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10 pages, 4085 KB

Open AccessCommunication

Laser Diffraction Zones and Spots from Three-Dimensional Graded Photonic Super-Crystals and Moiré Photonic Crystals

by Noah Hurley, Steve Kamau, Khadijah Alnasser, Usha Philipose, Jingbiao Cui and Yuankun Lin

Photonics 2022, 9(6), 395; https://doi.org/10.3390/photonics9060395 - 3 Jun 2022

Cited by 5 | Viewed by 4719

The laser diffraction from periodic structures typically shows isolated and sharp point patterns at zeroth and ±nth orders. Diffraction from 2D graded photonic super-crystals (GPSCs) has demonstrated over 1000 spots due to the fractional diffractions. Here, we report the holographic fabrication of three [...] Read more.

The laser diffraction from periodic structures typically shows isolated and sharp point patterns at zeroth and ±nth orders. Diffraction from 2D graded photonic super-crystals (GPSCs) has demonstrated over 1000 spots due to the fractional diffractions. Here, we report the holographic fabrication of three types of 3D GPSCs through nine beam interferences and their characteristic diffraction patterns. The diffraction spots due to the fractional orders are merged into large-area diffraction zones for these three types of GPSCs. Three distinguishable diffraction patterns have been observed: (a) 3 × 3 Diffraction zones for GPSCs with a weak gradient in unit super-cell, (b) 5 × 5 non-uniform diffraction zones for GPSCs with a strong modulation in long period and a strong gradient in unit super-cell, (c) more than 5 × 5 uniform diffraction zones for GPSCs with a medium gradient in unit super-cell and a medium modulation in long period. The GPSCs with a strong modulation appear as moiré photonic crystals. The diffraction zone pattern not only demonstrates a characterization method for the fabricated 3D GPSCs, but also proves their unique optical properties of the coupling of light from zones with 360° azimuthal angles and broad zenith angles. Full article

(This article belongs to the Special Issue Photonic Crystals: Physics and Devices)

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10 pages, 38270 KB

Open AccessArticle

Photonic Band Gaps and Resonance Modes in 2D Twisted Moiré Photonic Crystal

by Khadijah Alnasser, Steve Kamau, Noah Hurley, Jingbiao Cui and Yuankun Lin

Photonics 2021, 8(10), 408; https://doi.org/10.3390/photonics8100408 - 23 Sep 2021

Cited by 10 | Viewed by 5879

Abstract

The study of twisted bilayer 2D materials has revealed many interesting physics properties. A twisted moiré photonic crystal is an optical analog of twisted bilayer 2D materials. The optical properties in twisted photonic crystals have not yet been fully elucidated. In this paper, [...] Read more.

The study of twisted bilayer 2D materials has revealed many interesting physics properties. A twisted moiré photonic crystal is an optical analog of twisted bilayer 2D materials. The optical properties in twisted photonic crystals have not yet been fully elucidated. In this paper, we generate 2D twisted moiré photonic crystals without physical rotation and simulate their photonic band gaps in photonic crystals formed at different twisted angles, different gradient levels, and different dielectric filling factors. At certain gradient levels, interface modes appear within the photonic band gap. The simulation reveals “tic tac toe”-like and “traffic circle”-like modes as well as ring resonance modes. These interesting discoveries in 2D twisted moiré photonic crystal may lead toward its application in integrated photonics. Full article

(This article belongs to the Special Issue Design and Application of Modern Evanescent Wave Photonic Sensors)

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10 pages, 2306 KB

Open AccessCommunication

Broadband Absorption in Patterned Metal/Weakly-Absorbing-Spacer/Metal with Graded Photonic Super-Crystal

by Steve Kamau, Safaa Hassan, Khadijah Alnasser, Hualiang Zhang, Jingbiao Cui and Yuankun Lin

Photonics 2021, 8(4), 114; https://doi.org/10.3390/photonics8040114 - 8 Apr 2021

Cited by 2 | Viewed by 3000

Abstract

It is challenging to realize the complete broadband absorption of near-infrared in thin optical devices. In this paper, we studied high light absorption in two devices: a stack of Au-pattern/insulator/Au-film and a stack of Au-pattern/weakly-absorbing-material/Au-film where the Au-pattern was structured in graded photonic [...] Read more.

It is challenging to realize the complete broadband absorption of near-infrared in thin optical devices. In this paper, we studied high light absorption in two devices: a stack of Au-pattern/insulator/Au-film and a stack of Au-pattern/weakly-absorbing-material/Au-film where the Au-pattern was structured in graded photonic super-crystal. We observed multiple-band absorption, including one near 1500 nm, in a stack of Au-pattern/spacer/Au-film. The multiple-band absorption is due to the gap surface plasmon polariton when the spacer thickness is less than 30 nm. Broadband absorption appears in the near-infrared when the insulator spacer is replaced by a weakly absorbing material. E-field intensity was simulated and confirmed the formation of gap surface plasmon polaritons and their coupling with Fabry–Pérot resonance. Full article

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8 pages, 3285 KB

Open AccessEditor’s ChoiceArticle

Generation of over 1000 Diffraction Spots from 2D Graded Photonic Super-Crystals

by Safaa Hassan, Yan Jiang, Khadijah Alnasser, Noah Hurley, Hualiang Zhang, Usha Philipose and Yuankun Lin

Photonics 2020, 7(2), 27; https://doi.org/10.3390/photonics7020027 - 10 Apr 2020

Cited by 4 | Viewed by 4085

Abstract

For the first time, we are able to generate over 1000 diffraction spots from a graded photonic super-crystal with a unit super-cell size of 12a × 12a where a is the lattice constant and hole radii are gradually changed in dual directions. The [...] Read more.

For the first time, we are able to generate over 1000 diffraction spots from a graded photonic super-crystal with a unit super-cell size of 12a × 12a where a is the lattice constant and hole radii are gradually changed in dual directions. The diffraction pattern from the graded photonic super-crystal reveals unique diffraction properties. The first order diffractions of (±1,0) or (0,±1) disappear. Fractional diffraction orders are observed in the diffraction pattern inside a square with vertices of (1,1), (1,−1), (−1,−1) and (−1,−1). The fractional diffraction can be understood from lattices with a period of a. However, a dual-lattice model is considered in order to explain higher-order diffractions. E-field intensity simulations show a coupling and re-distribution among fractional orders of Bloch waves. There are a total of 12 × 12 spots in E-field intensity in the unit supercell corresponding to 12 × 12 fractional diffraction orders in the diffraction pattern and 12 × 12 fractional orders of momentum in the first Brillouin zone in k-space. Full article

(This article belongs to the Special Issue Advanced Optical Materials and Devices)

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8 pages, 2492 KB

Open AccessArticle

Effects of Photonic Band Structure and Unit Super-Cell Size in Graded Photonic Super-Crystal on Broadband Light Absorption in Silicon

by Safaa Hassan, Khadijah Alnasser, David Lowell and Yuankun Lin

Photonics 2019, 6(2), 50; https://doi.org/10.3390/photonics6020050 - 9 May 2019

Cited by 8 | Viewed by 4517

Abstract

The newly discovered graded photonic super-crystal (GPSC) with a large size of unit cell can have novel optical properties that have not been explored. The unit super-cell in the GPSC can be designed to be large or small and thus the GPSC can [...] Read more.

The newly discovered graded photonic super-crystal (GPSC) with a large size of unit cell can have novel optical properties that have not been explored. The unit super-cell in the GPSC can be designed to be large or small and thus the GPSC can have no photonic band gap or several gaps. The photonic band structures in Si GPSC can help predict the light absorption in Si. Photonic resonance modes help enhance the absorption of light in silicon; however, photonic band gaps decrease the absorption for light with a large incident angle. The Si device patterned in GPSC with a unit super-cell of 6a × 6a (a is a lattice constant in traditional photonic crystal) has a broadband high absorption with strong incident-angular dependence. The device with the unit super-cell of 12a × 12a has relatively low light absorption with weak incident-angle dependence. The Si GPSC with a unit super-cell of 8a × 8a combines both advantages of broadband high absorption and weak dependence of absorption on the incident angle. Full article

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10 pages, 2916 KB

Open AccessArticle

Holographic Fabrication and Optical Property of Graded Photonic Super-Crystals with a Rectangular Unit Super-Cell

by Safaa Hassan, Oliver Sale, David Lowell, Noah Hurley and Yuankun Lin

Photonics 2018, 5(4), 34; https://doi.org/10.3390/photonics5040034 - 11 Oct 2018

Cited by 15 | Viewed by 3979

Abstract

Recently developed graded photonic super-crystals show an enhanced light absorption and light extraction efficiency if they are integrated with a solar cell and an organic light emitting device, respectively. In this paper, we present the holographic fabrication of a graded photonic super-crystal with [...] Read more.

Recently developed graded photonic super-crystals show an enhanced light absorption and light extraction efficiency if they are integrated with a solar cell and an organic light emitting device, respectively. In this paper, we present the holographic fabrication of a graded photonic super-crystal with a rectangular unit super-cell. The spatial light modulator-based pixel-by-pixel phase engineering of the incident laser beam provides a high resolution phase pattern for interference lithography. This also provides a flexible design for the graded photonic super-crystals with a different ratio of length over the width of the rectangular unit super-cell. The light extraction efficiency is simulated for the organic light emitting device, where the cathode is patterned with the graded photonic super-crystal. The high extraction efficiency is maintained for different exposure thresholds during the interference lithography. The desired polarization effects are observed for certain exposure thresholds. The extraction efficiency reaches as high as 75% in the glass substrate. Full article

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9 pages, 2791 KB

Open AccessArticle

Extraordinary Light-Trapping Enhancement in Silicon Solar Cell Patterned with Graded Photonic Super-Crystals

by Safaa Hassan, David Lowell, Murthada Adewole, David George, Hualiang Zhang and Yuankun Lin

Photonics 2017, 4(4), 50; https://doi.org/10.3390/photonics4040050 - 20 Dec 2017

Cited by 13 | Viewed by 5264

Abstract

Light-trapping enhancement in newly discovered graded photonic super-crystals (GPSCs) with dual periodicity and dual basis is herein explored for the first time. Broadband, wide-incident-angle, and polarization-independent light-trapping enhancement was achieved in silicon solar cells patterned with these GPSCs. These super-crystals were designed by [...] Read more.

Light-trapping enhancement in newly discovered graded photonic super-crystals (GPSCs) with dual periodicity and dual basis is herein explored for the first time. Broadband, wide-incident-angle, and polarization-independent light-trapping enhancement was achieved in silicon solar cells patterned with these GPSCs. These super-crystals were designed by multi-beam interference, rendering them flexible and efficient. The optical response of the patterned silicon solar cell retained Bloch-mode resonance; however, light absorption was greatly enhanced in broadband wavelengths due to the graded, complex unit super-cell nanostructures, leading to the overlap of Bloch-mode resonances. The broadband, wide-angle light coupling and trapping enhancement mechanism are understood to be due to the spatial variance of the index of refraction, and this spatial variance is due to the varying filling fraction, the dual basis, and the varying lattice constants in different directions. Full article

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