arXiv subjects

Warwick P Bowen

Publications and source records attributed to Warwick P Bowen.

5 recordsLinked to original sources

arXiv2026

Sub-microsecond conformational dynamics in an optical nanocavity

Microsecond conformational changes underlie many protein functions, but ensemble averaging has been needed to observe them without labels. Single-shot measurements on individual proteins have had insufficient speed, while protein Brownian-motion has obscured signals. Here, we report a fibre-integrated silicon-photonic sensor that overcomes these barriers, resolving protein dynamics at sub-microsecond speeds in continuous single-shot measurements that can extend over minutes. This is achieved by combining far-sub-wavelength optical field confinement with high optical field uniformity that suppresses protein Brownian-motion by a factor of sixty. In single-shot measurements on ferritin molecules, we observe tens of thousands of transitions consistent with conformational fluctuations of the ferritin shell, resolving them over timescales as short as 400 ns. The ability to continuously monitor transitions over long times reveals switching kinetics, memory effects and molecular heterogeneity hidden in ensemble averages. This opens a new path to improved mechanistic understanding of protein function.

physics.optics↗

arXiv2022

Roadmap for Optical Tweezers

Optical tweezers are tools made of light that enable contactless pushing, trapping, and manipulation of objects ranging from atoms to space light sails. Since the pioneering work by Arthur Ashkin in the 1970s, optical tweezers have evolved into sophisticated instruments and have been employed in a broad range of applications in life sciences, physics, and engineering. These include accurate force and torque measurement at the femtonewton level, microrheology of complex fluids, single micro- and nanoparticle spectroscopy, single-cell analysis, and statistical-physics experiments. This roadmap provides insights into current investigations involving optical forces and optical tweezers from their theoretical foundations to designs and setups. It also offers perspectives for applications to a wide range of research fields, from biophysics to space exploration.

physics.optics↗

arXiv2021

Enhanced optical trapping via structured scattering

Interferometry can completely redirect light, providing the potential for strong and controllable optical forces. However, small particles do not naturally act like interferometric beamsplitters, and the optical scattering from them is not generally thought to allow efficient interference. Instead, optical trapping is typically achieved via deflection of the incident field. Here we show that a suitably structured incident field can achieve beamsplitter-like interactions with scattering particles. The resulting trap offers order-of-magnitude higher stiffness than the usual Gaussian trap in one axis, even when constrained to phase-only structuring. We demonstrate trapping of 3.5 to 10.0~$μ$m silica spheres, achieving stiffness up to 27.5$\pm$4.1 times higher than is possible using Gaussian traps, and two orders of magnitude higher measurement signal-to-noise ratio. These results are highly relevant to many applications, including cellular manipulation, fluid dynamics, micro-robotics, and tests of fundamental physics.

physics.optics↗

arXiv2014

Coherent control and feedback cooling in a remotely-coupled hybrid atom-optomechanical system

Cooling to the motional ground state is an important first step in the preparation of nonclassical states of mesoscopic mechanical oscillators. Light-mediated coupling to a remote atomic ensemble has been proposed as a method to reach the ground state for low frequency oscillators. The ground state can also be reached using optical measurement followed by feedback control. Here we investigate the possibility of enhanced cooling by combining these two approaches. The combination, in general, outperforms either individual technique, though atomic ensemble-based cooling and feedback cooling each individually dominate over large regions of parameter space.

quant-ph↗

arXiv2013

Optical lock-in particle tracking in optical tweezers

We demonstrate a lock-in particle tracking scheme in optical tweezers based on stroboscopic modulation of an illuminating optical field. This scheme is found to evade low frequency noise sources while otherwise producing an equivalent position measurement to continuous measurement. This was demonstrated, and found to yield on average 20dB of noise suppression in the frequency range 10-5000 Hz, where low frequency laser noise and electronic noise was significant, and 35 dB of noise suppression in the range 550-710 kHz where laser relaxation oscillations introduced laser noise. The setup is simple, and compatible with any trapping optics.

physics.optics↗