Normal incidence narrowband transmission filtering capabilities using symmetry-protected modes of a subwavelength, dielectric grating

2015 ◽  
Vol 40 (11) ◽  
pp. 2637 ◽  
Author(s):  
Justin M. Foley ◽  
Jamie D. Phillips
Keyword(s):  
Normal Incidence ◽  
Dielectric Grating ◽  
Symmetry Protected

scholarly journals Polarization-selective modulation of supercavity resonances originating from bound states in the continuum

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Chan Kyaw ◽  
Riad Yahiaoui ◽  
Joshua A. Burrow ◽  
Viet Tran ◽  
Kyron Keelen ◽  
...  
Keyword(s):  
Strong Coupling ◽  
Bound States ◽  
Photonic Band Gap ◽  
Incidence Angle ◽  
Polarization State ◽  
Normal Incidence ◽  
Polarization Angle ◽  
Sensing Applications ◽  
Symmetry Protected ◽  
The Continuum

AbstractBound states in the continuum (BICs) are widely studied for their ability to confine light, produce sharp resonances for sensing applications and serve as avenues for lasing action with topological characteristics. Primarily, the formation of BICs in periodic photonic band gap structures are driven by symmetry incompatibility; structural manipulation or variation of incidence angle from incoming light. In this work, we report two modalities for driving the formation of BICs in terahertz metasurfaces. At normal incidence, we experimentally confirm polarization driven symmetry-protected BICs by the variation of the linear polarization state of light. In addition, we demonstrate through strong coupling of two radiative modes the formation of capacitively-driven Freidrich-Wintgen BICs, exotic modes which occur in off-Γ points not accessible by symmetry-protected BICs. The capacitance-mediated strong coupling at 0° polarization is verified to have a normalized coupling strength ratio of 4.17% obtained by the Jaynes-Cummings model. Furthermore, when the polarization angle is varied from 0° to 90° (0° ≤ ϕ < 90°), the Freidrich-Wintgen BIC is modulated until it is completely switched off at 90°.

Spatially and spectrally resolved ultra-narrowband TE-polarization absorber based on the guide-mode resonance

2017 ◽  
Vol 31 (24) ◽  
pp. 1750223
Author(s):  
Yan-Lin Liao ◽  
Yan Zhao ◽  
Xingfang Zhang ◽  
Wen Zhang ◽  
Zhongzhu Wang
Keyword(s):  
Normal Incidence ◽  
Optical Filters ◽  
Grating Period ◽  
Angle Measurement ◽  
Angular Width ◽  
Dielectric Grating ◽  
Guide Mode ◽  
Potential Applications ◽  
Polarization Electric Field ◽  
Spectrally Resolved

A spatially and spectrally resolved ultra-narrowband absorber with a dielectric grating and metal substrate has been reported. The absorber shows that the absorption rate is more than 0.99 with the absorption bandwidth less than 1.5 nm at normal incidence for TE polarization (electric field is parallel to grating grooves). The angular width of the absorption is about 0.27[Formula: see text]. The wavelength-angle sensitivity and absorption-angle sensitivity are 13.4 nm per degree and 296.3% per degree, respectively. The simulation results also show the spatially and spectrally resolved ultra-narrowband absorption is originated from the guide-mode resonance. In addition, the wavelength-angle sensitivity can be improved by enlarging the grating period according to the guide-mode resonance mechanism. The proposed absorber has potential applications in optical filters, angle measurement and thermal emitters.

scholarly journals Normal incidence filters using symmetry-protected modes in dielectric subwavelength gratings

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Xuan Cui ◽  
Hao Tian ◽  
Yan Du ◽  
Guang Shi ◽  
Zhongxiang Zhou
Keyword(s):  
Normal Incidence ◽  
Subwavelength Gratings ◽  
Symmetry Protected

scholarly journals A TM-Pass/TE-Stop Polarizer Based on a Surface Plasmon Resonance

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Yuu Wakabayashi ◽  
Junji Yamauchi ◽  
Hisamatsu Nakano
Keyword(s):  
Wavelength Range ◽  
Metal Film ◽  
Oblique Incidence ◽  
Extinction Ratio ◽  
Normal Incidence ◽  
Metal Films ◽  
Range Shifts ◽  
Dielectric Gratings ◽  
Dielectric Grating ◽  
Difference Time

A TM-pass/TE-stop polarizer consisting of a metal film sandwiched between dielectric gratings is investigated using the finite-difference time-domain method. At normal incidence with respect to the grating plane, a transmissivity of more than 94% and a reflectivity of more than 98% are obtained at  m for the TM and TE waves, respectively. The extinction ratio is more than 17 dB over a wavelength range of 1.50 m to 1.75 m. A high extinction ratio is maintained at oblique incidence, although the wavelength range shifts towards longer wavelengths. The TM-pass/TE-stop operation is also achieved with a modified structure, in which a dielectric grating is sandwiched between metal films.

Resonant dielectric-grating polarizers for normal incidence operation

2012 ◽  
Author(s):  
Kyu J. Lee ◽  
Jerry Giese ◽  
Laura Ajayi ◽  
Robert Magnusson ◽  
Eric Johnson
Keyword(s):  
Normal Incidence ◽  
Dielectric Grating

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.

Characterization of Rh/Si multilayer structure by HREM and HAADF

1992 ◽  
Vol 50 (1) ◽  
pp. 122-123
Author(s):  
Y. Cheng ◽  
J. Liu ◽  
M.B. Stearns ◽  
D.G. Steams
Keyword(s):  
Normal Incidence ◽  
High Resolution Electron Microscopy ◽  
X Rays ◽  
Beam Direction ◽  
Cross Sectional ◽  
Optical Elements ◽  
Resolution Electron ◽  
Point To Point ◽  
Better Than

The Rh/Si multilayer (ML) thin films are promising optical elements for soft x-rays since they have a calculated normal incidence reflectivity of ∼60% at a x-ray wavelength of ∼13 nm. However, a reflectivity of only 28% has been attained to date for ML fabricated by dc magnetron sputtering. In order to determine the cause of this degraded reflectivity the microstructure of this ML was examined on cross-sectional specimens with two high-resolution electron microscopy (HREM and HAADF) techniques.Cross-sectional specimens were made from an as-prepared ML sample and from the same ML annealed at 298 °C for 1 and 100 hours. The specimens were imaged using a JEM-4000EX TEM operating at 400 kV with a point-to-point resolution of better than 0.17 nm. The specimens were viewed along Si [110] projection of the substrate, with the (001) Si surface plane parallel to the beam direction.

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.

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