Terahertz microscope with oblique subwavelength illumination: design principle

2022 ◽  
Vol 52 (1) ◽  
pp. 13-16
Author(s):  
O V Minin ◽  
I V Minin
Keyword(s):  
Design Principle ◽  
Optical Axis ◽  
Near Field ◽  
Incident Beam ◽  
Image Contrast ◽  
Beam Forming ◽  
Illumination Design ◽  
Oblique Illumination ◽  
Photonic Jet ◽  
Radiation Incidence

Abstract It is shown that the image contrast in the air when using a microscope based on dielectric microparticles with a size of the order of wavelength can be significantly enhanced with the help microparticles that provide the formation of the radiation localisation region at an angle to the direction of radiation incidence (at an angle to the optical axis). For this purpose, a screen is placed in front of the particle, which blocks part of the incident beam, forming a photonic hook or a photonic jet (terajet) with oblique illumination in the near field.

scholarly journals Super-Resolution Imaging with Patchy Microspheres

Photonics ◽  
2021 ◽  
Vol 8 (11) ◽  
pp. 513
Author(s):  
Qingqing Shang ◽  
Fen Tang ◽  
Lingya Yu ◽  
Hamid Oubaha ◽  
Darwin Caina ◽  
...  
Keyword(s):  
Colloidal Particle ◽  
Near Field ◽  
Super Resolution ◽  
Incident Beam ◽  
Diffraction Limit ◽  
Beam Forming ◽  
Feature Size ◽  
Disc Surface ◽  
Promising Tool ◽  
Resolution Imaging

The diffraction limit is a fundamental barrier in optical microscopy, which restricts the smallest resolvable feature size of a microscopic system. Microsphere-based microscopy has proven to be a promising tool for challenging the diffraction limit. Nevertheless, the microspheres have a low imaging contrast in air, which hinders the application of this technique. In this work, we demonstrate that this challenge can be effectively overcome by using partially Ag-plated microspheres. The deposited Ag film acts as an aperture stop that blocks a portion of the incident beam, forming a photonic hook and an oblique near-field illumination. Such a photonic hook significantly enhanced the imaging contrast of the system, as experimentally verified by imaging the Blu-ray disc surface and colloidal particle arrays.

Analysis of Contrast Reversal in SEM Images

1972 ◽  
Vol 30 ◽  
pp. 398-399
Author(s):  
M. D. Coutts ◽  
E. R. Levin
Keyword(s):  
Incident Beam ◽  
Normal Incidence ◽  
Beam Current ◽  
Secondary Emission ◽  
Image Contrast ◽  
Sem Images ◽  
Secondary Electrons ◽  
Image Position

On tilting samples in an SEM, the image contrast between two elements, x and y often decreases to zero at θε, which we call the no-contrast angle. At angles above θε the contrast is reversed, θ being the angle between the specimen normal and the incident beam. The available contrast between two elements, x and y, in the SEM can be defined as,(1)where ix and iy are the total number of reflected and secondary electrons, leaving x and y respectively. It can easily be shown that for the element x,(2)where ib is the beam current, isp the specimen absorbed current, δo the secondary emission at normal incidence, k is a constant, and m the reflected electron coefficient.

Image contrast in near‐field optics

1992 ◽  
Vol 71 (10) ◽  
pp. 4659-4663 ◽  
Author(s):  
J. K. Trautman ◽  
E. Betzig ◽  
J. S. Weiner ◽  
D. J. DiGiovanni ◽  
T. D. Harris ◽  
...  
Keyword(s):  
Near Field ◽  
Image Contrast ◽  
Near Field Optics

scholarly journals Plasmonic interference modulation for broadband nanofocusing

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Shaobo Li ◽  
Shuming Yang ◽  
Fei Wang ◽  
Qiang Liu ◽  
Biyao Cheng ◽  
...  
Keyword(s):  
Near Field ◽  
Three Dimensional ◽  
Field Enhancement ◽  
Incident Beam ◽  
Plasmonic Mode ◽  
Resonant Structures ◽  
Interference Modulation ◽  
Near Field Imaging ◽  
Linearly Polarized ◽  
Radially Polarized

Abstract Metallic plasmonic probes have been successfully applied in near-field imaging, nanolithography, and Raman enhanced spectroscopy because of their ability to squeeze light into nanoscale and provide significant electric field enhancement. Most of these probes rely on nanometric alignment of incident beam and resonant structures with limited spectral bandwidth. This paper proposes and experimentally demonstrates an asymmetric fiber tip for broadband interference nanofocusing within its full optical wavelengths (500–800 nm) at the nanotip with 10 nm apex. The asymmetric geometry consisting of two semicircular slits rotates plasmonic polarization and converts the linearly polarized plasmonic mode to the radially polarized plasmonic mode when the linearly polarized beam couples to the optical fiber. The three-dimensional plasmonic modulation induces circumference interference and nanofocus of surface plasmons, which is significantly different from the nanofocusing through plasmon propagation and plasmon evolution. The plasmonic interference modulation provides fundamental insights into the plasmon engineering and has important applications in plasmon nanophotonic technologies.

scholarly journals Microscope 3D Point Spread Function Evaluation Method on a Confirmed Object Plane Perpendicular to the Optical Axis

2020 ◽  
Vol 10 (7) ◽  
pp. 2430
Author(s):  
Shuai Mao ◽  
Zhenzhou Wang ◽  
Jinfeng Pan
Keyword(s):  
Point Spread Function ◽  
Evaluation Method ◽  
Optical Axis ◽  
Incident Beam ◽  
Function Evaluation ◽  
Object Plane ◽  
Point Spread ◽  
Spread Function ◽  
3D Point Spread Function

A point spread function evaluation method for a microscope on the object plane that is perpendicular to the optical axis is proposed. The measurement of the incident beam direction from the dual position-sensitive-detector (PSD)-based units, the determination of the object plane perpendicularity and the paraxial region, and evaluation methods for the point spread function (PSF) are presented and integrated into the proposed method. The experimental verification demonstrates that the proposed method can achieve a 3D PSF on the perpendicular object plane, as well as magnification, paraxial region evaluation, and confirmation for any microscopic system.

scholarly journals Terahertz Microscopy with Oblique Subwavelength Illumination in near Field

2021 ◽  
Author(s):  
Igor V. Minin ◽  
Oleg V. Minin
Keyword(s):  
Oblique Incidence ◽  
Near Field ◽  
Diffraction Limit ◽  
Terahertz Range ◽  
Promising Tool ◽  
Photonic Jet

Microscopes based on dielectric mesoscale particles, using the effect of a photonic jet or terajet in the terahertz range, are a promising tool for overcoming the diffraction limit. However, the image they generate has limited contrast, which limits the application of this method. In this letter, we demonstrate that it is possible to increase the contrast of an image based on dielectric mesoscale particles that provide the formation of photonic hooks. In this case, the illumination of the object is carried out by an oblique incidence of subwavelength terajet, which significantly (more than 2 times) increases the contrast of the image.

Design, simulation and experimental study of near-field beam forming techniques using conformal waveguide arrays

2010 ◽  
Vol 4 (2) ◽  
pp. 162 ◽  
Author(s):  
N.S. Karnik ◽  
R. Tulpule ◽  
M. Shah ◽  
P.S. Verma ◽  
C.Y. Huang ◽  
...  
Keyword(s):  
Experimental Study ◽  
Near Field ◽  
Beam Forming ◽  
Waveguide Arrays
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