Alexander Fieguth

All Publications

• Dipole moment background measurement and suppression for levitated charge sensors. Science advances Priel, N., Fieguth, A., Blakemore, C. P., Hough, E., Kawasaki, A., Martin, D., Venugopalan, G., Gratta, G. 2022; 8 (41): eabo2361

  Abstract

  Optically levitated macroscopic objects are a powerful tool in the field of force sensing, owing to high sensitivity, absolute force calibration, environmental isolation, and the advanced degree of control over their dynamics that have been achieved. However, limitations arise from the spurious forces caused by electrical polarization effects that, even for nominally neutral objects, affect the force sensing because of the interaction of dipole moments with gradients of external electric fields. Here, we introduce a technique to measure, model, and eliminate dipole moment interactions, limiting the performance of sensors using levitated objects. This process leads to a noise-limited measurement with a sensitivity of 3.3 * 10-5 e. As a demonstration, this is applied to the search for unknown charges of a magnitude much below that of an electron or for exceedingly small unbalances between electron and proton charges.

  View details for DOI 10.1126/sciadv.abo2361

  View details for PubMedID 36240282

• Librational feedback cooling PHYSICAL REVIEW A Blakemore, C. P., Martin, D., Fieguth, A., Priel, N., Venugopalan, G., Kawasaki, A., Gratta, G. 2022; 106 (2)

  View details for DOI 10.1103/PhysRevA.106.023503

  View details for Web of Science ID 000836411200011

• Search for non-Newtonian interactions at micrometer scale with a levitated test mass PHYSICAL REVIEW D Blakemore, C. P., Fieguth, A., Kawasaki, A., Priel, N., Martin, D., Rider, A. D., Wang, Q., Gratta, G. 2021; 104 (6)

  View details for DOI 10.1103/PhysRevD.104.L061101

  View details for Web of Science ID 000692101900029

• Detection prospects for the second-order weak decays of Xe-124 in multi-tonne xenon time projection chambers EUROPEAN PHYSICAL JOURNAL C Wittweg, C., Lenardo, B., Fieguth, A., Weinheimer, C. 2020; 80 (12)

  View details for DOI 10.1140/epjc/s10052-020-08726-w

  View details for Web of Science ID 000600229800002

• High sensitivity, levitated microsphere apparatus for short-distance force measurements. The Review of scientific instruments Kawasaki, A., Fieguth, A., Priel, N., Blakemore, C. P., Martin, D., Gratta, G. 2020; 91 (8): 083201

  Abstract

  A high sensitivity force sensor based on dielectric microspheres in vacuum, optically trapped by a single, upward-propagating laser beam, is described. Off-axis parabolic mirrors are used both to focus the 1064 nm trapping beam and to recollimate it to provide information on the horizontal position of the microsphere. The vertical degree of freedom is readout by forming an interferometer between the light retroreflected by the microsphere and a reference beam, hence eliminating the need for auxiliary beams. The focus of the trapping beam has a 1/E2 radius of 3.2 m and small non-Gaussian tails, suitable for bringing devices close to the trapped microsphere without disturbing the optical field. Electrodes surrounding the trapping region provide excellent control of the electric field, which can be used to drive the translational degrees of freedom of a charged microsphere and the rotational degrees of freedom of a neutral microsphere, coupling to its electric dipole moment. With this control, the charge state can be determined with single electron precision, the mass of individual microspheres can be measured, and empirical calibrations of the force sensitivity can be made for each microsphere. A force noise of <1 * 10-17 N/Hz, which is comparable to previous reports, is measured on all three degrees of freedom for 4.7 m diameter, 84 pg silica microspheres. Various devices have been brought within 1.6 m of the surface of a trapped microsphere. Metrology in the trapping region is provided by two custom-designed microscopes providing views in the horizontal and one of the vertical planes. The apparatus opens the way to performing high sensitivity three-dimensional force measurements at a short distance.

  View details for DOI 10.1063/5.0011759

  View details for PubMedID 32872897

• Absolute pressure and gas species identification with an optically levitated rotor JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B Blakemore, C. P., Martin, D., Fieguth, A., Kawasaki, A., Priel, N., Rider, A. D., Gratta, G. 2020; 38 (2)

  View details for DOI 10.1116/1.5139638

  View details for Web of Science ID 000569100800022

• Precision Mass and Density Measurement of Individual Optically Levitated Microspheres PHYSICAL REVIEW APPLIED Blakemore, C. P., Rider, A. D., Roy, S., Fieguth, A., Kawasaki, A., Priel, N., Gratta, G. 2019; 12 (2)

  View details for DOI 10.1103/PhysRevApplied.12.024037

  View details for Web of Science ID 000481614300003