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Displaying 26 - 50 of 53

Low-loss Metasurface Optics down to the Deep Ultraviolet

August 9, 2020
Author(s)
Cheng Zhang, Shawn M. Divitt, Qingbin Fan, Wenqi Zhu, Amit Agrawal, Yanqing Lu, Ting Xu, Henri Lezec
Metasurfaces, planar arrays of subwavelength electromagnetic structures that collectively mimic the functionality of much thicker conventional optical elements, have been demonstrated at frequencies ranging from the microwave up to the visible. Here, we

Broadband detection of multiple spin and orbital angular momenta via dielectric metasurface

July 26, 2020
Author(s)
Si Zhang, Pengcheng Huo, Wenqi Zhu, Cheng Zhang, Peng Chen, Mingze Liu, Lu Chen, Henri Lezec, Amit Agrawal, Yanqing Lu, Ting Xu
Light beams carrying spin angular momentum (SAM) and orbital angular momentum (OAM) have created novel opportunities in the areas of optical communications, imaging, micromanipulation and quantum optics. However, complex optical setups are required to

Chiroptical response of aluminum nano-crescents at ultraviolet wavelengths

April 21, 2020
Author(s)
Matthew S. Davis, Wenqi Zhu, Jared Strait, Jay K. Lee, Henri Lezec, Steve Blair, Amit Agrawal
Manipulation of plasmon modes at ultraviolet wavelengths using engineered nanophotonic devices allows for the development of high-sensitivity chiroptical spectroscopy systems. We present here a framework for the fabrication and characterization of Al based

Photonic spin-multiplexing metasurface for switchable spiral phase contrast imaging

March 10, 2020
Author(s)
Pengcheng Huo, Cheng Zhang, Wenqi Zhu, Mingze Liu, Song Zhang, Si Zhang, Lu Chen, Henri Lezec, Amit Agrawal, Yanqing Lu, Ting Xu
As the two most representative operation modes in an optical imaging system, bright-field imaging and phase contrast imaging can address different dimensionalities of an object. Developing a miniature and low-cost system capable of switching between these

Ultra-compact visible light depolarizer based on dielectric metasurface

February 4, 2020
Author(s)
Yilin Wang, Wenqi Zhu, Cheng Zhang, Qingbin Fan, Lu Chen, Henri Lezec, Amit Agrawal, Ting Xu
With rapid development towards shrinking the size of traditional photonic systems such as cameras, spectrometers, displays and illumination systems, there is an urgent need for high performance and ultra-compact functional optical elements. The large

Microscopic origin of the chiroptical response of optical media

October 11, 2019
Author(s)
Matthew S. Davis, Wenqi Zhu, Jay K. Lee, Henri Lezec, Amit Agrawal
The potential for enhancing the optical activity of natural chiral media using engineered nanophotonic components has been central in the quest towards developing next-generation circular-dichroism spectroscopic techniques. Through confinement and

Ultrathin Wetting Layer-Free Plasmonic Gold Films

October 3, 2019
Author(s)
Robert Lemasters, Cheng Zhang, Manoj Manjare, Wenqi Zhu, Junyeob Song, Sergei Urazhdin, Henri Lezec, Amit Agrawal, Hayk Harutyunyan
Ultrathin gold films are attractive for plasmonic and metamaterial devices, thanks to their useful optical and optoelectronic properties. However, deposition of ultrathin continuous Au films of few nanometer thickness is challenging and generally requires

Revisiting the Photon-Drag Effect in Metal Films

August 2, 2019
Author(s)
Jared H. Strait, Glenn E. Holland, Wenqi Zhu, Cheng Zhang, Bojan R. Ilic, Amit K. Agrawal, Domenico Pacifici, Henri J. Lezec
The photon-drag effect, the rectified current in a medium induced by conservation of momentum of absorbed or redirected light, is a unique probe of the detailed mechanisms underlying radiation pressure. We revisit this effect in gold, a canonical Drude

Ultrafast Optical Pulse Shaping using Dielectric Metasurfaces

May 2, 2019
Author(s)
Shawn M. Divitt, Wenqi Zhu, Cheng Zhang, Henri Lezec, Amit Agrawal
Simultaneous control of individual frequency-comb lines, and their modulation at the repetition-rate of an ultrafast laser represents the ultimate limit of optical pulse shaping. Remarkable progress in mode-locked lasers and chirped pulse amplifiers

Broadband generation of photonic spin-controlled arbitrary accelerating light beams in the visible

February 13, 2019
Author(s)
Qingbin Fan, Wenqi Zhu, Yuzhang Liang, Pengcheng Huo, Cheng Zhang, Amit Agrawal, Kun Huang, Xiangang Luo, Yanqing Lu, Chengwei Qiu, Henri Lezec, Ting Xu
Bending light along arbitrary curvatures is a captivating and popular notion, triggering unprecedented endeavors in achieving quasi-diffraction-free propagation along a curved path in free-space. Much effort has been devoted to achieving this goal in

Robust Extraction of Hyperbolic Metamaterial Permittivity using Total Internal Reflection Ellipsometry

June 20, 2018
Author(s)
Cheng Zhang, Nina Hong, Chengang Ji, Wenqi Zhu, Xi Chen, Amit K. Agrawal, Zhong Zhang, Tom E. Tiwald, Stefan Schoeche, James N. Hilfiker, L. Jay Guo, Henri J. Lezec
Hyperbolic metamaterials are optical materials characterized by highly anisotropic effective permittivity tensor components having opposite signs along orthogonal directions. The techniques currently employed for characterizing the optical properties of

Surface plasmon polariton laser based on a metallic trench Fabry-Perot resonator

October 6, 2017
Author(s)
Wenqi Zhu, Ting Xu, Haozhu Wang, Cheng Zhang, Parag B. Deotare, Amit K. Agrawal, Henri J. Lezec
Recent years have witnessed growing interest in the development of lasers with small footprint for their potential applications in small-volume sensing and on-chip optical communications. Surface-plasmons – electromagnetic modes evanescently confined to

Fabrication of Scanning Electrochemical Microscopy-Atomic Force Microscopy (SECM-AFM) Probes to Image Surface Topography and Reactivity at the Nanoscale

January 27, 2017
Author(s)
Jeyavel Velmurugan, Amit K. Agrawal, Sang M. An, Eric A. Choudhary, Veronika A. Szalai
Electrocatalysts, used in energy applications, rely on the solid-liquid interface to carry out productive chemistry. This interface is generally less amenable to standard surface-science characterization methods, making the investigation of the surface

Origins and Demonstrations of Electrons with Orbital Angular Momentum

January 9, 2017
Author(s)
Benjamin McMorran, Amit Agrawal, Peter Ercius, Vincenzo Grillo, Andrew Herzing, Tyler R. Harvey, Martin Linck
The surprising message of the 1992 paper of Allen, Beijersbergen, Spreeuw, and Woerdman (ABSW) was that photons could exhibit orbital motion in free space, which subsequently launched advancements in optical manipulation, microscopy, quantum optics

Steady State Vapor Bubble in Pool Boiling

February 3, 2016
Author(s)
An Zou, Ashish Chanana, Amit Agrawal, Peter C. Wayner, Jr., Shalabh C. Maroo
Boiling, a dynamic and multiscale process, has been studied for over five decades; however, a comprehensive understanding of the process is still lacking. The bubble ebullition cycle, which involves nucleation, growth and departure, happens over a very

High-contrast and fast electrochromic switching enabled by plasmonics

January 27, 2016
Author(s)
Ting Xu, Erich C. Walter, Amit Agrawal, Christopher C. Bohn, Jeyavel Velmurugan, Wenqi Zhu, Henri Lezec, Albert A. Talin
With vibrant colours and simple, room-temperature processing methods, electrochromic polymers have attracted attention as active materials for flexible, low-power-consuming devices. However, slow switching speeds in devices realized to date, as well as the

Efficient diffractive phase optics for electrons

September 1, 2014
Author(s)
Tyler R. Harvey, Jordan S. Pierce, Amit Agrawal, Benjamin McMorran, Peter Ercius, Martin Linck
Electron diffraction gratings can be used to imprint well-defined phase structure onto an electron beam. For example, diffraction gratings have been used to prepare electron beams with unique phase dislocations, such as electron vortex beams, which hold

Design Considerations for Enhancing Absorption in Semiconductors on Metals with Surface Plasmon Polaritons

March 5, 2014
Author(s)
Christopher C. Bohn, Amit K. Agrawal, Youngmin Lee, Charles J. Choi, Matthew Davis, Paul M. Haney, Henri J. Lezec, Veronika A. Szalai
Surface plasmon polaritons have attracted attention for energy applications such as photovoltaic and photoelectrochemical cells because of their ability to improve optical absorption in thin fi lms. We show that surface plasmon polaritons enhance

All-angle negative refraction and active flat lensing of ultraviolet light

May 22, 2013
Author(s)
Ting Xu, Amit Agrawal, Maxim Abashin, Kenneth J. Chau, Henri Lezec
The ability of a left-handed medium to sustain backwards electromagnetic waves leads to counter-intuitive phenomena such as negative refraction. We report the experimental implementation of a three-dimensional negative-index metamaterial operating at an

Effect of Tin Doping on alpha-Fe2O3 Photoanodes for Water Splitting

June 28, 2012
Author(s)
Christopher C. Bohn, Amit Agrawal, Erich C. Walter, Mark D. Vaudin, Andrew Herzing, Paul M. Haney, Albert A. Talin, Veronika Szalai
Sputtered-deposited films of α-Fe2O3 of thickness 600 nm were investigated as photoanodes for solar water splitting and found to have photocurrents as high as 0.8 mA/cm2 at 1.23 V vs. the reversible hydrogen electrode (RHE). The incorporation of Sn into

An Efficient Large-Area Grating Coupler for Surface Plasmon Polaritons

June 1, 2012
Author(s)
Stefan T. Koev, Amit K. Agrawal, Henri J. Lezec, Vladimir A. Aksyuk
We report the design, fabrication and characterization of a periodic grating of shallow rectangular grooves in a metallic film with the goal of maximizing the coupling efficiency of an extended plane wave (PW) of visible or near-IR frequency light into a