arXiv subjects

Miguel Varga

Publications and source records attributed to Miguel Varga.

5 recordsLinked to original sources

arXiv2026

Upper bound to optical forces through the multipolar control of optical beams

Optical tweezers enable the manipulation of microscopic objects using light, yet the fundamental limits to the optical forces that can be exerted on matter remain unknown. Here we derive a general upper bound to the maximum optical force that can be applied to a particle, based on an expansion of electromagnetic fields into well-defined helicity multipolar modes. This method finds the optimal force for any kind of fields external to the particle, including evanescent fields. We apply the method to homogeneous spherical particles in a stable trap and identify the field distributions that saturate this bound for the trapping stiffness. We further provide experimentally accessible strategies to approach these optimal conditions, including configurations using counterpropagating and single-beam traps. Experiments demonstrate a threefold enhancement of trapping forces relative to conventional designs, while theoretical predictions indicate that order-of-magnitude improvements are achievable for larger particles and high angular momentum beams. Our results establish fundamental design principles for maximizing optical forces and define the ultimate limits of optical manipulation.

physics.optics↗

arXiv2026

On-Axis Optical Trapping with Vortex Beams: The Role of the Multipolar Decomposition

Optical trapping is a well_established, decades old technology with applications in several fields of research. The most common scenario deals with particles that tend to be centered on the brightest part of the optical trap. Consequently, the optical forces keep the particle away from the dark zones of the beam. However, this is not the case when a focused doughnut_shaped beam generates on_axis trapping. In this system, the particle is centered on the intensity minima of the laser beam and the bright annular part lies on the periphery of the particle. Researchers have shown great interest in this phenomenon due to its advantage of reducing light interaction with trapped particles and the intriguing increase in the trapping strength. This work presents experimental and theoretical results that extend the analysis of on_axis trapping with light vortex beams. Specifically, in our experiments, we trap micron_sized spherical silica (SiO2) particles in water and we measure, through the power spectrum density method, the trap stiffness constant \k{appa} generated by vortex beams with different topological charge orders. The optical forces are calculated from the exact solutions of the electromagnetic fields provided by the generalized Lorentz_Mie theory. We show a remarkable agreement between the theoretical prediction and the experimental measurements of \k{appa}. Moreover, our numerical model gives us information about the electromagnetic fields inside the particle, offering valuable insights into the influence of the electromagnetic fields present in the vortex beam trapping scenario.

physics.optics↗

arXiv2025

Controlling the centre of mass motion of levitated particles using structured wavefronts

Optically levitated particles have great potential to form the basis of novel quantum- enhanced sensors. These systems are very well suited for inertial sensing, as the particles are isolated from the environment when they are levitated at low pressures. However, there are many challenges in the experimental realization that may affect the performance of these systems. For example, optical aberrations in the wavefront of the trapping laser which arise from optical elements or misalignment have a great impact on the trapping potential. The detrimental effect of optical aberrations has not been thoroughly studied, and usually they are iteratively corrected, giving some conflicting results depending on the figures of merit that are used. In this work, we present a thorough study of the effects of structuring the wavefront of the trapping beams. We observe that clean beams, i.e. highly focused beams with unaberrated wavefronts, may be used to optimize the longitudinal frequencies, at the cost of the transversal ones. Our work is based in a combination of experimental studies using a complete basis of orthogonal polynomials (Zernike polynomials) to control the wavefront and a set of numerical calculations, which allow us to compare the impact of structured wavefronts on the quality of traps for optically levitated particles in vacuum. This will have direct applications in quantum sensing and fundamental studies of quantum mechanics, as it allows the reduction of optical backaction and thermal decoherence of the particles.

physics.optics↗

arXiv2024

Quantum-inspired clustering with light

This article introduces a novel approach to perform the simulation of a single qubit quantum algorithm using laser beams. Leveraging the polarization states of photonic qubits, and inspired by variational quantum eigensolvers, we develop a variational quantum algorithm implementing a clustering procedure following the approach proposed by some of us in SciRep 13, 13284 (2023). A key aspect of our research involves the utilization of non-orthogonal states within the photonic domain, harnessing the potential of polarization schemes to reproduce unitary circuits. By mapping these non-orthogonal states into polarization states, we achieve an efficient and versatile quantum information processing unit which serves as a clustering device for a diverse set of datasets.

quant-ph↗

arXiv2024

Versatile quadrature antenna for precise control of large electron spin ensembles in diamond

We present an easily reproducible inexpensive microwave antenna that can generate a strong and homogeneous magnetic field of arbitrary polarization, which enables fast and coherent control of electron spins over a large volume. Unlike preceding works, we present a resonant antenna that maintains its resonant behaviour regardless of the proximity of other experimental hardware components. This robustness is crucial as it enables, amongst others, using microscope objectives with short working distances to perform wide field imaging/sensing with bulk diamonds. The antenna generates a magnetic field strength of 22.3 A/m for 1 W total driving power, which doubles the power efficiency compared with previously reported patch antenna designs. The magnetic field homogeneity in a volume of $0.3 \text{mm}^3$, $0.5 \text{mm}^3$ and $1 \text{mm}^3$ is within 6\%, 8\% and 13\%, respectively. The antenna has a full width at half maximum bandwidth of $\sim$160 MHz and its resonant frequency can be tuned over a 400 MHz range via four capacitors or varactors. The antenna has been tested and found to remain within safe handling temperatures during continuous-wave operation at 8 W. The files required to reproduce this antenna, which can be built on a standard and affordable double sided PCB, are provided open-source. This work facilitates a robust and versatile piece of instrumentation, being particularly appealing for applications such as high sensitivity magnetometry and wide field imaging/sensing with Nitrogen Vacancy centers.

physics.ins-det↗