Nanoparticle detection in an open-access silicon microcavity

We report on the detection of free nanoparticles in a micromachined, open-access Fabry-P\'erot microcavity. With a mirror separation of $130\,\mu$m, a radius of curvature of $1.3\,$mm, and a beam waist of $12\,\mu$m, the mode volume of our symmetric infrared cavity is smaller than $15\,$pL. The small beam waist, together with a finesse exceeding 34,000, enables the detection of nano-scale dielectric particles in high vacuum. This device allows monitoring of the motion of individual $150\,$nm radius silica nanospheres in real time. We observe strong coupling between the particles and the cavity field, a precondition for optomechanical control. We discuss the prospects for optical cooling and detection of dielectric particles smaller than $10\,$nm in radius and $1\times10^7\,$amu in mass.Comment: 4 pages, 3 figure

Towards optical cooling of silicon nanoparticles in a microcavity

Optomechanik ist ein schnell voranschreitendes Feld mit vielversprechenden Anwendungsmöglichkeiten in Tests der fundamentalen Naturgesetze, der Thermodynamik bis hin zu sehr präzisen Messungen. Technologischer Fortschritt im Bereich der Fabrikation von Mikro- und Nanooptik ermöglicht nunmehr die Erforschung neuer Parameterregime mit diesen Systemen. Insbesondere haben sich einzelne Nanoteilchen in mikroskopischen optischen Resonatoren als möglicher Weg zum Nachweis von Quanteneigenschaften auf mesoskopischen und schließlich auch makroskopischen Skalen hervorgetan. Aufgrund ihrer Größe sind sie gut geeignet, um das Superpositionsprinzip, dem viele der eigenartigen Phänomene der Quantenmechanik entspringen, experimentell zu untersuchen. Laserkühlung in optischen Resonatoren erlaubt es, die Bewegung von Nanoteilchen durch ihre Wechselwirkung mit Licht zu verlangsamen und sie auf diese Weise für Materiewelleninterferometrie vorzubereiten. Eine Reihe neuartiger Mikroresonatoren mit hoher Güte und freiem Zugang zu diesem Zweck wurde entwickelt und in einem eigens dafür erstellten Aufbau getestet. Zudem konnte eine dispersive Wechselwirkung mit der Mode beobachtet werden und die Laserkühlung in einem Massenbereich von 10^6 - 10^9 amu scheint nun in unmittelbarer Reichweite.Optomechanics is a rapidly advancing field with potential applications in many areas of research ranging from fundamental tests of physics and thermodynamics to sensing. Recently, technological advances in the fabrication of micro- and nanooptical systems have opened up new parameter regimes and hold great promise for future experiments. In particular, individual nanoparticles coupled to microcavities have emerged as a viable route towards the quantum regime on the mesoscopic and eventually even macroscopic scale. The size of the objects under investigation naturally makes them good candidates for tests of the superposition principle which is manifest in the interference of matter-waves. Cavity cooling is a way to slow down the motion of nanoparticles through their interaction with light and prepare them for interferometry. A novel set of open-access, high-finesse microcavities with small mode volumes for this purpose was characterized in a new experimental setup. Dispersive coupling of nanoparticles has been observed and paves the way for cavity cooling in the 10^6 - 10^9 amu mass range

Swiss-wide multicentre evaluation and prediction of core outcomes in arthroscopic rotator cuff repair: protocol for the ARCR_Pred cohort study

Introduction In the field of arthroscopic rotator cuff repair (ARCR), reporting standards of published studies differ dramatically, notably concerning adverse events (AEs). In addition, prognostic studies are overall methodologically poor, based on small data sets and explore only limited numbers of influencing factors. We aim to develop prognostic models for individual ARCR patients, primarily for the patient-reported assessment of shoulder function (Oxford Shoulder Score (OSS)) and the occurrence of shoulder stiffness 6 months after surgery. We also aim to evaluate the use of a consensus core event set (CES) for AEs and validate a severity classification for these events, considering the patient’s perspective.Methods and analysis A cohort of 970 primary ARCR patients will be prospectively documented from several Swiss and German orthopaedic clinics up to 24 months postoperatively. Patient clinical examinations at 6 and 12 months will include shoulder range of motion and strength (Constant Score). Tendon repair integrity status will be assessed by ultrasound at 12 months. Patient-reported questionnaires at 6, 12 and 24 months will determine functional scores (subjective shoulder value, OSS), anxiety and depression scores, working status, sports activities, and quality of life (European Quality of Life 5 Dimensions 5 Level questionnaire). AEs will be documented according to a CES. Prognostic models will be developed using an internationally supported regression methodology. Multiple prognostic factors, including patient baseline demographics, psychological, socioeconomic and clinical factors, rotator cuff integrity, concomitant local findings, and (post)operative management factors, will be investigated.Ethics and dissemination This project contributes to the development of personalised risk predictions for supporting the surgical decision process in ARCR. The consensus CES may become an international reference for the reporting of complications in clinical studies and registries. Ethical approval was obtained on 1 April 2020 from the lead ethics committee (EKNZ, Basel, Switzerland; ID: 2019-02076). All participants will provide informed written consent before enrolment in the study.Trial registration number NCT04321005.Protocol version Version 2 (13 December 2019)