ACS Photonics

Journal: ACS Photonics

Publisher

American Chemical Society

ISSN

2330-4022

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Publications 1 - 10 of 92

Size, Ligand, and Defect-Dependent Electron-Phonon Coupling in Chalcogenide and Perovskite Nanocrystals and Its Impact on Luminescence Line Widths
Yazdani, Nuri; Volk, Sebastian; Yarema, Olesya; et al. (2020)
ACS Photonics
Discerning Amyloid-β and Tau Pathologies with Learning-Based Quantum Sensing
Sundar, Shruti; Jabir , Marakkarakath Vadakkepurayil; Glandorf, Lukas Benjamin; et al. (2025)
ACS Photonics
Photon entanglement, a key feature of quantum correlations, provides a level of coherence absent in classical correlations, potentially offering new information when interacting with biological matter. One promising application is using entanglement decoherence to distinguish between healthy and diseased samples. However, achieving this requires efficient entangled photon sources capable of surviving through biological samples for reliable detection. In this work, we show the applicability of a polarization-entangled photon source as a label-free diagnostic tool for distinguishing between transgenic mouse models of amyloidosis and tauopathy and their respective control strains. We investigated cortical and hippocampal regions of these models, and our findings revealed greater preservation of entanglement in the transgenic samples compared to controls. To further enhance classification accuracy, we employed a supervised machine learning approach, achieving reliable distinctions between disease and control groups in unseen test samples. The quantum-based results were further validated through confocal imaging of the transgenic and control samples. These findings suggest that quantum sensing could serve as a label-free approach for distinguishing biological samples, with potential applications in the study of neurodegenerative disorders.
Monolithic Integration of Mid-Infrared Quantum Cascade Lasers and Frequency Combs with Passive Waveguides
Wang, Ruijun; Täschler, Philipp; Wang, Zhixin; et al. (2022)
ACS Photonics
Mid-infrared semiconductor lasers in photonic integrated circuits are of considerable interest for a variety of industrial, environmental, and medical applications. However, photonic integration technologies in the mid-infrared lag far behind the near-infrared range. Here we present the monolithic integration of mid-infrared quantum cascade lasers with low-loss passive waveguides via butt-coupling. The passive waveguide losses are experimentally evaluated to be only 1.2 ± 0.3 dB/cm, with negligible butt-coupling losses. We demonstrate continuous-wave lasing at room temperature of these active-to-passive waveguide coupled devices. Moreover, we report a frequency comb operation paving the way toward on-chip, mid-infrared, dual-comb sensors.
Long-Range and Dead-Zone-Free Dual-Comb Ranging for the Interferometric Tracking of Moving Targets
Camenzind, Sandro L.; Lang, Lukas; Willenberg, Benjamin; et al. (2025)
ACS Photonics
Dual-comb ranging has emerged as an effective technology for long-distance metrology, providing absolute distance measurements with high speed, precision, and accuracy. Here, we demonstrate a dual-comb ranging method that utilizes a free-space transceiver unit, enabling dead-zone-free measurements and simultaneous ranging with interchanged comb roles to allow for long-distance measurements, even when the target is moving. It includes a graphics processing unit (GPU)-accelerated algorithm for real-time signal processing and a free-running single-cavity solid-state dual-comb laser with a carrier wavelength λ$_c$ ≈ 1055 nm, a pulse repetition rate of 1 GHz, and a repetition rate difference of 5.06 kHz. This combination offers a fast update rate and sufficient signal strength to reach a single-shot time-of-flight precision of around 0.1 mu m (i.e., <λ$_c$/4) on a cooperative target placed at a distance of more than 40 m. The free-running laser is sufficiently stable to use the phase information for interferometric distance measurements, which improves the single-shot precision to <20 nm. To assess the ranging accuracy, we track the motion of the cooperative target when moved over 40 m and compare it to a reference interferometer. The residuals between the two measurements are below 3 mu m. These results highlight the potential of this approach for accurate and dead-zone-free long-distance ranging, supporting real-time tracking with nm-level precision.
Optically Driven Janus Microengine with Full Orbital Motion Control
Bronte Ciriza, David; Callegari, Agnese; Donato, Maria Grazia; et al. (2023)
ACS Photonics
Microengines have shown promise for a variety of applications in nanotechnology, microfluidics, and nanomedicine, including targeted drug delivery, microscale pumping, and environmental remediation. However, achieving precise control over their dynamics remains a significant challenge. In this study, we introduce a microengine that exploits both optical and thermal effects to achieve a high degree of controllability. We find that in the presence of a strongly focused light beam, a gold-silica Janus particle becomes confined at the stationary point where the optical and thermal forces balance. By using circularly polarized light, we can transfer angular momentum to the particle, breaking the symmetry between the two forces and resulting in a tangential force that drives directed orbital motion. We can simultaneously control the velocity and direction of rotation of the particle changing the ellipticity of the incoming light beam while tuning the radius of the orbit with laser power. Our experimental results are validated using a geometrical optics phenomenological model that considers the optical force, the absorption of optical power, and the resulting heating of the particle. The demonstrated enhanced flexibility in the control of microengines opens up new possibilities for their utilization in a wide range of applications, including microscale transport, sensing, and actuation.
Bridging the “Last Millimeter” Gap of Brain-Machine Interfaces via Near-Infrared Wireless Power Transfer and Data Communications
Moon, Eunseong; Barrow, Michael; Lim, Jongyup; et al. (2021)
ACS Photonics
Arrays of floating neural sensors with a high channel count that covers an area of square centimeters and larger would be transformative for neural engineering and brain–machine interfaces. Meeting the power and wireless data communications requirements within the size constraints for each neural sensor has been elusive due to the need to incorporate sensing, computing, communications, and power functionality in a package of approximately 100 μm on a side. In this work, we demonstrate a near-infrared optical power and data communication link for a neural recording system that satisfies size requirements to achieve dense arrays and power requirements to prevent tissue heating. The optical link is demonstrated using an integrated optoelectronic device consisting of a tandem photovoltaic cell and microscale light-emitting diode. End-to-end functionality of a wireless neural link within system constraints is demonstrated using a prerecorded neural signal between a self-powered CMOS integrated circuit and single photon avalanche photodiode.
Transition Metal Dichalcogenide Resonators for Second Harmonic Signal Enhancement
Busschaert, Sebastian; Reimann, Rene; Cavigelli, Moritz; et al. (2020)
ACS Photonics
In addition to their strong nonlinear optical response, transition metal dichalcogenides (TMDCs) possess a high refractive index in the visible and infrared regime. Therefore, by patterning those TMDCs into dielectric nanoresonators, one can generate highly confined electromagnetic modes. Controlled fabrication of TMDC nanoresonators does not only enhance the material’s intrinsic nonlinear response, but also allows for spatially shaping the emission via nanoresonator arrays. Here we fabricate patterned WS2 disks that support a high internal resonant electric field and show strong enhancement of second harmonic (SH) generation in the visible regime. In addition, we assemble the WS2 disks in arrays to spatially direct the coherent SH emission, in analogy to phased array antennas. Finally, we investigate and discuss drastic differences in the areal emission origin and intensity of the measured SH signals, which we find to depend on material variations of the used bulk WS2.
Flexible, Free-Standing Polymer Membranes Sensitized by CsPbX3 Nanocrystals as Gain Media for Low Threshold, Multicolor Light Amplification
Athanasiou, Modestos; Manoli, Andreas; Papagiorgis, Paris; et al. (2022)
ACS Photonics
Lead halide perovskite nanocrystals (NCs) are highly suitable active media for solution-processed lasers in the visible spectrum, owing to the wide tunability of their emission from blue to red via facile ion-exchange reactions. Their outstanding optical gain properties and the suppressed nonradiative recombination losses stem from their defect-tolerant nature. In this work, we demonstrate flexible waveguides combining the transparent, bioplastic, polymer cellulose acetate with green CsPbBr$_3$ or red-emitting CsPb(Br,I)$_3$ NCs in simple solution-processed architectures based on polymer-NC multilayers deposited on polymer micro-slabs. Experiments and simulations indicate that the employment of the thin, free-standing membranes results in confined electrical fields, enhanced by 2 orders of magnitude compared to identical multilayer stacks deposited on conventional, rigid quartz substrates. As a result, the polymer structures exhibit improved amplified emission characteristics under nanosecond excitation, with amplified spontaneous emission (ASE) thresholds down to ∼95 μJ cm$^{–2}$ and ∼70 μJ cm$^{–2}$ and high net modal gain up to ∼450 and ∼630 cm$^{–1}$ in the green and red parts of the spectrum, respectively. The optimized gain properties are accompanied by a notable improvement of the ASE operational stability due to the low thermal resistance of the substrate-less membranes and the intimate thermal contact between the polymer and the NCs. Their application potential is further highlighted by the membrane’s ability to sustain dual-color ASE in the green and red parts of the spectrum through excitation by a single UV source, activate underwater stimulated emission, and operate as efficient white light downconverters of commercial blue LEDs, producing high-quality white light emission, 115% of the NTSC color gamut.
Fast Diffusion of Spin Polarized Excitons in Organic-Inorganic Lead Halide Perovskites
Anghel, Sergiu; Poshakinskiy, Alexander V.; Yakovlev, Dmitri R.; et al. (2023)
ACS Photonics
The hybrid organic-inorganic lead halide perovskites have recently attracted tremendous attention from the condensed matter and nanotechnology communities. This interest arises from their intriguing optoelectronic properties with an emerging potential for light-harvesting and light-emitting applications. We investigate the spin diffusion of the excitons in FA(0.9)Cs(0.1)PbI(2.8)Br(0.2) perovskite crystals at cryogenic temperatures by employing ultrafast temporally and spatially resolved magneto-optical Kerr microscopy. We find a large exciton spin diffusion coefficient on the order of similar to 100 cm(2)/s. The spin polarization signal has a very intricate dependence on the pump power & horbar;beyond a certain pump power threshold, an anomalous, nonlinear spatial and temporal dependence is observed. These experimental findings are modeled within the framework of the kinetic theory and are explained by a memory effect. Specifically, a spatial and temporal temperature variation induced by the pump pulse implies a variation of the exciton spin lifetime.
Second-Harmonic Enhancement with Mie Resonances in Perovskite Nanoparticles
Timpu, Flavia; Sergeyev, Anton; Hendricks, Nicholas R.; et al. (2017)
ACS Photonics

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Journal: ACS Photonics

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