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Unresolved-Sideband Optomechanics with Hexagonal Boron Nitride: Induced Transparency, Gain, and Frequency Combs
Authors:
Francesco Fogliano,
Thibaud Ruelle,
David Jaeger,
Martino Poggio
Abstract:
Optomechanically induced transparency (OMIT) is usually modeled and studied in the resolved-sideband regime, but many compact microcavity platforms operate in the unresolved-sideband limit $(κ\gg Ω_m)$. Here we investigate OMIT in this regime using a tunable fiber-based Fabry-Perot microcavity coupled to a suspended hexagonal boron nitride (hBN) drum resonator in a membrane-in-the-middle geometry.…
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Optomechanically induced transparency (OMIT) is usually modeled and studied in the resolved-sideband regime, but many compact microcavity platforms operate in the unresolved-sideband limit $(κ\gg Ω_m)$. Here we investigate OMIT in this regime using a tunable fiber-based Fabry-Perot microcavity coupled to a suspended hexagonal boron nitride (hBN) drum resonator in a membrane-in-the-middle geometry. The system achieves a large single-photon coupling rate of $g_0/2π\sim 180$ kHz and exhibits strong radiation-pressure backaction. By measuring OMIT spectra as a function of pump power and cavity detuning, we observe a crossover from a transparency-like dip to a gain feature in the reflected response. These maps are quantitatively reproduced by the full linearized optomechanical response, demonstrating the breakdown of the standard rotating-wave approximation used in the resolved-sideband limit. Finally, we drive the system into a nonlinear regime to generate optomechanical frequency combs. These results establish hBN fiber-cavities as a versatile architecture for unresolved-sideband optomechanics, nonlinear dynamics, and hybrid device integration.
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Submitted 30 June, 2026;
originally announced June 2026.
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OSCAR: An Ovipositor-Inspired Self-Propelling Capsule Robot for Colonoscopy
Authors:
Mostafa A. Atalla,
Anand S. Sekar,
Remi van Starkenburg,
David J. Jager,
Aimée Sakes,
Michaël Wiertlewski,
Paul Breedveld
Abstract:
Self-propelling robotic capsules eliminate shaft looping of conventional colonoscopy, reducing patient discomfort. However, reliably moving within the slippery, viscoelastic environment of the colon remains a significant challenge. We present OSCAR, an ovipositor-inspired self-propelling capsule robot that translates the transport strategy of parasitic wasps into a propulsion mechanism for colonos…
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Self-propelling robotic capsules eliminate shaft looping of conventional colonoscopy, reducing patient discomfort. However, reliably moving within the slippery, viscoelastic environment of the colon remains a significant challenge. We present OSCAR, an ovipositor-inspired self-propelling capsule robot that translates the transport strategy of parasitic wasps into a propulsion mechanism for colonoscopy. OSCAR mechanically encodes the ovipositor-inspired motion pattern through a spring-loaded cam system that drives twelve circumferential sliders in a coordinated, phase-shifted sequence. By tuning the motion profile to maximize the retract phase relative to the advance phase, the capsule creates a controlled friction anisotropy at the interface that generates net forward thrust. We developed an analytical model incorporating a Kelvin-Voigt formulation to capture the viscoelastic stick--slip interactions between the sliders and the tissue, linking the asymmetry between advance and retract phase durations to mean thrust, and slider-reversal synchronization to thrust stability. Comprehensive force characterization experiments in ex-vivo porcine colon revealed a mean steady-state traction force of 0.85 N, closely matching the model. Furthermore, experiments confirmed that thrust generation is speed-independent and scales linearly with the phase asymmetry, in agreement with theoretical predictions, underscoring the capsule's predictable performance and scalability. In locomotion validation experiments, OSCAR demonstrated robust performance, achieving an average speed of 3.08 mm/s, a velocity sufficient to match the cecal intubation times of conventional colonoscopy. By coupling phase-encoded friction anisotropy with a predictive model, OSCAR delivers controllable thrust generation at low normal loads, enabling safer and more robust self-propelling locomotion for robotic capsule colonoscopy.
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Submitted 16 February, 2026;
originally announced February 2026.
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Field measurements reveal insights into the impact of turbulent wind on loads experienced by parabolic trough solar collectors
Authors:
Ulrike Egerer,
Scott Dana,
David Jager,
Brooke J. Stanislawski,
Geng Xia,
Shashank Yellapantula
Abstract:
To ensure efficient and reliable operation of a concentrating solar-thermal power (CSP) plant, its solar collector field needs to accurately focus sunlight. The optical efficiency and structural integrity of the solar collectors is significantly influenced by wind conditions in the field. In this study, we present insights into dynamic wind loading on parabolic trough CSP collectors. We derive nov…
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To ensure efficient and reliable operation of a concentrating solar-thermal power (CSP) plant, its solar collector field needs to accurately focus sunlight. The optical efficiency and structural integrity of the solar collectors is significantly influenced by wind conditions in the field. In this study, we present insights into dynamic wind loading on parabolic trough CSP collectors. We derive novel conclusions by analyzing a first-of-a-kind measurement campaign of wind and structural loads, performed at an operational CSP plant. Previous research primarily relied on wind tunnel tests and simulations, leaving uncertainty about wind loading effects in operational settings. We demonstrate that the parabolic trough field significantly alters the turbulent wind field within the collector field, especially under winds perpendicular to the trough rows. Our measurements within the trough field show reduced wind speeds, changes in wind direction and turbulence properties, and vortex shedding from the trough assemblies. These modifications to the wind field directly impact both static and dynamic support structure loads. Our measurements reveal higher wind loads on trough assemblies compared to those observed previously in wind tunnel tests. The insights from this study offer a novel perspective on our understanding of wind-driven loads on CSP collectors. By informing the development of next-generation design tools and models, this research paves the way for enhanced structural integrity and improved optical performance in future parabolic trough systems.
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Submitted 6 June, 2024; v1 submitted 23 January, 2024;
originally announced January 2024.
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Mechanical mode imaging of a high-Q hybrid hBN/Si$_3$N$_4$ resonator
Authors:
David Jaeger,
Francesco Fogliano,
Thibaud Ruelle,
Aris Lafranca,
Floris Braakman,
Martino Poggio
Abstract:
We image and characterize the mechanical modes of a 2D drum resonator made of hBN suspended over a high-stress Si$_3$N$_4$ membrane. Our measurements demonstrate hybridization between various modes of the hBN resonator and those of the Si$_3$N$_4$ membrane. The measured resonance frequencies and spatial profiles of the modes are consistent with finite-element simulations based on an idealized geom…
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We image and characterize the mechanical modes of a 2D drum resonator made of hBN suspended over a high-stress Si$_3$N$_4$ membrane. Our measurements demonstrate hybridization between various modes of the hBN resonator and those of the Si$_3$N$_4$ membrane. The measured resonance frequencies and spatial profiles of the modes are consistent with finite-element simulations based on an idealized geometry. Spectra of the thermal motion reveal that, depending on the degree of hybridization with modes of the heavier and higher-quality-factor Si$_3$N$_4$ membrane, the quality factors and the motional mass of the hBN drum modes can be shifted by orders of magnitude. This effect could be exploited to engineer hybrid drum/membrane modes that combine the low motional mass of 2D materials with the high quality factor of Si$_3$N$_4$ membranes for optomechanical or sensing applications.
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Submitted 10 January, 2023;
originally announced January 2023.
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A tunable fiber Fabry-Perot cavity for hybrid optomechanics stabilized at 4 K
Authors:
Thibaud Ruelle,
David Jaeger,
Francesco Fogliano,
Floris Braakman,
Martino Poggio
Abstract:
We describe an apparatus for the implementation of hybrid optomechanical systems at 4 K. The platform is based on a high-finesse, micrometer-scale fiber Fabry-Perot cavity, which can be widely tuned using piezoelectric positioners. A mechanical resonator can be positioned within the cavity in the object-in-the-middle configuration by a second set of positioners. A high level of stability is achiev…
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We describe an apparatus for the implementation of hybrid optomechanical systems at 4 K. The platform is based on a high-finesse, micrometer-scale fiber Fabry-Perot cavity, which can be widely tuned using piezoelectric positioners. A mechanical resonator can be positioned within the cavity in the object-in-the-middle configuration by a second set of positioners. A high level of stability is achieved without sacrificing either performance or tunability, through the combination of a stiff mechanical design, passive vibration isolation, and an active Pound-Drever-Hall feedback lock incorporating a reconfigurable digital filter. The stability of the cavity length is demonstrated to be better than a few picometers over many hours both at room temperature and at 4 K.
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Submitted 6 May, 2022;
originally announced May 2022.
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How reproducible are methods to measure the dynamic viscoelastic properties of poroelastic media?
Authors:
Paolo Bonfiglio,
Francesco Pompoli,
Kirill V. Horoshenkov,
Mahmud Iskandar B Seth A Rahim,
Luc Jaouen,
Julia Rodenas,
Francois-Xavier Becot,
Emmanuel Gourdon,
Dirk Jaeger,
Volker Kursch,
Maurizio Tarello,
Nicolaas Bernardus Roozen,
Christ Glorieux,
Fabrizio Ferrian,
Pierre Leroy,
Francesco Briatico Vangosa,
Nicolas Dauchez,
Felix Foucart,
Lei Lei,
Kevin Carillo,
Olivier Doutres,
Franck Sgard,
Raymond Panneton,
Kevin Verdiere,
Claudio Bertolini1
, et al. (8 additional authors not shown)
Abstract:
There is a considerable number of research publications on the acoustical properties of porous media with an elastic frame. A simple search through the Web of ScienceTM (last accessed 21 March 2018) suggests that there are at least 819 publications which deal with the acoustics of poroelastic media. A majority of these researches require accurate knowledge of the elastic properties over a broad fr…
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There is a considerable number of research publications on the acoustical properties of porous media with an elastic frame. A simple search through the Web of ScienceTM (last accessed 21 March 2018) suggests that there are at least 819 publications which deal with the acoustics of poroelastic media. A majority of these researches require accurate knowledge of the elastic properties over a broad frequency range. However, the accuracy of the measurement of the dynamic elastic properties of poroelastic media has been a contentious issue. The novelty of this paper is that it studies the reproducibility of some popular experimental methods which are used routinely to measure the key elastic properties such as the dynamic Young's modulus, loss factor and Poisson ratio of poroelastic media. In this paper, fourteen independent sets of laboratory measurements were performed on specimens of the same porous materials. The results from these measurements suggest that the reproducibility of this type of experimental method is poor. This work can be helpful to suggest improvements which can be developed to harmonize the way the elastic properties of poroelastic media are measured worldwide.
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Submitted 23 May, 2018;
originally announced May 2018.