ABSTRACT
A simple configuration of only λ/9 thick 2D metallic grating embedded within an electro-optic (EO) material (lithium niobate for instance) is proposed and theoretically studied to act as an EO modulator. On the one hand, this grating is used as an interdigitated comb to apply a very high and spatially periodic modification of the electrostatic field. On the other hand, the grating is designed to exhibit a Fano-like resonance in the NIR spectral range. This resonance is used to confine the electromagnetic field inside the EO material leading to an intrinsic enhancement of the EO effect. Extensive numerical simulations are performed to optimize the geometry in agreement with technological fabrication constraints. We achieved a local field factor of 24.5 leading to a local index modification Δn as large as 1 for 1 V applied voltage. This allows a modulation sensitivity of 14.35 nm/V (2000 times larger than state of the art) together with a resonance depth of 60% and a driving voltage of only 75 mV opening the way to the fabrication of ultra-thin low driving voltage EO devices.
ABSTRACT
Over the last few years, optical nanoantennas are continuously attracting interest owing to their ability to efficiently confine, localize resonance, and significantly enhanced electromagnetic fields at a subwavelength scale. However, such strong confinement can be further enhanced by using an appropriate combination of optical nanoantennas and Slanted Bound states in the continuum cavities. Here, we propose to synergistically bridge the plasmonic nanoantennas and high optical quality-factor cavities to numerically demonstrate six orders of magnitude local intensity enhancement without critical coupling conditions. The proposed hybrid system paves a new way for applications requiring highly confined fields such as optical trapping, optical sensing, nonlinear optics, quantum optics, etc.
ABSTRACT
A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.
ABSTRACT
In this paper, we propose and numerically simulate a novel optical trapping process based on the enhancement and the confinement of both magnetic and electric near-fields by using gold Diabolo Antenna (DA). The later was recently proposed to generate huge magnetic near-field when illuminated by linearly polarized wave along its axis. Numerical 3D - FDTD simulation results demonstrate the high confinement of the electromagnetic field in the vicinity of the DA. This enhancement is then exploited for the trapping of nano-particles (NP) as small as 30 nm radius. Results show that the trapping process greatly depends on the particle dimensions and that three different regimes of, trapping at contact, trapping without contact, or pushing can be achieved within the same DA. This doubly resonant structure opens the way to the design of a novel generation of efficient optical nano-tweezers that allow manipulation of nano-particles by simply changing the operation wavelength.
ABSTRACT
Scanning Near-field Optical Microscopy (SNOM) has been successful in finely tuning the optical properties of photonic crystal (PC) nanocavities. The SNOM nanoprobes proposed so far allowed for either redshifting or blueshifting the resonance peak of the PC structures. In this paper, we theoretically demonstrate the possibility of a redshifting (up to +0.65 nm) and a blueshifting (up to -5 nm) the PC cavity resonance wavelength with a single perturbation element. As an example, a fiber bowtie-aperture nano-antenna (BNA) engraved at the apex of a SNOM tip is proposed to play this role. The double-way tunability is the result of a competition between an induced electric dipole (BNA at resonance) leading to a redshift and an induced magnetic dipole (the tip metalcoating) giving rise to a blueshift of the resonance wavelength. We demonstrate that the sign of the spectral shift can be simply controlled through the tip-to-cavity distance. This study opens the way to the full postproduction control of the resonance wavelength of high quality-factor optical cavities.
ABSTRACT
We numerically demonstrate a drastic enhancement of the light intensity in the vicinity of the gap of Bowtie Nano-antenna (BA) through its coupling with Photonic Crystal (PC) resonator. The resulting huge energy transfer toward the BA is based on the coupling between two optical resonators (BA and PC membrane) of strongly unbalanced quality factors. Thus, these two resonators are designed so that the PC is only slightly perturbed in term of resonance properties. The proposed hybrid dielectric-plasmonic structure may open new avenues in the generation of deeply subwavelength intense optical sources, with direct applications in various domains such as data storage, non-linear optics, optical trapping and manipulation, microscopy, etc.
ABSTRACT
We show that the near-field coupling between a photonic crystal microlaser and a nano-antenna can enable hybrid photonic systems that are both physically compact (free from bulky optics) and efficient at transferring optical energy into the nano-antenna. Up to 19% of the laser power from a micron-scale photonic crystal laser cavity is experimentally transferred to a bowtie aperture nano-antenna (BNA) whose area is 400-fold smaller than the overall emission area of the microlaser. Instead of a direct deposition of the nano-antenna onto the photonic crystal, it is fabricated at the apex of a fiber tip to be accurately placed in the microlaser near-field. Such light funneling within a hybrid structure provides a path for overcoming the diffraction limit in optical energy transfer to the nanoscale and should thus open promising avenues in the nanoscale enhancement and confinement of light in compact architectures, impacting applications such as biosensing, optical trapping, local heating, spectroscopy, and nanoimaging.
ABSTRACT
We propose a new concept of fiber-integrated optical nano-tweezer on the basis of a single bowtie-aperture nano-antenna (BNA) fabricated at the apex of a metal-coated SNOM tip. We demonstrate 3D optical trapping of 0.5 micrometer latex beads with input power which does not exceed 1 mW. Optical forces induced by the BNA on tip are then analyzed numerically. They are found to be 10(3) times larger than the optical forces of a circular aperture of the same area. Such a fiber nanostructure provides a new path for manipulating nano-objects in a compact, flexible and versatile architecture and should thus open promising perspectives in physical, chemical and biomedical domains.
ABSTRACT
The control and localization of light at sub-wavelength scale are theoretically demonstrated with a very simple sub-wavelength dimension structure. This is demonstrated through a peculiar structure that can support localized modes which are not linked to any plasmon resonance. It is based on the acronym "FEMTO" that is designed using 26 sub-wavelength rectangular apertures engraved into perfectly conducting metal screen. A polarization-sensitive guided mode through these nano-apertures is at the origin of the light localization. Consequently, sub-wavelength light spots can be achieved with very simple structures illuminated by temporally shaped plane waves. Three parameters are temporally controlled for this purpose: the polarization, the wavelength and the amplitude of the incident beam. It is also demonstrated that replacing the perfect conductor by a real metal with dispersion leads to accentuate both the light confinement and its localization. These results open the path to the conception of optical nano-structures dedicated to sub-wavelength light addressing.
ABSTRACT
We suggest and numerically demonstrate a design for Frequency Selective Surfaces (FSS) operating in the optical (visible and near-infrared) range. The position and width of the FSS bandpass do not depend on the angle of incidence and polarization state of the incoming light, allowing high transmission at any angle. The FSS is formed by annular apertures perforated in a metal film and arranged in a square array. Angle- and polarization-independent transmission properties are demonstrated for silver. These results can be extended to other metals as well as to other frequency domains.
