arXiv subjects

Seyed Khalil Alavi

Publications and source records attributed to Seyed Khalil Alavi.

5 recordsLinked to original sources

arXiv2026

Interference-Based 3D Optical Cold Damping of a Levitated Nanoparticle

Achieving efficient three-dimensional feedback cooling of levitated nanoparticles is a key requirement for precision sensing and quantum control in levitated optomechanics. Here we demonstrate three-dimensional optical feedback cooling of a levitated nanoparticle using an interference-enhanced optical force generated within a single beam path. In this scheme, a weak auxiliary field co-propagates with the trapping tweezer and interferes with it to produce a tunable optical force that enables cold damping along all three center-of-mass motional axes without additional beam paths or trap reconfiguration. Using this approach, we cool a 142-nm-diameter silica nanoparticle in high vacuum to effective temperatures of 625.8, 711.6, and 19.9 mK along the $x$, $y$, and $z$ directions, respectively, at a pressure of $8.5\times10^{-6}$ mbar. The cooling dynamics and their dependence on feedback gain and pressure are well described by a cold-damping model. Because the feedback force is generated optically, the scheme does not rely on electrical actuation and is directly compatible with neutral particles. These results establish interference-based optical forces as a simple and broadly applicable mechanism for three-dimensional feedback control in levitated optomechanics, with a clear pathway toward the quantum regime under improved vacuum and detection conditions.

physics.optics↗

arXiv2025

Compact vacuum levitation and control platform with a single 3D-printed fiber lens

Levitated dielectric particles in a vacuum have emerged as a new platform in quantum science, with applications ranging from precision acceleration and force sensing to testing quantum physics beyond the microscopic domain. Traditionally, particle levitation relies on optical tweezers formed by tightly focused laser beams, which typically require multiple bulk optical elements aligned in free space, limiting robustness and scalability of the system. To address these challenges, we employ a single optical fiber equipped with a high numerical aperture (NA) lens directly printed onto the fiber facet. This enables a compact yet robust optical levitation and detection system composed entirely of fiber-based components, eliminating the need for complex alignment. The high NA of the printed lens allows stable single-beam trapping of a dielectric nanoparticle in a vacuum, even while the fiber is in controlled motion. The high NA also allows for collecting scattered light from the particle with excellent collection efficiency, thus enabling efficient detection and feedback stabilization of the particle's motion. Our platform paves the way for practical and portable sensors based on levitated particles and provides simple yet elegant solutions to complex experiments requiring the integration of levitated particles.

physics.optics↗

arXiv2025

Optical levitation of fluorescent silicon carbide nanoparticles in vacuum

Levitated optomechanics is an emerging field in quantum science that explores the quantum motion of mesoscopic particles levitated in a vacuum. Expanding this approach to particles with intrinsic quantum defects opens new opportunities for quantum sensing and nontrivial quantum state generation. Here, we explore silicon carbide (SiC) nanoparticles as a promising platform that offers a range of controllable quantum defects and material tunability. We demonstrate stable optical levitation of 3C-polytype SiC nanoparticles containing single photon emitters in a vacuum. We observe stable fluorescence from the levitated particle, confirming the preservation of the emitters in the levitated state. We also investigate particle loss at low pressure and explore thermal annealing as a potential method to improve trapping stability. Our results establish SiC as a viable platform for levitated optomechanics, providing additional quantum degrees of freedom and material engineering capabilities.

physics.optics↗

arXiv2024

Enhanced optomechanical coupling between an optically levitated particle and an ultrahigh Q optical microcavity

Exploring the dynamics of an optically levitated dielectric micro- and nanoparticle is an exciting new subject in quantum science. Recent years have witnessed rapid advancements in attaining quantum-limited optical detection and control of a nanoscale particle by coupling its motion to a high-finesse optical cavity in the resolved-sideband regime. In order to control the particle deeper in the quantum regime, it is necessary to significantly enhance the coupling between the particle and the cavity. Here, we present a novel platform that can allow for achieving this. Our system consists of a conventional optical tweezer and a toroidal optical microcavity with an ultrahigh quality (Q) factor. The optomechanical coupling between the particle and the cavity is established by placing the particle in the near field of the cavity. The significantly reduced mode volume allows us to achieve a 50-fold increase in the single photon optomechanical coupling compared to a conventional Fabry-Pérot cavity with macroscopic mirrors, while ultralow loss of the cavity brings the system close to the resolved-sideband regime. Our approach paves the way for enabling quantum experiments on levitated mesoscopic particles with high quantum cooperativity near the resolved-sideband regime.

physics.optics↗

arXiv2016

High Finesse Fiber Fabry-Perot Cavities: Stabilization and Mode Matching Analysis

Fiber Fabry-Perot cavities, formed by micro-machined mirrors on the end-facets of optical fibers, are used in an increasing number of technical and scientific applications, where they typically require precise stabilization of their optical resonances. Here, we study two different approaches to construct fiber Fabry-Perot resonators and stabilize their length for experiments in cavity quantum electrodynamics with neutral atoms. A piezo-mechanically actuated cavity with feedback based on the Pound-Drever-Hall locking technique is compared to a novel rigid cavity design that makes use of the high passive stability of a monolithic cavity spacer and employs thermal self-locking and external temperature tuning. Furthermore, we present a general analysis of the mode matching problem in fiber Fabry-Perot cavities, which explains the asymmetry in their reflective line shapes and has important implications for the optimal alignment of the fiber resonators. Finally, we discuss the issue of fiber-generated background photons. We expect that our results contribute towards the integration of high-finesse fiber Fabry-Perot cavities into compact and robust quantum-enabled devices in the future.

physics.atom-ph↗