arXiv subjects

D. J. Brown

Publications and source records attributed to D. J. Brown.

4 recordsLinked to original sources

arXiv2026

Robust watt-level continuous-wave deep-ultraviolet lasers near 230 nm

Continuous-wave (CW) deep-ultraviolet (DUV) lasers near 230~nm enable laser cooling of AlF, Cd, and Zn, but second-harmonic generation below 237~nm relies in practice on beta-barium borate (BBO), whose walk-off and UV-induced degradation hinder sustained operation. We demonstrate compact, affordable VECSEL-based systems informed by four years of operating 14 DUV cavities in 12 laser systems across six European laboratories. External LBO cavities produce nearly 4~W at 463~nm with 94% cavity efficiency. We compare spherically and elliptically focused Brewster-cut BBO cavities with a normal-incidence AR-coated design. The AR-coated cavity delivers the highest power and efficiency, reaching 1.0~W at 51% cavity and 44% external efficiency; the spherical Brewster cavity reaches 700~mW and maintains constant circulating power over 70~h, while elliptical focusing reduces peak intensity sixfold and improves beam quality, albeit with greater alignment sensitivity. Collaboration-designed DUV optics, AlF spectroscopy, and Cd trapping validate the system.

physics.atom-ph↗

arXiv2022

Thermalization in a Spin-Orbit coupled Bose gas by enhanced spin Coulomb drag

An important component of the structure of the atom, the effects of spin-orbit coupling are present in many sub-fields of physics. Most of these effects are present continuously. We present a detailed study of the dynamics of changing the spin-orbit coupling in an ultra-cold Bose gas, coupling the motion of the atoms to their spin. We find that the spin-orbit coupling greatly increases the damping towards equilibrium. We interpret this damping as spin drag, which is enhanced by spin-orbit coupling rate, scaled by a remarkable factor of $8.9(6)$~s. We also find that spin-orbit coupling lowers the final temperature of the Bose gas after thermalization.

cond-mat.quant-gas↗

arXiv2018

A versatile apparatus for two-dimensional atomtronic quantum simulation

We report on the implementation of a novel optical setup for generating high-resolution customizable potentials to address ultracold bosonic atoms in two dimensions. Two key features are developed for this purpose. The customizable potential is produced with a direct image of a spatial light modulator, conducted with an in-vacuum imaging system of high numerical aperture. Custom potentials are drawn over an area of 600 $\times$ 400 μm with a resolution of 0.9 μm. The second development is a two-dimensional planar trap for atoms with an aspect ratio of 900 and spatial extent of Rayleigh range 1.6 $\times$ 1.6 mm, providing near-ballistic in-planar movement. We characterize the setup and present a brief catalog of experiments to highlight the versatility of the system.

quant-ph↗

arXiv2018

Thermalization, condensate growth, and defect formation in an out-of-equilibrium Bose gas

We experimentally and numerically investigate thermalization processes of a trapped $^{87}$Rb Bose gas, initially prepared in a non-equilibrium state through partial Bragg diffraction of a Bose-Einstein condensate (BEC). The system evolves in a Gaussian potential, where we observe the destruction of the BEC due to collisions, and subsequent growth of a new condensed fraction in an oscillating reference frame. Furthermore, we occasionally observe the presence of defects, which we identify as gray solitons. We simulate the evolution of our system using the truncated Wigner method and compare the outcomes with our experimental results.

cond-mat.quant-gas↗