arXiv subjects

Rachel F. Offer

Publications and source records attributed to Rachel F. Offer.

7 recordsLinked to original sources

arXiv2026

A Portable Dual-Color Two-Photon Rubidium Optical Frequency Standard

Portable atomic clocks are essential in a wide variety of applications, most notably in the operation of global navigation satellite systems. Existing portable atomic clocks utilizing microwave-based interrogation schemes are now routinely eclipsed by the next generation of atomic frequency standards based on optical interrogation. While optical frequency standards demonstrate greatly improved frequency stability, they have only recently reached a level of technical maturity required to demonstrate this improved performance outside of well curated laboratory environments. Here, we demonstrate a fully autonomous and portable optical frequency standard based on an efficient dual-color excitation of the $5S_{1/2}\rightarrow5D_{5/2}$ two-photon transition in $^{87}$Rb. The standard utilizes a combination of robust, highly developed commercial-off-the-shelf telecommunications technologies and a fully integrated portable optical frequency comb, providing the optical and microwave outputs vital for interfacing with existing electronic systems and infrastructure. The system demonstrates a fractional frequency stability of $1.9\times10^{-13}$ at 1s of integration time, reaching $3.5\times10^{-15}$ at 8000s of integration time without the need for drift removal. This portable demonstrator unit marks a significant achievement in the development of Rb optical atomic frequency standards, and for the deployment of optical atomic frequency standards outside of the laboratory.

physics.atom-ph↗

arXiv2025

Demonstration of a simple and compact ytterbium magneto-optical trap

We present a low Size, Weight and Power (SWaP), low-complexity, ytterbium magneto-optical trap (MOT). We demonstrate trapping of $1.4 \times 10^6$ $^{171}$Yb atoms on the $|{^1S_0}, F = 1/2\rangle \leftrightarrow |{^1P_1}, F' = 3/2\rangle$ transition directly from a hot thermal beam. We explore the effect of trap detuning and oven temperature on trap number, density, loading rate and sample temperature. The low SWaP and low-complexity design presents a realistic pathway towards portable ytterbium MOTs, allowing cold atom ytterbium systems to escape the confines of the laboratory and perform precision measurements in field environments.

physics.atom-ph↗

arXiv2024

Characterization of near-infrared to telecom frequency conversion in a rubidium-filled hollow-core photonic-crystal fiber

We investigate near-infrared to telecommunications frequency conversion via a diamond four-wave mixing scheme in rubidium vapor contained within a hollow-core photonic-crystal fiber. The strong light-atom interaction in the fiber results in lower pump power requirements and higher conversion efficiency than can be achieved under equivalent conditions in a rubidium vapor cell. We also observe non-intuitive pump and signal frequency dependence of the four-wave mixing efficiency in the fiber due to the large nonlinearities present in the system. These results indicate the potential for hollow-core fibers to provide a scalable solution to quantum information network infrastructure, with additional modelling required for a full understanding of the extreme atom-light interaction effects present.

physics.atom-ph↗

arXiv2021

A simple, powerful diode laser system for atomic physics

External-cavity diode lasers are ubiquitous in atomic physics and a wide variety of other scientific disciplines, due to their excellent affordability, coherence length and versatility. However, for higher power applications, the combination of seed lasers, injection-locking and amplifiers can rapidly become expensive and complex. Here we present a useful, high-power, single-diode laser design with specifications: $>210\,$mW, $100\,$ms-linewidth ($427 \pm 7$) kHz, $>99\%$ mode purity, $10\,$GHz mode-hop-free tuning range and $12\,$nm coarse tuning. Simple methods are outlined to determine the spectral purity and linewidth with minimal additional infrastructure. The laser has sufficient power to collect $10^{10}$ $^{87}$Rb atoms in a single-chamber vapour-loaded magneto-optical trap. With appropriate diodes and feedback, the system could be easily adapted to other atomic species and laser formats.

physics.ins-det↗

arXiv2021

Gouy phase-matched angular and radial mode conversion in four-wave mixing

Studying the conversion between transverse light modes via four-wave mixing in a heated rubidium vapour, we demonstrate and explain a transfer between azimuthal and radial mode numbers. These relate to orthogonal modal dimensions, which one would not normally expect to interact. While angular momentum conservation in this nonlinear process dictates the selection rules for the angular mode number, the role of the radial mode number is more esoteric. We demonstrate systematically that the Gouy phase is the key to understanding this conversion, leading to strikingly different conversion behaviour in the thick and thin medium regime. Our experimental investigation of the transition between these regimes bridges the gap between previous experiments in atomic thick media and work in nonlinear crystals. Our work sets a clear starting point to explore new territory in the thick medium regime, allowing efficient radial-to-azimuthal and radial-to-radial mode conversion.

physics.atom-ph↗

arXiv2018

Spiral bandwidth of four-wave mixing in Rb vapour

Laguerre-Gauss beams, and more generally the orbital angular momentum of light (OAM) provide valuable research tools for optical manipulation, processing, imaging and communication. Here we explore the high-efficiency frequency conversion of OAM in a four-wave mixing process in rubidium vapour. Conservation of the OAM in the two pump beams determines the total OAM shared by the generated light fields at 420 nm and 5.2 um - but not its distribution between them. We experimentally investigate the spiral bandwidth of the generated light modes as a function of pump OAM. A small pump OAM is transferred almost completely to the 420 nm beam. Increasing the total pump OAM broadens the OAM spectrum of the generated light, indicating OAM entanglement between the generated light fields. This clears the path to high-efficiency OAM entanglement between widely disparate wavelengths.

physics.atom-ph↗

arXiv2016

Cavity-enhanced frequency up-conversion in rubidium vapour

We report the first use of a ring cavity to both enhance the output power and dramatically narrow the linewidth ($<1\,$MHz) of blue light generated by four wave mixing in a rubidium vapour cell. We find that the high output power available in our cavity-free system leads to power broadening of the generated blue light linewidth. Our ring cavity removes this limitation, allowing high output power and narrow linewidth to be achieved concurrently. As the cavity blue light is widely tunable over the $^{85}$Rb 5S$_{1/2} \,\,F=3$ $\rightarrow$ 6P$_{3/2}$ transition, this narrow linewidth light would be suitable for second-stage laser cooling, which could be valuable for efficient $^{85}$Rb BEC production.

physics.atom-ph↗