Felipe Antolinez

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Antolinez

First Name

Felipe

ORCID

0000-0002-1787-0112

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Publications 1 - 10 of 10

Defect-Tolerant Plasmonic Elliptical Resonators for Long-Range Energy Transfer
Antolinez, Felipe; Winkler, Jan M.; Rohner, Patrik; et al. (2019)
ACS Nano
Controllable Formation of Nanofilaments in Resistive Memories via Tip-Enhanced Electric Fields
Shin, Keun-Young; Kim, Youngjin; Antolinez, Felipe; et al. (2016)
Advanced Electronic Materials
Low-Temperature Emission Behavior of CdSe-Based Nanoplatelets
Antolinez, Felipe (2019)
Colloidal nanoplatelets (NPLs) are atomically flat, quasi-two-dimensional sheets of semiconductor with a well-defined thickness. The possibility to precisely control their thickness allows extremely narrow spectral absorption and emission linewidths. However, despite seemingly simple optical properties at room temperature, the low-temperature emission of NPLs reveals much more complex photophysics. Here, we investigate the emission of CdSe NPLs using calculations and optical spectroscopy at cryogenic temperatures. In addition, we show how an elliptical Ag resonator can enhance energy transfer between distant semiconductor nanocrystals through surface plasmon polaritons (SPPs). First, we use an effective-mass model to calculate exciton states in laterally confined NPLs. The exciton binding energy is strongly enhanced by the dielectric effect and thus depends on the permittivity of the surrounding medium. To investigate the effect of surface inhomogeneities on the optical properties of NPLs, we consider the potential generated by a positive charge at the NPL surface. We find that this inhomogeneity localizes the exciton wave function and lowers the exciton energy by ~30 meV. This finding indicates the emergence of quantum-dot-like emission behavior in two-dimensional NPLs, which could significantly increase nonradiative Auger relaxation in NPLs with surface inhomogeneities. Moreover, the exciton localization considerably reduces the transition oscillator strength compared to NPLs with perfectly homogeneous surfaces. Second, we study the time- and temperature-dependent photoluminescence (PL) of core CdSe NPLs. At temperatures below ~160 K, we observe two closely-spaced emission features in their PL spectrum. In contrast to spherical quantum dots (QDs), nonradiative trion Auger recombination is strongly suppressed in NPLs as the charge carriers are only weakly confined in the lateral dimensions. Therefore, we assign the low-energy PL peak to radiative trion emission from charged NPLs. Because photoinduced defects facilitate nonradiative Auger recombination, photodarkening affects trion emission more strongly than exciton emission. Temperature-dependent intensity measurements of the two emission peaks further confirm our interpretation of suppressed nonradiative Auger recombination of trions at low temperatures. Our finding has implications on the low-temperature emission behavior for potentially a wider range of nanocrystals that are in the weak-confinement limit. Third, we investigate the origin of the broad and asymmetric ensemble emission spectrum of CdSe/CdS core/shell heterostructure NPLs. Using single-particle spectroscopy at cryogenic temperature, we observe an unexpectedly complex series of narrow peaks in their emission spectra. Moreover, and seemingly uncorrelated with the total emission intensity, these spectra change dramatically every few seconds. To analyze large numbers of emission spectra efficiently, we apply machine-learning algorithms that allow for the reconstruction of high signal-to-noise spectra for different emission states. Based on the simultaneous analysis of the decay dynamics, we attribute the observed peaks to emission from a negatively charged exciton (trion), together with shakeup replica. In our NPLs, these shakeup lines are observable due to the discrete states of the resident electron that originate from weak lateral quantum confinement. Fourth, we fabricate plasmonic elliptical resonators to achieve long-distance energy transfer mediated by SPPs. In an ellipse, all SPPs launched at one focal point propagate to the other focal point after one reflection independent of the path. To confirm this property for our structures, we measure the transmission spectrum from focal point to focal point with a white-light laser. Our measurements reveal closely spaced resonator modes with quality factors of ~100. By electrohydrodynamic nano-drip printing, we precisely print green donor and red acceptor QDs at the two ellipse focal points. We then selectively excite the donor QDs with a focused laser and use time- and spectrally resolved measurements to show plasmon-mediated energy transfer across 10 µm. Importantly, our elliptical resonators sustain energy transfer between the focal points even if large defects block the direct path between the donor and acceptor. In summary, this thesis investigates the emission properties of colloidal NPLs via optical spectroscopy at cryogenic temperatures and shows how nanocrystals can be coupled through surface plasmons.
Microsecond Blinking Events in the Fluorescence of Colloidal Quantum Dots Revealed by Correlation Analysis on Preselected Photons
Rabouw, Freddy T.; Antolinez, Felipe; Brechbühler, Raphael; et al. (2019)
The Journal of Physical Chemistry Letters
Nearly all colloidal quantum dots, when measured at the single-emitter level, exhibit fluorescence “blinking”. However, despite over 20 years of research on this phenomenon, its microscopic origins are still debated. One reason is a gap in available experimental information, specifically for dynamics at short (submillisecond) time scales. Here, we use photon-correlation analysis to investigate microsecond blinking events in individual quantum dots. While the strongly distributed kinetics of blinking normally makes such events difficult to study, we show that they can be analyzed by excluding photons emitted during long bright or dark periods. Moreover, we find that submillisecond blinking events are more common than one might expect from extrapolating the power-law blinking statistics observed on longer (millisecond) time scales. This result provides important experimental data for developing a microscopic understanding of blinking. More generally, our method offers a simple strategy for analyzing microsecond switching dynamics in the fluorescence of quantum emitters.
A customizable class of colloidal-quantum-dot spasers and plasmonic amplifiers
Kress, Stephan J.P.; Cui, Jian; Rohner, Patrik; et al. (2017)
Science Advances
Colloidal quantum dots are robust, efficient, and tunable emitters now used in lighting, displays, and lasers. Consequently, when the spaser—a laser-like source of high-intensity, narrow-band surface plasmons—was first proposed, quantum dots were specified as the ideal plasmonic gain medium for overcoming the significant intrinsic losses of plasmons. Many subsequent spasers, however, have required a single material to simultaneously provide gain and define the plasmonic cavity, a design unable to accommodate quantum dots and other colloidal nanomaterials. In addition, these and other designs have been ill suited for integration with other elements in a larger plasmonic circuit, limiting their use. We develop a more open architecture that decouples the gain medium from the cavity, leading to a versatile class of quantum dot–based spasers that allow controlled generation, extraction, and manipulation of plasmons. We first create aberration-corrected plasmonic cavities with high quality factors at desired locations on an ultrasmooth silver substrate. We then incorporate quantum dots into These cavities via electrohydrodynamic printing or drop-casting. Photoexcitation under ambient conditions generates monochromatic plasmons (0.65-nm linewidth at 630 nm, Q ~ 1000) above threshold. This signal is extracted, directed through an integrated amplifier, and focused at a nearby nanoscale tip, generating intense electromagnetic fields. More generally, our device platform can be straightforwardly deployed at different wavelengths, size scales, and geometries on large-area plasmonic chips for fundamental studies and applications.
Role of Gain in Fabry−Pérot Surface Plasmon Polariton Lasers
Aellen, Marianne; Rossinelli, Aurelio; Keitel, Robert; et al. (2022)
ACS Photonics
Plasmonic lasers generate strongly confined electromagnetic fields over a narrow range of wavelengths. This is potentially useful for enhancing nonlinear effects, sensing chemical species, and providing on-chip sources of plasmons. By placing a semiconductor gain layer near a metallic interface with a gap layer in between, plasmonic lasers have been demonstrated. However, the role of gain in this common design has been understudied, leading to suboptimal choices. Here, we examine planar metallic lasers and explore the effect of gain on the lasing behavior. We print semiconductor nanoplatelets as a gain layer of controllable thickness onto alumina-coated silver films with integrated planar Fabry–Pérot cavities. Lasing behavior is then monitored with spectrally and polarization-resolved far-field imaging. The results are compared with a theoretical waveguide model and a rate-equation model, which consider both plasmonic and photonic modes and explicitly include losses and gain. We find that the nature of the lasing mode is dictated by the gain-layer thickness and, contrary to conventional wisdom, a gap layer with a high refractive index can be advantageous for plasmonic lasing in planar Fabry–Pérot cavities. Our rate-equation model also reveals a regime where plasmonic and photonic modes compete in an unintuitive way, potentially useful for facile, active mode switching. These results can guide future design of metallic lasers and could lead to on-chip lasers with controlled photonic and plasmonic output.
High-temperature growth of thick-shell CdSe/CdS core/shell nanoplatelets
Rossinelli, Aurelio; Riedinger, Andreas; Marqués-Gallego, Patricia; et al. (2017)
Chemical Communications
Wedge Waveguides and Resonators for Quantum Plasmonics
Kress, Stephan J.P.; Antolinez, Felipe; Richner, Patrizia; et al. (2015)
Nano Letters
Plasmonic structures can provide deep-subwavelength electromagnetic fields that are useful for enhancing light–matter interactions. However, because these localized modes are also dissipative, structures that offer the best compromise between field confinement and loss have been sought. Metallic wedge waveguides were initially identified as an ideal candidate but have been largely abandoned because to date their experimental performance has been limited. We combine state-of-the-art metallic wedges with integrated reflectors and precisely placed colloidal quantum dots (down to the single-emitter level) and demonstrate quantum-plasmonic waveguides and resonators with performance approaching theoretical limits. By exploiting a nearly 10-fold improvement in wedge-plasmon propagation (19 μm at a vacuum wavelength, λvac, of 630 nm), efficient reflectors (93%), and effective coupling (estimated to be >70%) to highly emissive (∼90%) quantum dots, we obtain Ag plasmonic resonators at visible wavelengths with quality factors approaching 200 (3.3 nm line widths). As our structures offer modal volumes down to ∼0.004λvac3 in an exposed single-mode waveguide–resonator geometry, they provide advantages over both traditional photonic microcavities and localized-plasmonic resonators for enhancing light–matter interactions. Our results confirm the promise of wedges for creating plasmonic devices and for studying coherent quantum-plasmonic effects such as long-distance plasmon-mediated entanglement and strong plasmon–matter coupling.
Observation of Electron Shakeup in CdSe/CdS Core/Shell Nanoplatelets
Antolinez, Felipe; Rabouw, Freddy T.; Rossinelli, Aurelio; et al. (2019)
Nano Letters
Trion Emission Dominates the Low-Temperature Photoluminescence of CdSe Nanoplatelets
Antolinez, Felipe; Rabouw, Freddy T.; Rossinelli, Aurelio; et al. (2020)
Nano Letters
Colloidal nanoplatelets (NPLs) are atomically flat, quasi-two-dimensional particles of a semiconductor. Despite intense interest in their optical properties, several observations concerning the emission of CdSe NPLs remain puzzling. While their ensemble photoluminescence spectrum consists of a single narrow peak at room temperature, two distinct emission features appear at temperatures below ∼160 K. Several competing explanations for the origin of this two-color emission have been proposed. Here, we present temperature- and time-dependent experiments demonstrating that the two emission colors are due to two subpopulations of uncharged and charged NPLs. We study dilute films of isolated NPLs, thus excluding any explanation relying on collective effects due to NPL stacking. Temperature-dependent measurements explain that trion emission from charged NPLs is bright at cryogenic temperatures, while temperature activation of nonradiative Auger recombination quenches the trion emission above 160 K. Our findings clarify many of the questions surrounding the photoluminescence of CdSe NPLs.

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Felipe Antolinez

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