Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Carlos O. Aspetti is active.

Publication


Featured researches published by Carlos O. Aspetti.


Nature Materials | 2011

Tailoring hot-exciton emission and lifetimes in semiconducting nanowires via whispering-gallery nanocavity plasmons

Chang-Hee Cho; Carlos O. Aspetti; Michael E. Turk; James M. Kikkawa; Sung-Wook Nam; Ritesh Agarwal

The manipulation of radiative properties of light emitters coupled with surface plasmons is important for engineering new nanoscale optoelectronic devices, including lasers, detectors and single photon emitters. However, so far the radiative rates of excited states in semiconductors and molecular systems have been enhanced only moderately, typically by a factor of 10-50, producing emission mostly from thermalized excitons. Here, we show the generation of dominant hot-exciton emission, that is, luminescence from non-thermalized excitons that are enhanced by the highly concentrated electromagnetic fields supported by the resonant whispering-gallery plasmonic nanocavities of CdS-SiO(2)-Ag core-shell nanowire devices. By tuning the plasmonic cavity size to match the whispering-gallery resonances, an almost complete transition from thermalized exciton to hot-exciton emission can be achieved, which reflects exceptionally high radiative rate enhancement of >10(3) and sub-picosecond lifetimes. Core-shell plasmonic nanowires are an ideal test bed for studying and controlling strong plasmon-exciton interaction at the nanoscale and opens new avenues for applications in ultrafast nanophotonic devices.


Nature Photonics | 2013

Silicon coupled with plasmon nanocavities generates bright visible hot luminescence

Chang-Hee Cho; Carlos O. Aspetti; Joohee Park; Ritesh Agarwal

Due to limitations in device speed and performance of silicon-based electronics, silicon optoelectronics has been extensively studied to achieve ultrafast optical-data processing1–3. However, the biggest challenge has been to develop an efficient silicon-based light source since indirect band-gap of silicon gives rise to extremely low emission efficiency. Although light emission in quantum-confined silicon at sub-10 nm lengthscales has been demonstrated4–7, there are difficulties in integrating quantum structures with conventional electronics8,9. It is desirable to develop new concepts to obtain emission from silicon at lengthscales compatible with current electronic devices (20-100 nm), which therefore do not utilize quantum-confinement effects. Here, we demonstrate an entirely new method to achieve bright visible light emission in “bulk-sized” silicon coupled with plasmon nanocavities from non-thermalized carrier recombination. Highly enhanced emission quantum efficiency (>1%) in plasmonic silicon, along with its size compatibility with present silicon electronics, provides new avenues for developing monolithically integrated light-sources on conventional microchips.


Reports on Progress in Physics | 2014

Tailoring light–matter coupling in semiconductor and hybrid-plasmonic nanowires

Brian Piccione; Carlos O. Aspetti; Chang-Hee Cho; Ritesh Agarwal

Understanding interactions between light and matter is central to many fields, providing invaluable insights into the nature of matter. In its own right, a greater understanding of light-matter coupling has allowed for the creation of tailored applications, resulting in a variety of devices such as lasers, switches, sensors, modulators, and detectors. Reduction of optical mode volume is crucial to enhancing light-matter coupling strength, and among solid-state systems, self-assembled semiconductor and hybrid-plasmonic nanowires are amenable to creation of highly-confined optical modes. Following development of unique spectroscopic techniques designed for the nanowire morphology, carefully engineered semiconductor nanowire cavities have recently been tailored to enhance light-matter coupling strength in a manner previously seen in optical microcavities. Much smaller mode volumes in tailored hybrid-plasmonic nanowires have recently allowed for similar breakthroughs, resulting in sub-picosecond excited-state lifetimes and exceptionally high radiative rate enhancement. Here, we review literature on light-matter interactions in semiconductor and hybrid-plasmonic monolithic nanowire optical cavities to highlight recent progress made in tailoring light-matter coupling strengths. Beginning with a discussion of relevant concepts from optical physics, we will discuss how our knowledge of light-matter coupling has evolved with our ability to produce ever-shrinking optical mode volumes, shifting focus from bulk materials to optical microcavities, before moving on to recent results obtained from semiconducting nanowires.


Nature Communications | 2014

Enhanced second-harmonic generation from metal-integrated semiconductor nanowires via highly confined whispering gallery modes

Ming-Liang Ren; Wenjing Liu; Carlos O. Aspetti; Liaoxin Sun; Ritesh Agarwal

Coherent and tunable nanoscale light sources utilizing optical nonlinearities are required for applications ranging from imaging and bio-sensing to on-chip all-optical signal processing. However, owing to their small sizes, the efficiency of nanostructures even with high nonlinear coefficients is poor, therefore requiring very high excitation energies. Although surface-plasmon resonances of metal nanostructures can enhance surface nonlinear processes such as second-harmonic generation, they still suffer from low conversion efficiencies owing to their intrinsically low nonlinear coefficients. Here we show highly enhanced and directional second-harmonic generation from individual CdS nanowires integrated with silver nanocavities (>1,000 times higher external efficiency compared with bare CdS), in which the lowest-order whispering gallery mode is engineered to concentrate light in the nonlinear material while minimizing Ohmic losses. The directional nonlinear signal is redirected into another waveguide, which is then utilized to configure an optical router that can potentially serve as a tunable coherent light source to enable on-chip signal processing for integrated nanophotonic systems.


Journal of Physical Chemistry A | 2011

Variable Temperature Spectroscopy of As-Grown and Passivated CdS Nanowire Optical Waveguide Cavities

Lambert K. van Vugt; Brian Piccione; Chang-Hee Cho; Carlos O. Aspetti; Aaron D. Wirshba; Ritesh Agarwal

Semiconductor nanowire waveguide cavities hold promise for nanophotonic applications such as lasers, waveguides, switches, and sensors due to the tight optical confinement in these structures. However, to realize their full potential, high quality nanowires, whose emission at low temperatures is dominated by free exciton emission, need to be synthesized. In addition, a proper understanding of their complex optical properties, including light-matter coupling in these subwavelength structures, is required. We have synthesized very high-quality wurztite CdS nanowires capped with a 5 nm SiO(2) conformal coating with diameters spanning 100-300 nm using physical vapor and atomic layer deposition techniques and characterized their spatially resolved photoluminescence over the 77-298 K temperature range. In addition to the Fabry-Pérot resonator modulated emission from the ends of the wires, the low temperature emission from the center of the wire shows clear free excitonic peaks and LO phonon replicas, persisting up to room-temperature in the passivated wires. From laser scanning measurements we determined the absorption in the vicinity of the excitonic resonances. In addition to demonstrating the high optical quality of the nanowire crystals, these results provide the fundamental parameters for strong light-matter coupling studies, potentially leading to low threshold polariton lasers, sensitive sensors and optical switches at the nanoscale.


Nano Letters | 2017

Engineering Localized Surface Plasmon Interactions in Gold by Silicon Nanowire for Enhanced Heating and Photocatalysis

Daksh Agarwal; Carlos O. Aspetti; Matteo Cargnello; Ming-Liang Ren; Jinkyoung Yoo; Christopher B. Murray; Ritesh Agarwal

The field of plasmonics has attracted considerable attention in recent years because of potential applications in various fields such as nanophotonics, photovoltaics, energy conversion, catalysis, and therapeutics. It is becoming increasing clear that intrinsic high losses associated with plasmons can be utilized to create new device concepts to harvest the generated heat. It is therefore important to design cavities, which can harvest optical excitations efficiently to generate heat. We report a highly engineered nanowire cavity, which utilizes a high dielectric silicon core with a thin plasmonic film (Au) to create an effective metallic cavity to strongly confine light, which when coupled with localized surface plasmons in the nanoparticles of the thin metal film produces exceptionally high temperatures upon laser irradiation. Raman spectroscopy of the silicon core enables precise measurements of the cavity temperature, which can reach values as high as 1000 K. The same Si-Au cavity with enhanced plasmonic activity when coupled with TiO2 nanorods increases the hydrogen production rate by ∼40% compared to similar Au-TiO2 system without Si core, in ethanol photoreforming reactions. These highly engineered thermoplasmonic devices, which integrate three different cavity concepts (high refractive index core, metallo-dielectric cavity, and localized surface plasmons) along with the ease of fabrication demonstrate a possible pathway for designing optimized plasmonic devices with applications in energy conversion and catalysis.


Journal of Physical Chemistry Letters | 2014

Tailoring the Spectroscopic Properties of Semiconductor Nanowires via Surface-Plasmon-Based Optical Engineering

Carlos O. Aspetti; Ritesh Agarwal

Semiconductor nanowires, due to their unique electronic, optical, and chemical properties, are firmly placed at the forefront of nanotechnology research. The rich physics of semiconductor nanowire optics arises due to the enhanced light–matter interactions at the nanoscale and coupling of optical modes to electronic resonances. Furthermore, confinement of light can be taken to new extremes via coupling to the surface plasmon modes of metal nanostructures integrated with nanowires, leading to interesting physical phenomena. This Perspective will examine how the optical properties of semiconductor nanowires can be altered via their integration with highly confined plasmonic nanocavities that have resulted in properties such as orders of magnitude faster and more efficient light emission and lasing. The use of plasmonic nanocavities for tailored optical absorption will also be discussed in order to understand and engineer fundamental optical properties of these hybrid systems along with their potential for novel applications, which may not be possible with purely dielectric cavities.


Nano Letters | 2014

Studies of Hot Photoluminescence in Plasmonically Coupled Silicon via Variable Energy Excitation and Temperature-Dependent Spectroscopy

Carlos O. Aspetti; Chang-Hee Cho; Rahul Agarwal; Ritesh Agarwal

By integrating silicon nanowires (∼150 nm diameter, 20 μm length) with an Ω-shaped plasmonic nanocavity, we are able to generate broadband visible luminescence, which is induced by high order hybrid nanocavity-surface plasmon modes. The nature of this super bandgap emission is explored via photoluminescence spectroscopy studies performed with variable laser excitation energies (1.959 to 2.708 eV) and finite difference time domain simulations. Furthermore, temperature-dependent photoluminescence spectroscopy shows that the observed emission corresponds to radiative recombination of unthermalized (hot) carriers as opposed to a resonant Raman process.


international workshop on computational electronics | 2014

Plasmon excitation of coherent interface phonons in Si-SiO 2 systems

Min S. Choi; Nanzhu Zhang; Mitra Dutta; Michael A. Stroscio; Carlos O. Aspetti; Ritesh Agarwal

Coherent interface phonon generation by surface plasmon in silver-SiO2-silicon system is analyzed, based on the impulsive stimulated scattering theory model. The surface plasmon is first analyzed, and applied to semiclassical stimulated Raman scattering theory. Our calculatation shows that the photon-induced surface plasmons store about 20-30% of the total incoming energy, and it is considered in the analysis. Phonon potential of the generated phonons is also calculated.


Archive | 2012

EMISSION IN NANOSCALE STRUCTURES VIA NANOCAVITY PLASMONS

Ritesh Agarwal; Chang-Hee Cho; Carlos O. Aspetti

Collaboration


Dive into the Carlos O. Aspetti's collaboration.

Top Co-Authors

Avatar

Ritesh Agarwal

University of Pennsylvania

View shared research outputs
Top Co-Authors

Avatar

Chang-Hee Cho

Daegu Gyeongbuk Institute of Science and Technology

View shared research outputs
Top Co-Authors

Avatar

Brian Piccione

University of Pennsylvania

View shared research outputs
Top Co-Authors

Avatar

Ming-Liang Ren

University of Pennsylvania

View shared research outputs
Top Co-Authors

Avatar

James M. Kikkawa

University of Pennsylvania

View shared research outputs
Top Co-Authors

Avatar

Jinkyoung Yoo

Los Alamos National Laboratory

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Liaoxin Sun

University of Pennsylvania

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Michael A. Stroscio

University of Illinois at Chicago

View shared research outputs
Researchain Logo
Decentralizing Knowledge