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Dive into the research topics where Mauro Melli is active.

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Featured researches published by Mauro Melli.


Advanced Materials | 2015

Revealing Optical Properties of Reduced-Dimensionality Materials at Relevant Length Scales.

Ogletree Df; Schuck Pj; Alexander Weber-Bargioni; Nicholas J. Borys; Shaul Aloni; Wei Bao; Barja S; Jiye Lee; Mauro Melli; Keiko Munechika; Stephen Whitelam; Sebastian Wickenburg

Reduced-dimensionality materials for photonic and optoelectronic applications including energy conversion, solid-state lighting, sensing, and information technology are undergoing rapid development. The search for novel materials based on reduced-dimensionality is driven by new physics. Understanding and optimizing material properties requires characterization at the relevant length scale, which is often below the diffraction limit. Three important material systems are chosen for review here, all of which are under investigation at the Molecular Foundry, to illustrate the current state of the art in nanoscale optical characterization: 2D semiconducting transition metal dichalcogenides; 1D semiconducting nanowires; and energy-transfer in assemblies of 0D semiconducting nanocrystals. For each system, the key optical properties, the principal experimental techniques, and important recent results are discussed. Applications and new developments in near-field optical microscopy and spectroscopy, scanning probe microscopy, and cathodoluminescence in the electron microscope are given detailed attention. Work done at the Molecular Foundry is placed in context within the fields under review. A discussion of emerging opportunities and directions for the future closes the review.


Scientific Reports | 2017

Optical metasurfaces for high angle steering at visible wavelengths

Dianmin Lin; Mauro Melli; Evgeni Poliakov; Pierre St. Hilaire; Scott Dhuey; Christophe Peroz; Stefano Cabrini; Mark L. Brongersma; Michael Anthony Klug

Metasurfaces have facilitated the replacement of conventional optical elements with ultrathin and planar photonic structures. Previous designs of metasurfaces were limited to small deflection angles and small ranges of the angle of incidence. Here, we have created two types of Si-based metasurfaces to steer visible light to a large deflection angle. These structures exhibit high diffraction efficiencies over a broad range of angles of incidence. We have demonstrated metasurfaces working both in transmission and reflection modes based on conventional thin film silicon processes that are suitable for the large-scale fabrication of high-performance devices.


Scientific Reports | 2017

Campanile Near-Field Probes Fabricated by Nanoimprint Lithography on the Facet of an Optical Fiber

Giuseppe Carlo Calafiore; Alexander Koshelev; Thomas P. Darlington; Nicholas J. Borys; Mauro Melli; Aleksandr Polyakov; Giuseppe Cantarella; Frances I. Allen; Paul Lum; Ed Wong; Simone Sassolini; Alexander Weber-Bargioni; P. James Schuck; Stefano Cabrini; Keiko Munechika

One of the major challenges to the widespread adoption of plasmonic and nano-optical devices in real-life applications is the difficulty to mass-fabricate nano-optical antennas in parallel and reproducible fashion, and the capability to precisely place nanoantennas into devices with nanometer-scale precision. In this study, we present a solution to this challenge using the state-of-the-art ultraviolet nanoimprint lithography (UV-NIL) to fabricate functional optical transformers onto the core of an optical fiber in a single step, mimicking the ‘campanile’ near-field probes. Imprinted probes were fabricated using a custom-built imprinter tool with co-axial alignment capability with sub <100 nm position accuracy, followed by a metallization step. Scanning electron micrographs confirm high imprint fidelity and precision with a thin residual layer to facilitate efficient optical coupling between the fiber and the imprinted optical transformer. The imprinted optical transformer probe was used in an actual NSOM measurement performing hyperspectral photoluminescence mapping of standard fluorescent beads. The calibration scans confirmed that imprinted probes enable sub-diffraction limited imaging with a spatial resolution consistent with the gap size. This novel nano-fabrication approach promises a low-cost, high-throughput, and reproducible manufacturing of advanced nano-optical devices.


Nanoscale | 2015

Gain and Raman line-broadening with graphene coated diamond-shape nano-antennas

Charilaos Paraskevaidis; Tevye Kuykendall; Mauro Melli; Alexander Weber-Bargioni; P. James Schuck; Adam M. Schwartzberg; Scott Dhuey; Stefano Cabrini; Haim Grebel

Using Surface Enhanced Raman Scattering (SERS), we report on intensity-dependent broadening in graphene-deposited broad-band antennas. The antenna gain curve includes both the incident frequency and some of the scattered mode frequencies. By comparing antennas with various gaps and types (bow-tie vs. diamond-shape antennas) we make the case that the line broadening did not originate from strain, thermal or surface potential. Strain, if present, further shifts and broadens those Raman lines that are included within the antenna gain curve.


Proceedings of SPIE | 2015

Manipulating the spatial extent of the exciton diffusion through QDs assembly by controlling dimensionality, energy landscape, and exciton density (Presentation Recording)

Keiko Munechika; Jiye Lee; Dimitrios Simatos; Mauro Melli; Steve Whitelam; Alexander Weber-Bargioni

Semiconductor quantum dots are considered a promising material class with the potential of highly tunable and novel optoelectronic properties. Recent research efforts have shown that quantum dots, assembled in well-ordered 1D, 2D and 3D geometries have the potential to funnel excitons via Forster Resonance Energy Transfer (FRET) through the nanocrystal composite. Understanding the inter quantum dot coupling and the spatial extend of exciton diffusion is key to design material for the deliberate control of energy transport through them. In this regard, we study Förster Resonance Energy Transfer (FRET) between CdSe quantum dots in a well-defined 2D assembly with different interparticle distances. We then examine the spatial extent of FRET coupling between quantum dots using confocal fluorescence hyperspectral imaging. We spatially map out the degree of the coupling between the neighboring quantum dots by exciting the quantum dots at a known location and collect fluorescence signals at various distances relative to the excitation. We show that by varying the dimensionality, energy landscape, and exciton density, we are able to manipulate the spatial extent of exciton diffusion through the QDs assembly. Modeling was done in conjunction the experiments and well described our observations in each case. The results provide in-depth understanding into the spatial extent of exciton diffusion via FRET through ordered quantum dot assemblies and provide useful insights in engineering nano-building structures to direct and enhance the direction of the exciton transport to a preferred sites.


Advanced Materials | 2015

Near‐Field Imaging: Revealing Optical Properties of Reduced‐Dimensionality Materials at Relevant Length Scales (Adv. Mater. 38/2015)

D. Frank Ogletree; P. James Schuck; Alexander Weber-Bargioni; Nicholas J. Borys; Shaul Aloni; Wei Bao; Sara Barja; Jiye Lee; Mauro Melli; Keiko Munechika; Stephan Whitelam; Sebastian Wickenburg

Optimizing the optical properties of reduced-dimensionality materials requires characterization at the relevant length scale, often below the diffraction limit. On page 5693, D. F. Ogletree and co-workers review the current state of the art for 0D, 1D, and 2D nanomaterials, including novel techniques like the Molecular Foundrys Campanile probe.


Nature Energy | 2016

Facet-dependent photovoltaic efficiency variations in single grains of hybrid halide perovskite

Sibel Y. Leblebici; Linn Leppert; Yanbo Li; Sebastian E. Reyes-Lillo; Sebastian Wickenburg; Ed Wong; Jiye Lee; Mauro Melli; Dominik Ziegler; Daniel K. Angell; D. Frank Ogletree; Paul D. Ashby; Francesca M. Toma; Jeffrey B. Neaton; Ian D. Sharp; Alexander Weber-Bargioni


Physical review applied | 2017

Near-Field Imaging of Free Carriers in ZnO Nanowires with a Scanning Probe Tip Made of Heavily Doped Germanium

Emilie Sakat; Valeria Giliberti; Monica Bollani; A. Notargiacomo; Marialilia Pea; Marco Finazzi; Giovanni Pellegrini; Jean-Paul Hugonin; Alexander Weber-Bargioni; Mauro Melli; Simone Sassolini; Stefano Cabrini; Paolo Biagioni; M. Ortolani; L. Baldassarre


Light-Science & Applications | 2014

Coupling model for an extended-range plasmonic optical transformer scanning probe

Aleksandr Polyakov; Mauro Melli; Giuseppe Cantarella; Adam M. Schwartzberg; Alexander Weber-Bargioni; P. James Schuck; Stefano Cabrini


Archive | 2017

METASURFACES FOR REDIRECTING LIGHT AND METHODS FOR FABRICATING

Dianmin Lin; Mauro Melli; Pierre St. Hilaire; Christophe Peroz; Evgeni Poliakov

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Stefano Cabrini

Lawrence Berkeley National Laboratory

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P. James Schuck

Lawrence Berkeley National Laboratory

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M. Ortolani

Sapienza University of Rome

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Valeria Giliberti

Istituto Italiano di Tecnologia

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Christophe Peroz

Lawrence Berkeley National Laboratory

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Scott Dhuey

Lawrence Berkeley National Laboratory

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Leonetta Baldassarre

Istituto Italiano di Tecnologia

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Monica Bollani

National Research Council

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