scholarly journals A Convenient Way to Determine the Optimum Angle of Incidence of Fizeau Interferometer

2021 ◽  
Vol 11 (22) ◽  
pp. 10678
Author(s):  
Bowen Du ◽  
Yuquan Zheng ◽  
Chao Lin ◽  
Hang Zhang
Keyword(s):  
Incidence Angle ◽  
Incident Angle ◽  
Wedge Angle ◽  
Normal Incidence ◽  
Angle Of Incidence ◽  
Fizeau Interferometer ◽  
Optimal Angle ◽  
Suppression Effect ◽  
Estimation Formula ◽  
Modified Method

In a Fizeau interferometer, off-axis illumination will lead to fringe optimization. Primarily due to the unique structure of our interferometer, we first analyze the influence of the optical properties of the parallel plate as a part of the interferometer on the optimal incident angle. Generally, the incident angle determination is mainly based on the graphing method proposed by Langenbeck and the estimation formula proposed by Kajava. However, Langenbeck’s method is cumbersome, and the error of Kajava’s estimation formula is large. Based on the predecessors, this paper proposes a modified method of determining the optimal angle of incidence and further derives more accurate optimal angle expressions than Kajava’s. By simply substituting the wedge angle of the wedge cavity and the reflectivity of the cavity, the optimum incidence angle can be obtained immediately. Thus, it eliminates the tedious and complex process of finding the optimum incident angle by graphing method and makes the formula method the simplest method to find the optimum incident angle. Finally, the comparison of the interference intensity at the optimum incidence angle calculated by the improved method and normal incidence is given. It is found that the beam has a good suppression effect on the sub-peak when it is incident at the optimum incident angle calculated by the method in this paper.

scholarly journals An Ultrathin, Triple-Band Metamaterial Absorber with Wide-Incident-Angle Stability for Conformal Applications at X and Ku Frequency Band

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Guangsheng Deng ◽  
Kun Lv ◽  
Hanxiao Sun ◽  
Jun Yang ◽  
Zhiping Yin ◽  
...  
Keyword(s):  
Free Space ◽  
High Efficiency ◽  
Incident Angle ◽  
Surface Current ◽  
Normal Incidence ◽  
Metamaterial Absorber ◽  
Angle Of Incidence ◽  
Perfect Absorption ◽  
Absorption Frequency ◽  
Unit Cells

AbstractAn ultrathin and flexible metamaterial absorber (MA) with triple absorption peaks is presented in this paper. The proposed absorber has been designed in such a way that three absorption peaks are located at 8.5, 13.5, and 17 GHz (X and Ku bands) with absorption of 99.9%, 99.5%, and 99.9%, respectively. The proposed structure is only 0.4 mm thick, which is approximately 1/88, 1/55, and 1/44 for the respective free space wavelengths of absorption frequency in various bands. The MA is also insensitive due to its symmetric geometry. In addition, the proposed structure exhibits minimum 86% absorption (TE incidence) within 60° angle of incidence. For TM incidence, the proposed absorber exhibits more than 99% absorptivity up to 60° incidence. Surface current and electric field distributions were investigated to analyze the mechanism governing absorption. Parameter analyses were performed for absorption optimization. Moreover, the performance of the MA was experimentally demonstrated in free space on a sample under test with 20 × 30 unit cells fabricated on a flexible dielectric. Under normal incidence, the fabricated MA exhibits near perfect absorption at each absorption peak for all polarization angles, and the experimental results were found to be consistent with simulation results. Due to its advantages of high-efficiency absorption over a broad range of incidence angles, the proposed absorber can be used in energy harvesting and electromagnetic shielding.

scholarly journals Polarization-Sensitive and Wide Incidence Angle-Insensitive Fabry–Perot Optical Cavity Bounded by Two Metal Grating Layers

Sensors ◽  
2020 ◽  
Vol 20 (18) ◽  
pp. 5382
Author(s):  
Jehwan Hwang ◽  
Zahyun Ku ◽  
Jiyeon Jeon ◽  
Yeongho Kim ◽  
Deok-Kee Kim ◽  
...  
Keyword(s):  
Incidence Angle ◽  
Incident Angle ◽  
Incident Light ◽  
Extinction Ratio ◽  
Cavity Resonance ◽  
Angle Of Incidence ◽  
Metal Grating ◽  
Imaging Array ◽  
Fabry Perot ◽  
Polarimetric Imaging

Infrared (IR) polarimetric imaging has attracted attention as a promising technology in many fields. Generally, superpixels consisting of linear polarizer elements at different angles plus IR imaging array are used to obtain the polarized target signature by using the detected polarization-sensitive intensities. However, the spatial arrangement of superpixels across the imaging array may lead to an incorrect polarimetric signature of a target, due to the range of angles from which the incident radiation can be collected by the detector. In this article, we demonstrate the effect of the incident angle on the polarization performance of an alternative structure where a dielectric layer is inserted between the nanoimprinted subwavelength grating layers. The well-designed spacer creates the Fabry–Perot cavity resonance, and thereby, the intensity of transverse-magnetic I-polarized light transmitted through two metal grating layers is increased as compared with a single-layer metal grating, whereas transverse-electric (TE)-transmitted light intensity is decreased. TM-transmittance and polarization extinction ratio (PER) of normally incident light of wavelength 4.5 μm are obtained with 0.49 and 132, respectively, as the performance of the stacked subwavelength gratings. The relative change of the PERs for nanoimprint-lithographically fabricated double-layer grating samples that are less than 6% at an angle of incidence up to 25°, as compared to the normal incidence. Our work can pave the way for practical and efficient polarization-sensitive elements, which are useful for many IR polarimetric imaging applications.

Reflection and Transmission of Longitudinal Displacement Wave through Micropolar Fluid Interlayer in Micropolar Solid

2013 ◽  
Vol 438-439 ◽  
pp. 408-412
Author(s):  
Song Yang Dang ◽  
Hong Yu Xu ◽  
Qing Yong Sun ◽  
Bin Liang
Keyword(s):  
Micropolar Fluid ◽  
Incidence Angle ◽  
Incident Angle ◽  
Normal Incidence ◽  
Grazing Incidence ◽  
Longitudinal Displacement ◽  
Reflection And Transmission ◽  
Transmitted Waves ◽  
Displacement Wave ◽  
Fluid Theory

Based on micropolar fluid theory and micropolar solid elasticity theory, reflection and transmission characteristics of longitudinal displacement wave and two coupled waves are studied when incident longitudinal displacement plane wave propagates through micropolar fluid interlayer in micropolar solid. Theoretical and numerical analytical results reveal that in general the amplitude ratios of various reflected and transmitted waves are functions of the incidence angle, the frequency of the incident wave and the material properties of the medium. At normal incidence, the reflection and transmission of only longitudinal waves take place and no coupled transverse wave is found to reflect or transmit. At grazing incidence, no reflection or transmission phenomena take place and the same wave propagates along the interface. The change rules of the amplitudes varied with incident angle are also discussed.

Unsteady Numerical Analysis of Flow Across 2D Cylinder

2010 ◽  
Author(s):  
Yaling Peng ◽  
Zhiguo Zhang ◽  
Fangliang Wu ◽  
Dakui Feng
Keyword(s):  
Strouhal Number ◽  
Excellent Agreement ◽  
Incidence Angle ◽  
Flow Direction ◽  
Incident Angle ◽  
Numerical Results ◽  
Published Data ◽  
Angle Of Incidence ◽  
Square Cylinder ◽  
Navier Stokes Equation

2-D computational analyses were conducted for unsteady viscous flow across cylinders of different geometries and different incident angle. Circular, square and elliptic (both at 0° and 90° angles of incidence) cylinders were examined. The calculations were performed by solving the unsteady 2-D Navier-Stokes equation at Re = 100. The calculated results produce drag and lift coefficients, as well as Strouhal number in excellent agreement with published data. Calculations for unsteady, incompressible 2D flow around a square cylinder at incidence angle of 0° and 45° and for Reynolds number = 100 were carried out. Cycle independence and grid independence results were obtained for the Strouhal number. The results were in excellent agreement with the available experimental and numerical results. Numerical results show that the Strouhal number increases with fluid angle of incidence on the cylinder. The wake behind the cylinder is wider and more violent for a square cylinder at 45° incidence compared to a square at 0° this is due to the increase in the characteristic length in the flow direction. The Strouhal number is highest for elliptic geometry among all cylinders in this research. For the geometries elliptic at 0° at Re = 100, there is not vortex shedding behind the cylinder. This is due to dominance of inertia forces over viscous forces. The present study was carried out for a 2-D single cylinder at fixed location inside a channel for unidirectional velocity. To get more accurate results computation on 3-D geometry should be carried out.

Electron Channeling Patterns

1977 ◽  
Vol 35 ◽  
pp. 12-13
Author(s):  
David C. Joy
Keyword(s):  
Electron Diffraction ◽  
Incidence Angle ◽  
Photographic Plate ◽  
Diffraction Effect ◽  
Angle Of Incidence ◽  
Bulk Single Crystal ◽  
Time Resolved ◽  
Electron Channeling ◽  
Spatially Resolved ◽  
Large Bulk

Electron channeling patterns (ECP) were first found by Coates (1967) while observing a large bulk, single crystal of silicon in a scanning electron microscope. The geometric pattern visible was shown to be produced as a result of the changes in the angle of incidence, between the beam and the specimen surface normal, which occur when the sample is examined at low magnification (Booker, Shaw, Whelan and Hirsch 1967).A conventional electron diffraction pattern consists of an angularly resolved intensity distribution in space which may be directly viewed on a fluorescent screen or recorded on a photographic plate. An ECP, on the other hand, is produced as the result of changes in the signal collected by a suitable electron detector as the incidence angle is varied. If an integrating detector is used, or if the beam traverses the surface at a fixed angle, then no channeling contrast will be observed. The ECP is thus a time resolved electron diffraction effect. It can therefore be related to spatially resolved diffraction phenomena by an application of the concepts of reciprocity (Cowley 1969).

On resolving fine periodic microstructures in the optical microscope

1989 ◽  
Vol 47 ◽  
pp. 364-365
Author(s):  
W.S. Putnam ◽  
C. Viney
Keyword(s):  
Liquid Crystalline ◽  
Numerical Aperture ◽  
Polarized Light ◽  
Normal Incidence ◽  
Optical Microscope ◽  
Angle Of Incidence ◽  
Resolution Limit ◽  
Crystalline Materials ◽  
Periodic Microstructures ◽  
Liquid Crystalline Materials

Many sheared liquid crystalline materials (fibers, films and moldings) exhibit a fine banded microstructure when observed in the polarized light microscope. In some cases, for example Kevlar® fiber, the periodicity is close to the resolution limit of even the highest numerical aperture objectives. The periodic microstructure reflects a non-uniform alignment of the constituent molecules, and consequently is an indication that the mechanical properties will be less than optimal. Thus it is necessary to obtain quality micrographs for characterization, which in turn requires that fine detail should contribute significantly to image formation.It is textbook knowledge that the resolution achievable with a given microscope objective (numerical aperture NA) and a given wavelength of light (λ) increases as the angle of incidence of light at the specimen surface is increased. Stated in terms of the Abbe resolution criterion, resolution improves from λ/NA to λ/2NA with increasing departure from normal incidence.

scholarly journals Towards Transabdominal Functional Photoacoustic Imaging of the Placenta: Improvement in Imaging Depth Through Optimization of Light Delivery

2021 ◽  
Author(s):  
Kristie Huda ◽  
Kenneth F. Swan ◽  
Cecilia T. Gambala ◽  
Gabriella C. Pridjian ◽  
Carolyn L. Bayer
Keyword(s):  
Delivery System ◽  
Light Propagation ◽  
Ex Vivo ◽  
Photoacoustic Imaging ◽  
Incidence Angle ◽  
Incident Angle ◽  
Placental Tissue ◽  
Light Delivery ◽  
Imaging Depth ◽  
The Impact

AbstractFunctional photoacoustic imaging of the placenta could provide an innovative tool to diagnose preeclampsia, monitor fetal growth restriction, and determine the developmental impacts of gestational diabetes. However, transabdominal photoacoustic imaging is limited in imaging depth due to the tissue’s scattering and absorption of light. The aim of this paper was to investigate the impact of geometry and wavelength on transabdominal light delivery. Our methods included the development of a multilayer model of the abdominal tissue and simulation of the light propagation using Monte Carlo methods. A bifurcated light source with varying incident angle of light, distance between light beams, and beam area was simulated to analyze the effect of light delivery geometry on the fluence distribution at depth. The impact of wavelength and the effects of variable thicknesses of adipose tissue and muscle were also studied. Our results showed that the beam area plays a major role in improving the delivery of light to deep tissue, in comparison to light incidence angle or distance between the bifurcated fibers. Longer wavelengths, with incident fluence at the maximum permissible exposure limit, also increases fluence within deeper tissue. We validated our simulations using a commercially available light delivery system and ex vivo human placental tissue. Additionally, we compared our optimized light delivery to a commercially available light delivery system, and conclude that our optimized geometry could improve imaging depth more than 1.6×, bringing the imaging depth to within the needed range for transabdominal imaging of the human placenta.

Low-Energy Ion Scattering Measurements from an Al-Pd-Mn Quasicrystal

2000 ◽  
Vol 643 ◽  
Author(s):  
R. Bastasz ◽  
C. J. Jenks ◽  
T. A. Lograsso ◽  
A. R. Ross ◽  
P. A. Thiel ◽  
...  
Keyword(s):  
Signal Intensity ◽  
Surface Composition ◽  
Incidence Angle ◽  
Local Environment ◽  
Forward Direction ◽  
Low Energy ◽  
Angle Of Incidence ◽  
Fold Axis ◽  
Ion Scattering ◽  
Low Energy Ion Scattering

AbstractEnergy-angle distributions of low-energy inert-gas ions scattered from surfaces provide information about surface composition and structure. We have measured energy spectra of He+ scattered from an Al71Pd20Mn9 quasicrystal, which was oriented perpendicular to the 5-fold axis, along various azimuthal directions. Strong scattering signals are seen from Al and Pd, but only a weak Mn signal is observed. From measurements made of He+ at an oblique angle of incidence scattered in the forward direction, we observe a 72° periodicity in the azimuthal dependence of the scattering signal intensity from Al surface atoms. The effect arises from shadowing effects involving neighboring surface atoms and provides direct evidence that Al surface atoms exist in a local environment with 5-fold symmetry. In addition, measuring the variation of the signal intensity with incidence angle provides information about neighboring atom distances, which compare favorably with a model of the quasicrystal surface derived from the bulk structure.

scholarly journals Method for fast determination of the angle of ionizing radiation incidence from data measured by a Timepix3 detector

2021 ◽  
Vol 10 (1) ◽  
pp. 63-70
Author(s):  
Felix Lehner ◽  
Jürgen Roth ◽  
Oliver Hupe ◽  
Marc Kassubeck ◽  
Benedikt Bergmann ◽  
...  
Keyword(s):  
Ionizing Radiation ◽  
Incidence Angle ◽  
Computation Time ◽  
Incident Radiation ◽  
Angle Of Incidence ◽  
Time Behavior ◽  
Calculation Algorithm ◽  
3D Geometry ◽  
Photon Event ◽  
Radiation Incidence

Abstract. This paper presents a method of how to determine spatial angles of ionizing radiation incidence quickly, using a Timepix3 detector. This work focuses on the dosimetric applications where detectors and measured quantities show significant angle dependencies. A determined angle of incidence can be used to correct for the angle dependence of a planar Timepix3 detector. Up until now, only passive dosemeters have been able to provide a correct dose and preserve the corresponding incidence angle of the radiation. Unfortunately, passive dosemeters cannot provide this information in “real” time. In our special setup we were able to retrieve the spatial angles with a runtime of less than 600 ms. Employing the new Timepix3 detector enables the use of effective data analysis where the direction of incident radiation is computed from a simple photon event map. In order to obtain this angle, we combine the information extracted from the map with known 3D geometry surrounding the detector. Moreover, we analyze the computation time behavior, conditions and optimizations of the developed spatial angle calculation algorithm.

scholarly journals Study of the Propagation Characteristics of Terahertz Waves in a Collisional and Inhomogeneous Dusty Plasma with a Ceramic Substrate and Oblique Angle of Incidence

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Qingwen Rao ◽  
Guanjun Xu ◽  
Pengfei Wang ◽  
Zhengqi Zheng
Keyword(s):  
Electron Density ◽  
Dusty Plasma ◽  
Collision Frequency ◽  
Incident Angle ◽  
Ceramic Substrate ◽  
Dust Particles ◽  
Angle Of Incidence ◽  
Oblique Angle ◽  
Terahertz Waves ◽  
Thz Wave

In this paper, the propagation properties of a terahertz (THz) wave in a collisional and inhomogeneous dusty plasma with a ceramic substrate and oblique angle of incidence are studied using the scattering matrix method. The influence of the various corresponding parameters, such as the frequency of the THz wave, angle of incidence, electron density, radius and density of the dust particles, and the collision frequency, on the absorbance and transmittance is calculated. The results of the simulation indicate that an increase in the wave frequency increases the transmittance and decreases the absorbance. Moreover, the absorbance of a THz wave in a dusty plasma with a ceramic substrate increases with an increase in the incident angle, maximum electron density, coefficient of steepness, density and radius of the dust particles, and collision frequency. These results provide an important theoretical basis for the problem of communication blackout between ground and spacecraft.

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