Optical Trapping of High-Aspect-Ratio NaYF Hexagonal Prisms for kHz-MHz Gravitational Wave Detectors.

We present experimental results on optical trapping of Yb-doped ß-NaYF subwavelength-thickness high-aspect-ratio hexagonal prisms with a micron-scale radius. The prisms are trapped in vacuum using an optical standing wave, with the normal vector to their face oriented along the beam propagation direction, yielding much higher trapping frequencies than those typically achieved with microspheres of similar mass. This platelike geometry simultaneously enables trapping with low photon-recoil-heating, high mass, and high trap frequency, potentially leading to advances in high frequency gravitational wave searches in the Levitated Sensor Detector, currently under construction. The material used here has previously been shown to exhibit internal cooling via laser refrigeration when optically trapped and illuminated with light of suitable wavelength. Employing such laser refrigeration methods in the context of our work may enable higher trapping intensity and thus higher trap frequencies for gravitational wave searches approaching the several hundred kilohertz range.

Passive laser power stabilization via an optical spring.

Metrology experiments can be limited by the noise produced by the laser involved via small fluctuations in the laser's power or frequency. Typically, active power stabilization schemes consisting of an in-loop sensor and a feedback control loop are employed. Those schemes are fundamentally limited by shot noise coupling at the in-loop sensor. In this Letter, we propose to use the optical spring effect to passively stabilize the classical power fluctuations of a laser beam. In a proof of principle experiment, we show that the relative power noise of the laser is stabilized from approximately 2 × 10-5 Hz-1/2 to a minimum value of 1.6 × 10-7 Hz-1/2, corresponding to the power noise reduction by a factor of 125. The bandwidth at which stabilization occurs ranges from 400 Hz to 100 kHz. The work reported in this Letter further paves the way for high power laser stability techniques which could be implemented in optomechanical experiments and in gravitational wave detectors.

Searching for New Physics with a Levitated-Sensor-Based Gravitational-Wave Detector.

The levitated sensor detector (LSD) is a compact resonant gravitational-wave (GW) detector based on optically trapped dielectric particles that is under construction. The LSD sensitivity has more favorable frequency scaling at high frequencies compared to laser interferometer detectors such as LIGO and VIRGO. We propose a method to substantially improve the sensitivity by optically levitating a multilayered stack of dielectric discs. These stacks allow the use of a more massive levitated object while exhibiting minimal photon recoil heating due to light scattering. Over an order of magnitude of unexplored frequency space for GWs above 10 kHz is accessible with an instrument 10 to 100 meters in size. Particularly motivated sources in this frequency range are gravitationally bound states of the axion from quantum chromodynamics with decay constant near the grand unified theory scale that form through black hole superradiance and annihilate to GWs. The LSD is also sensitive to GWs from binary coalescence of sub-solar-mass primordial black holes and as-yet unexplored new physics in the high-frequency GW window.

Evaluation of the relationship between dermatoglyphics and mandibular third molar impaction: A cross-sectional study.

Background: Dermatoglyphics can be utilised in clinical settings to identify those who are more likely to have impacted teeth. Additionally, dermatoglyphics looks to have potential as a non-invasive diagnostic method for predicting the presence or absence of an impacted tooth. The goal of this study was to look at the most common dermatoglyphic pattern in people who had or didn't have an impacted mandibular third molar teeth and see if there was a dermatoglyphic signature. Methods: A cross-sectional study with 180 participants was conducted (90 cases and 90 controls). The rolling impression technique was used to apply blue duplicating ink to participants' fingertips, which was then recorded. There was an increase in the frequency of the whorl-plain pattern in the right-hand ring finger (60%; p=0.028) and left-hand little finger (33.3%; p=0.009), as well as the loop-ulnar pattern in the right-hand middle finger (74.4%; p=0.024) in individuals with a predisposition to the presence of impacted teeth. Results: The left-hand little finger was found to be the most predictive for impaction in a forward stepwise binary logistic regression analysis. Conclusions: Dermatoglyphics could be used as a non-invasive sign to predict whether or not a tooth is affected. Its value comes in early detection, which helps to avoid the surgical problems that come with symptomatic extraction of an impacted tooth.

Laser power stabilization via radiation pressure.

This Letter reports the experimental realization of a novel, to the best of our knowledge, active power stabilization scheme in which laser power fluctuations are sensed via the radiation pressure driven motion they induce on a movable mirror. The mirror position and its fluctuations were determined by means of a weak auxiliary laser beam and a Michelson interferometer, which formed the in-loop sensor of the power stabilization feedback control system. This sensing technique exploits a nondemolition measurement, which can result in higher sensitivity for power fluctuations than direct, and hence destructive, detection. Here we used this new scheme in a proof-of-concept experiment to demonstrate power stabilization in the frequency range from 1 Hz to 10 kHz, limited at low frequencies by the thermal noise of the movable mirror at room temperature.

Wide-area transepithelial sampling in adjunct to forceps biopsy increases the absolute detection rates of Barrett's oesophagus and oesophageal dysplasia: a meta-analysis and systematic review.

BACKGROUND: Wide-area transepithelial sampling (WATS) is a new technique that uses an abrasive brush to obtain samples from a larger surface area of the oesophagus. Studies have shown promising results that WATS in adjunct to forceps biopsy (FB) increases the detection rate of Barrett's oesophagus (BE) as well as oesophageal dysplasia (ED). We conducted a systematic review and meta-analysis to compare the detection rates of BE and ED between FB and WATS in adjunct to FB. METHODS: A Literature search was done using electronic databases, including PubMed, Embase, Scopus, Cochrane and CINAHL from inception to 26 April 2020. A meta-analysis comparing detection rates of WATS in adjunct to FB versus FB using the random-effects model was done using RevMan V.5.3. RESULTS: Pooled data from 20 392 endoscopies across 11 studies showed an absolute increase in detection of 16% (95% CI 0.10% to 0.22%, p<0.00001). A relative increase of 1.62 was seen in detection rates of BE (95% CI 1.28 to 2.05, p<0.0001) when WATS was used with FB with the number needed to test (NNT) of 6.1 patients. For ED, a 2% absolute increase (95% CI 0.01 to 0.03, p=0.001) in additional diagnostic yield from WATS. A relative increase of 2.05 was seen in the detection rate of ED (95% CI 1.42 to 2.98, p=0.0001) yielding an NNT of 50 patients. CONCLUSION: Our study shows that WATS, as an adjunct to FB, improves both the absolute detection rate and relative detection rate of both BE and ED as compared to FB alone.

Measurement of quantum back action in the audio band at room temperature.

Quantum mechanics places a fundamental limit on the precision of continuous measurements. The Heisenberg uncertainty principle dictates that as the precision of a measurement of an observable (for example, position) increases, back action creates increased uncertainty in the conjugate variable (for example, momentum). In interferometric gravitational-wave detectors, higher laser powers reduce the position uncertainty created by shot noise (the photon-counting error caused by the quantum nature of the laser) but necessarily do so at the expense of back action in the form of quantum radiation pressure noise (QRPN)1. Once at design sensitivity, the gravitational-wave detectors Advanced LIGO2, VIRGO3 and KAGRA4 will be limited by QRPN at frequencies between 10 hertz and 100 hertz. There exist several proposals to improve the sensitivity of gravitational-wave detectors by mitigating QRPN5-10, but until now no platform has allowed for experimental tests of these ideas. Here we present a broadband measurement of QRPN at room temperature at frequencies relevant to gravitational-wave detectors. The noise spectrum obtained shows effects due to QRPN between about 2 kilohertz and 100 kilohertz, and the measured magnitude of QRPN agrees with our model. We now have a testbed for studying techniques with which to mitigate quantum back action, such as variational readout and squeezed light injection7, with the aim of improving the sensitivity of future gravitational-wave detectors.