion. The resonant properties of this structure have attracted considerable attention over the last year and the corresponding WGMs have been described. We focus on non-resonant optical properties of the meta-microspheres, and the formation of PNJs in this work.
The optical responses of such meta-microspheres can be described by the effective medium approximation, in which the dielectric permittivity tensor is diagonal in spherical coordinates with different values of permittivities in radial and angular directions. We consider two regimes – an all-dielectric regime, when both radial and angular permittivities are positive, and the hyperbolic regime, when radial permittivity is negative, while angular permittivity is positive. The electromagnetic fields in this structure can be described using the framework of Mie theory adapted to the anisotropic material under consideration. Our results indicate that the introduction of metallic response along the radial direction is analogous to an effective decrease of the aperture associated with the meta-microsphere.
Keywords
microspheres, metamaterials, hyperbolic materials, photonic nanojets, all-dielectric photonics
Location
Concourse and Atrium
Presentation Year
2015
Start Date
11-7-2015 2:10 PM
End Date
11-7-2015 3:20 PM
Publication Type and Release Option
Presentation (Open Access)
Recommended Citation
Hodges, Reed M.; Dean, Cleon E.; and Durach, Maxim, "Photonic Nanojets Produced by All-Dielectric and Hyperbolic Meta-Microspheres" (2015). Georgia Undergraduate Research Conference (2014-2015). 10.
https://digitalcommons.georgiasouthern.edu/gurc/2015/2015/10
Photonic Nanojets Produced by All-Dielectric and Hyperbolic Meta-Microspheres
Concourse and Atrium
Dielectric microspheres have emerged as an important working tool of photonics over the past few years. They serve as high-Q resonators for whispering gallery modes (WGMs) and are able to produce tight and high intensity beams, called photonic nanojets (PNJs), in non-resonant regimes upon plane-wave illumination. PNJs have been observed in the shadow region of a number of dielectric objects such as core-shell microspheres, microcylinders, microcubes, concentric-ring-decorated microspheres and the like. These structures were found to have numerous applications in spectroscopy, lithography, and imaging on the nanoscale.
Photonic metamaterials have been a major research field for almost two decades with the primary aspirations being superlensing and cloaking. One common type of metamaterial is a one-dimensional metal-dielectric array, which exhibits a wide range of phenomena, including various optical responses. Generally modeled as uniaxial anisotropic media, depending on the signs of the real parts of dielectric permittivities, the uniaxial metamaterials can behave as anisotropic dielectrics, hyperbolic materials, or anisotropic metals. A large variety of optical responses supported by these metamaterial structures comes with this range of optical properties.
We investigate a novel metamaterial structure – a metamaterial microsphere, which is composed of subwavelength spherical shells of two different materials alternating in an onion-layer fashion. The resonant properties of this structure have attracted considerable attention over the last year and the corresponding WGMs have been described. We focus on non-resonant optical properties of the meta-microspheres, and the formation of PNJs in this work.
The optical responses of such meta-microspheres can be described by the effective medium approximation, in which the dielectric permittivity tensor is diagonal in spherical coordinates with different values of permittivities in radial and angular directions. We consider two regimes – an all-dielectric regime, when both radial and angular permittivities are positive, and the hyperbolic regime, when radial permittivity is negative, while angular permittivity is positive. The electromagnetic fields in this structure can be described using the framework of Mie theory adapted to the anisotropic material under consideration. Our results indicate that the introduction of metallic response along the radial direction is analogous to an effective decrease of the aperture associated with the meta-microsphere.
