Highly confined photonic nanojet from elliptical particles (original) (raw)
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Photonic jet generated by spheroidal particle with Gaussian-beam illumination
Journal of the Optical Society of America B, 2014
Within the framework of generalized Lorenz-Mie theory, the properties of three-dimensional photonic jets emerging from spheroidal particles illuminated by a focused Gaussian beam are studied. The intensity, focal distance, and transverse and longitudinal dimensions of a photonic jet depending on the ellipticity of the spheroidal particle are numerically investigated. The simulation results show that, by simply varying the ellipticity, it is possible to obtain localized photon fluxes having different power characteristics and spatial dimensions. This can be of interest for several applications, such as high-resolution (nanometer scale) optical sensors, subdiffraction-resolution optical virtual imaging, and ultradirectional optical antennas.
Progress In Electromagnetics Research Letters, 2014
Some microobjects can concentrate an incoming incident plane wave and produce the socalled photonic nanojets. The highly focused emerging beams have a high intensity and can be used in applications in microscopy, beam manipulation and imaging. In this article, it is shown that an adequate choice of geometric shape and material can lead to an improvement of the electric field enhancement capacity of nanojets by a factor of 40%.
Optics Express, 2011
Photonic Nanojets are highly localized wave fields emerging directly behind dielectric microspheres; if suitably illuminated. In this contribution we reveal how different illumination conditions can be used to engineer the photonic Nanojets by measuring them in amplitude and phase with a high resolution interference microscope. We investigate how the wavelength, the amplitude distribution of the illumination, its polarization, or a break in symmetry of the axial-symmetric structure and the illumination affect the position, the localization and the shape of the photonic Nanojets. Various fascinating properties are systematically revealed and their implications for possible applications are discussed.
Integrated Optics: Devices, Materials, and Technologies XV, 2011
We experimentally engineer Nanojets produced by dielectric spheres by varying the illumination and observe the effect with a high-resolution interference microscope (HRIM). Converging and diverging spherical wavefronts and Bessel-Gauss beams are considered. We find that the diverging wavefront pushes Nanojets away from the surface of the sphere without change of the spot size. This allows earning several micrometers of working distance contrary to the Nanojet confined at the sphere's surface. When the radius of curvature of the incident wavefront is greater than about 5 times the sphere size, the Nanojet moves back to the sphere surface like it is found for plane wave incidence. On-axis Bessel-Gauss beam illumination with the central lobe covering the whole sphere leads to the same results as the plane wave case. Off-axis Bessel beam illumination can generate multiple-spot Nanojets. We demonstrate the separation of such spots of about 220 nm at 642 nm. This separation is smaller than the feature sizes defined by the diffraction limit at this wavelength. We discuss briefly applications of engineered Nanojets for nano-lithography and near-field sensing.
Photonic nanojet beam shaping by illumination polarization engineering
Optics Communications, 2020
Photonic Nanojets (PNJs) have attracted considerable research attention in the fields of super-resolution optical microscopy, nano-photolithography, and single molecule sensors because of their sub-wavelength near-field focusing properties. In this paper, we thoroughly studied how the polarizations and amplitude profiles of the incident beams affect the shape, size, and location of the PNJs generated from the illuminated microspheres. Numerical results showed that the PNJs generated by microspheres were strongly modulated by the polarizations and amplitude profiles of the illumination beams. Therefore, PNJs can be engineered according to the requirements of a specific application by designing the polarizations and amplitude profiles of the illumination light. Various fascinating properties of the PNJs generated with different illumination schemes were demonstrated and their implications for potential applications were discussed as well.
Journal of the Optical Society of America A, 2005
The detailed optics of photonic nanojets generated by normal plane-wave incidence on dielectric cylinders is discussed. These nanojets have a subwavelength beam waist and propagate with little divergence for several wavelengths. A physical explanation for this peculiar behavior is presented. Characteristic dimensions of the nanojets for a large range of physical parameters are calculated.
Elongated Photonic Nanojet from Truncated Cylindrical Zone Plate
Journal of Atomic, Molecular, and Optical Physics, 2012
Previously , it was shown that dielectric cylinder can form focal spots with small diameters and long depth. This type of focal spot was called photonic nanojet. In this paper, it was shown that dielectric cylinder of radius 595 nm (1.12 of wavelength) forms near the surface a photonic nanojet with diameter equal to 0.31 of wavelength and depth of focus equal to 0.57 of wavelength. Adding truncated concentric rings with radiuses equal to radiuses of zone plate to the cylinder increases the depth of focus to 1.18 of the wavelength. The diameter and intensity of focal spot near the cylinder surface remain unchanged.
Properties of photonic nanojet made of circular and elliptical dielectric cylinders
2020
In this paper, photonic nanojets are achieved using circular and elliptical dielectric cylinders in air background. Therefore, for obtaining high intensity and large focal length photonic nanojets, using highresolution finite difference time domain method, the optical properties of obtained nanojets are studied for all possible geometrical parameters. Numerical results show that the field intensity of circular photonic nanojet is higher than the elliptical one, while the focal length of elliptical photonic nanojet is greater than that of circular one. These results can be helpful in designing advanced photonic components such as ultra-sensitive particle sensors.
Optics Communications, 2018
Photonic nanojets (PNJs) owing to their sub-wavelength near-field features have found many interesting applications like nanoscopy, nano photolithography, high density optical storage, enhancement of Raman signal and single molecule spectroscopy etc. More recently, the focus of research has been on tailoring of PNJs either for better confinement and thus higher peak intensity or for elongation of nanojet for high resolution far field applications. In this paper, we show that crescent-shape refractive index profile (CSRP) of microspheres can be used to generate highly confined PNJ. By optimizing the refractive index of different layers in CSRP microsphere, we show a free space confinement down to ∼ ∕4.5 (FWHM ∼ 110 nm for excitation with 500 nm wavelength). Further, it was observed that the optical properties of substrates also modulate the PNJ characteristics and lead to a further improvement in the transverse confinement to ∼ ∕6.7.
Structured light engineering using a photonic nanojet
Optics letters, 2021
In this Letter, we present the photonic nanojet as a phenomenon in a structured light generator system that is implemented to modify the source focal spot size and emission angle. The optical system comprises a microlens array that is illuminated by a focused Gaussian beam to generate a structured pattern in the far field. By introducing a spheroid with different aspect ratios in the focus of the Gaussian beam, the source optical characteristics change, and a photonic nanojet is generated, which will engineer the far-field distribution. To probe the light fields, we implement a high-resolution interferometry setup to extract both the phase and intensity at different planes. We both numerically and experimentally demonstrate that the pattern distribution in the far field can be engineered by a photonic nanojet. As an example, we examine prolate, sphere, and oblate geometries. An interesting finding is that depending on the spheroid geometry, a smaller transverse FWHM of a photonic na...