arXiv subjects

Sarah K. Scholten

Publications and source records attributed to Sarah K. Scholten.

4 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↗

arXiv2026

Ultra-high precision speckle spectrometer enabling radio-frequency scale resolution of atomic spectra

Laser speckle, the granular intensity pattern arising from random optical interference, provides a high-dimensional encoding of spectral information that can be exploited for precision metrology. Speckle-based spectrometers have advanced rapidly owing to their compact footprint, mechanical robustness and alignment agnostic nature, yet their spectral resolution has remained limited to the picometre scale. In this work, we break this limit by employing an integrating sphere as a multiply scattering cavity with access to a high range of path lengths to enhance spectral sensitivity. At 780$\,$nm, the resulting device achieves a resolution of 6$\,$fm, corresponding to a resolving power of $1.3\times10^8$, representing an approximately 80-fold improvement over previous implementations. This ultra-high resolution enables clear discrimination of laser sidebands generated by an electro-optical modulator, with extracted sideband powers agreeing with expected values to within 1%. It further permits the first direct speckle-based measurement of the hyperfine structure of the $\text{D}_{2}$ transition in $^{85}\text{Rb}$, with transmission spectra differing by no more than 3.6% from independent wavemeter-referenced measurements. These results establish speckle as a new platform for ultra-high precision spectroscopy, radio-frequency spectrometry, and microwave photonics.

physics.optics↗

arXiv2024

Tailoring the Stability of a Two-Color, Two-Photon Rubidium Frequency Standard

Rubidium two-photon frequency standards are emerging as powerful contenders for compact, durable devices with exceptional stability. The field has focused on single-color excitation to date. Here we demonstrate the key advantages of a two-color excitation of a two-photon optical frequency standard based on the $5S_{1/2}\,{\rightarrow}\,5D_{5/2}$ transition of rubidium-87 utilising driving fields at 780 nm and 776 nm. We show that utilising the $5P_{3/2}$ intermediate state to resonantly enhance the transition, we can for the first time attain frequency stabilities comparable to the rubidium single-color two-photon frequency standards, notably with approximately ten-fold less optical power and ten-fold lower rubidium vapor density. Optimisation of the detuning from the $5P_{3/2}$ intermediate state, and optical powers of driving lasers, has a dramatic effect on the frequency stability, achieving the best short-term stability of any two-photon rubidium frequency standard to date, of $6{\times}10^{-14}$ at $τ$ = 1 s. We demonstrate this level of performance is compatible with a compact geometry, by fully self-referencing the frequency standard using an integrated fiber frequency comb to simultaneously stabilize the 780 nm laser's detuning from the $5P_{3/2}$ intermediate state, and produce a frequency-stable microwave output. A comprehensive noise characterization underpins our observations of this two-color frequency standard which explains the measured stability, showing this frequency standard is shot-noise limited initially before becoming limited by light shifts in the long-term. This work represents a major advance towards a low size, weight, and power frequency standard based on this two-color excitation method.

physics.atom-ph↗

arXiv2022

Experimental and theoretical study of dynamic polarizabilities in the $5S_{1/2}$-$5D_{5/2}$ clock transition in rubidium-87 and determination of E1 matrix elements

The interaction between light and an atom causes perturbations in the atom's energy levels, known as the light-shift. These light-shifts are a key source of inaccuracy in atomic clocks, and can also deteriorate their precision. We present a study of light-shifts and associated dynamic polarizabilities for a two-photon atomic clock based on the $5S_{1/2}$-$5D_{5/2}$ transition in rubidium-87 over the range 770 nm to 800 nm. We determine experimental and theoretical values for a magic wavelength in this range and the electric dipole (E1) matrix element for the $5P_{3/2}$-$5D_{5/2}$ transition. We find a magic wavelength of 776.179(5) nm (experimental) and 776.21 nm (theoretical) in the vicinity of the $5P_{3/2}$-$5D_{5/2}$ resonance, and the corresponding reduced E1 matrix element 1.80(6) $ea_0$ (experimental) and 1.96(15) $ea_0$ (theoretical). These values resolve a previous discrepancy between theory and experiment.

physics.atom-ph↗