Choice of the Miniature Inertial Optomechanical Sensor Geometric Parameters with the Help of Their Mechanical Characteristics Modelling

In this paper, the mechanical characteristics of a miniature optomechanical accelerometer, similar to those proposed for a wide range of applications, have been investigated. With the help of numerical modelling, characteristics such as eigenfrequencies, quality factor, displacement magnitude, normalized translations, normalized rotations versus eigenfrequencies, as well as spatial distributions of the azimuthal and axial displacements and stored energy density in a wide frequency range starting from the stationary case have been obtained. Dependencies of the main mechanical characteristics versus the minimal and maximal system dimensions have been plotted. Geometries of the optomechanical accelerometers with micron size parts providing the low and the high first eigenfrequencies are presented. It is shown that via the choice of the geometrical parameters, the minimal measured acceleration level can be raised substantially

A laser dilatometer setup to characterize dimensionally stable materials from 100 K to 300 K

In our structural dimensional metrology laboratory, we implemented a setup to determine coefficients of thermal expansions (CTE) of ultra-stable materials at temperatures from 300 K down to 100 K. Such low CTE materials are important for dimensionally stable structures in space and terrestrial applications, e. g. to enable precise measurements. This CTE characterization is done in the 10 ppb/K (10·10-9 K-1) range by applying small temperature variation around dedicated absolute temperatures. In order to accommodate arbitrary sample materials, we bounce light off mirrors attached to the sample by custom mounts. The light and therefore the thermal-induced length variations is then analyzed by an interferometer with sub-nanometer sensitivity. Here, we present a more detailed investigation of a process during sample measurements using differential wavefront sensing (DWS)

A Novel Integrated Multifunction Micro-Sensor for Three-Dimensional Micro-Force Measurements

An integrated multifunction micro-sensor for three-dimensional micro-force precision measurement under different pressure and temperature conditions is introduced in this paper. The integrated sensor consists of three kinds of sensors: a three-dimensional micro-force sensor, an absolute pressure sensor and a temperature sensor. The integrated multifunction micro-sensor is fabricated on silicon wafers by micromachining technology. Different doping doses of boron ion, placement and structure of resistors are tested for the force sensor, pressure sensor and temperature sensor to minimize the cross interference and optimize the properties. A glass optical fiber, with a ladder structure and sharp tip etched by buffer oxide etch solution, is glued on the micro-force sensor chip as the tactile probe. Experimental results show that the minimum force that can be detected by the force sensor is 300 nN; the lateral sensitivity of the force sensor is 0.4582 mV/μN; the probe length is linearly proportional to sensitivity of the micro-force sensor in lateral; the sensitivity of the pressure sensor is 0.11 mv/KPa; the sensitivity of the temperature sensor is 5.836 × 10−3 KΩ/°C. Thus it is a cost-effective method to fabricate integrated multifunction micro-sensors with different measurement ranges that could be used in many fields

Optomechanical resonator-enhanced atom interferometry

Matter-wave interferometry and spectroscopy of optomechanical resonators offer complementary advantages. Interferometry with cold atoms is employed for accurate and long-term stable measurements, yet it is challenged by its dynamic range and cyclic acquisition. Spectroscopy of optomechanical resonators features continuous signals with large dynamic range, however it is generally subject to drifts. In this work, we combine the advantages of both devices. Measuring the motion of a mirror and matter waves interferometrically with respect to a joint reference allows us to operate an atomic gravimeter in a seismically noisy environment otherwise inhibiting readout of its phase. Our method is applicable to a variety of quantum sensors and shows large potential for improvements of both elements by quantum engineering. © 2020, The Author(s)

MaQuIs—Concept for a Mars Quantum Gravity Mission

The aim of this paper is to present the concept of a dedicated gravity field mission for the planet Mars, the Mars Quantum Gravity Mission (MaQuIs). The mission is targeted at improving the data on the gravitational field of Mars, enabling studies on planetary dynamics, seasonal changes, and subsurface water reservoirs. MaQuIs follows well known mission scenarios, currently deployed for Earth, and includes state-of-the-art quantum technologies to enhance the gained scientific signal

ACUTE EFFECTS OF CAFFEINE CONSUMPTION ON HEART RATE VARIABILITY AT REST

ACUTE EFFECTS OF CAFFEINE CONSUMPTION ON HEART RATE VARIABILITY AT REST J.E. Kumanchik, J.R. McNeal, and N.H. Lawton Eastern Washington University, Cheney, WA The cardiovascular system (CVS) is primarily controlled by the autonomic nervous system (ANS). Heart rate variability (HRV) is considered a balance between sympathetic and parasympathetic activity of the ANS that regulates heart rate, and thus a determinant of cardiovascular health. Therefore, measurement of HRV can provide insight into the autonomic function of the CVS and factors that influence it, such as caffeine consumption. PURPOSE: This study sought to determine the acute effects of caffeine consumption on HRV at rest. METHODS: A group of 23 apparently healthy male and female adults (21-27 years) were used for this study. Following 5 min of quiet sitting, subjects underwent an initial electrocardiogram (ECG) recording at rest for 3 min, using a 3-lead ECG. Subjects then consumed a dosage of caffeine equivalent to 2 mg per 1 kg of body mass using caffeinated jellybeans. Thirty minutes following ingestion, subjects underwent a second ECG recording at rest for 3 min. From the ECG record, duration between successive R-R waves was measured to determine HRV before and after caffeine consumption. A paired-samples t-test was conducted to compare HRV at rest between no caffeine (NC) and caffeine (C) conditions. Two independent-samples t-tests were conducted to determine if there were significant differences in HRV at rest in NC and C conditions between sexes. RESULTS: All HRV data are reported in the unit of milliseconds (msec). Coefficient of variation (CV) is also reported. There was a significant difference in HRV between NC (.76 ± .13 msec; CV = 17.1%) and C (.81 ± .15 msec; CV = 18.5%) conditions (p \u3c .001). There was no significant difference in HRV between sex in the NC condition (Male = .77 ± .14 msec, CV = 18.1%; Female = .75 ± .13 msec, CV = 17.3%; p = .689) or the C condition (Male = .83 ± .15 msec, CV = 18.07%; Female = .79 ± .15 msec, CV = 18.9%; p = .547). CONCLUSION: These data suggest caffeine does have an effect on HRV at rest. Specifically, the results from this study suggest that caffeine consumption decreases HRV at rest, regardless of sex. Researchers or clinicians using HRV as a diagnostic tool should be aware that caffeine ingestion can reduce HRV, and should consider controlling for caffeine ingestion in their protocols

Opto-Mechanical Inertial Sensors (OMIS) for High Temporal Resolution Gravimetry

Gravity field measurement by free-falling atoms has the potential for very high stability over time as the measurement exposes a direct, fundamental relationship between mass and acceleration. However, the measurement rate of the current state-of-the-art limits the performance at short timescales (greater than 1 Hz). Classical inertial sensors operate at much faster response times and are thus natural companions for free-falling atom sensors. Such a hybrid device would gain the ultra-high stability of the free-falling atom sensor while greatly extending the bandwidth to higher frequency using the classical sensor. This requires the stable bandwidth of both devices to overlap sufficiently. We have developed opto-mechanical inertial sensors (OMIS) with good long term stability for just this purpose. The sensors are made of highly stable fused silica material, feature a monolithic optical cavity for displacement readout, and utilize a laser diode stabilized to a molecular reference. With no temperature control and only the thermal shielding provided by the vacuum chamber, this device is stable down to 0.1 Hz which overlaps with the bandwidth of free-falling atom sensors. The OMIS are self-calibrating by converting the fundamental resonances of a molecular gas into length using the free-spectral range of the optical cavity, FSR = c/2nL, and then sampling the OMIS mechanical damping rate and resonance frequency using a nearby piezo. This acceleration calibration is potentially transferable to a companion free-falling atom sensor. Readout is performed by modulating the cavity length of the OMIS with one cavity mirror being the OMIS itself and the other being a high frequency resonator. The high frequency resonator is driven by a nearby piezo well above the response rate of the OMIS and acts like an ultrastable quartz clock. The resulting highly stable tone is demodulated by the readout electronics. For the low finesse optical cavity used here, this yields a displacement resolution of 2x10-13 m/rtHz and a high frequency acceleration resolution of 400 ng /rtHz. At 0.1 Hz the acceleration resolution is 1.5 mug /rtHz limited by the stability of our vibration isolation stage. The OMIS dimensions are about 30 mm x 30 mm x 5 mm and can be fiber coupled to enable co-location with other sensors or as standalone devices for future gravimetry both on Earth and in spac