AMO Parallel Talks

Optical transitions in highly charged ions (HCIs) are promising candidates for high-accuracy atomic clocks due to predicted reduced sensitivity to external perturbations and can further be used to investigate beyond Standard Model physics. Various HCIs, such as Ar13+, have been identified as having enhanced sensitivity to potential time variations in the fine structure constant. In this presentation, successful production of HCIs is demonstrated using a compact electron beam ion trap (EBIT), along with successful trapping of Be+ in a cryogenic radiofrequency (rf) Paul trap. Elements of the beamline, including steering, selection, and deceleration used for the transportation of HCIs into the trapping region, are presented. In future work, a single Be+ “logic” ion will be co-trapped with an HCI “clock” ion for sympathetic cooling, quantum-logic spectroscopy (QLS), and state readout operations.

Ultracold quantum gases of polar molecules provide powerful platforms for studying exotic many-body quantum phenomena due to their large electric dipole moments and vast local Hilbert spaces [1, 2]. Such experiments require well-stabilized lasers for cooling, trapping, detection, and high-fidelity manipulation of molecular quantum states. However, spatially varying differential AC Stark shifts arising from optical traps can limit rotational coherence and hinder studies of quantum phases and dynamics.

Here, we demonstrate techniques for characterizing, stabilizing, and spectrally filtering lasers used in ultracold molecule experiments. We measure and compare laser linewidths using two methods: a self-heterodyne interferometer, and a scanning Fabry-Pérot cavity. Finally, we present a filter-cavity design intended to enhance the spectral purity of a magic-wavelength optical trap for KRb molecules; such a trap will maintain a zero differential energy shift for the two relevant rotational states and has been realized for ⁸⁷Rb¹³³Cs [3] and ²³Na⁴⁰K [4]. This trap is expected to enable second-scale rotational coherence times, supporting future studies of many-body spin dynamics with ultracold molecules.

[1] A. N. Carroll, et al., Science 388, 6745 (2025)

[2] C. Miller, et al., Nature 633, 332–337 (2024)

[3] P.D. Gregory, et al., Nature Physics 20, 415-421 (2024)

[4] R. Bause, et al., PRL 125, 023201 (2020)"

Vanadium dioxide (VO₂) is an opaque phase change material that undergoes an ultrafast, insulator-to-metal phase transition near room temperature, making it a promising material for next-generation computing [1,2]. Visible time-domain Brillouin scattering (TDBS) has previously enabled nondestructive extraction of elastic and structural properties in nanoscale transparent materials [3]; here, we demonstrate the first tabletop EUV-TDBS experiment, extending this approach to opaque materials by studying a ~100 nm thick VO₂ thin film with high surface roughness.

An ultrafast infrared pump pulse impulsively heats the VO₂ film, launching a longitudinal acoustic pulse. High harmonic generation produces an ultrafast EUV harmonic comb [5] to stroboscopically probe the acoustic-pulse-induced change in reflectivity. Reflected harmonics are spectrally separated, enabling simultaneous detection at each photon energy [4].

The resulting reflectivity signal exhibits chirped oscillations due to interference between the EUV light reflected from the surface and from the acoustic pulse within the film, with the oscillation frequency increasing with probe photon energy. We fit this dispersion to an analytical Brillouin-scattering model for absorbing media to extract the film's longitudinal acoustic velocity. To explain the surprising persistence and amplitude of the oscillations despite strong EUV absorption, we also model the nanostructured film as a periodic VO₂ grating using rigorous coupled-wave analysis [6], which qualitatively reproduces this behavior. The extracted acoustic velocity (~2263 m/s) is substantially reduced relative to bulk VO₂, as expected for a nanostructured thin film.

[1] Jager et al., PNAS 114 (36), 9558 (2017) 

[2] Lysenko et al., Phys, Rev. B 82 (20), 205425 (2010)

[3] Gusev and Ruello, Appl. Phys. Rev. 5 (3), 031101 (2018)

[4] Johnsen et al., Rev. Sci. Instrum. 94 (3), 033001 (2023)

[5] Rundquist et al., Science, 280 (5368), 1412 (1998)

[6] Hugonin and Lalanne, arXiv:2101.00901

Efficient and stable optical fiber coupling is critical in precision laser optics, atomic physics, and quantum information experiments. However, manual alignment of laser to fiber interfaces remains highly sensitive to thermal drift, mechanical relaxation, and manual error. We present the design, algorithmic framework, and experimental characterization of a compact, automated optical alignment system. Utilizing a closed loop feedback architecture driven by active photodiode sensing and motorized kinematic mounts, the auto-aligner dynamically optimizes fiber coupling across dual tilt-and-translation axes. Experimental characterization demonstrates fast recovery from mechanical drift and sustained high efficiency coupling over extended continuous operation. This framework provides a scalable, low-cost solution for reducing system downtime and maintaining stability in complex laser setups

Fabry–Pérot etalons provide accessible, high-stability wavelength calibration across hundreds of nanometers for astronomical spectrographs used in exoplanet discovery and characterization. However, the multilayer dielectric mirror coatings can cause shifts in cavity modes across the bandwidth, limiting calibration precision. To improve etalon performance, we use the transfer-matrix method for computational modeling and genetic algorithms to optimize SiO₂/Nb₂O₅ mirror coatings. By tuning individual layer thicknesses, we aim to reduce mode drift while controlling broadband reflectivity and phase response. This work supports the development of compact, cost-effective calibration sources that can improve the stability and accuracy of precision radial velocity measurements.

Optical tweezers use highly focused laser beams to trap and manipulate microscopic particles. They gained widespread recognition through the 2018 Nobel Prize in Physics and are now important tools in fields ranging from biophysics to precision measurement. Particles in deep optical traps can often be modeled as harmonic oscillators, but increasing trap depth also increases noise from the trapping laser. Shallower traps reduce this noise but become increasingly anharmonic, requiring a description beyond the harmonic approximation. Here, we use numerical simulations of Brownian motion in anharmonic optical traps to investigate whether noise and anharmonicity can work together to improve particle confinement.

This summer, I worked on several experimental systems for measuring the optical and surface properties of nanoscale materials in the Raschke research group. One project focused on samples produced by Angstrom Engineering, where I used tapping-mode atomic force microscopy to measure surface roughness and compare different substrates, coating thicknesses, and adhesion layers. I also built and assembled a micro-FTIR spectroscopy system, establishing the optical path and integrating the microscope and spectrometer components needed for infrared measurements. Another major effort involved rebuilding and characterizing a partially disassembled Renishaw inVia Raman spectrometer, including developing a fiber-coupled input path and testing the system using a silicon Raman signal. Finally, I developed the optical layout for a cryogenic Raman setup based on an inverted microscope, including beam routing, filtering, and spectrometer coupling. Together, these projects combined instrument construction, optical alignment, spectroscopy, and nanoscale surface characterization to expand the laboratory’s experimental capabilities.

Ultrafast structural dynamics creates a window to the fundamental processes that govern chemical reactions; however, directly observing atomic motion is difficult. This project combines both experiments with computational modeling. I aim to combine X-ray liquidography with molecular dynamics (MD) simulations to investigate the structural response of molecules in solvent following rapid excitation. Experimentally, a stable liquid sheet jet delivery system was developed to produce thin (90-200 micrometers thick), continuously refreshed sample sheets for pump-probe measurements using a compact X-ray light source. Time-resolved scattering patterns were collected to probe structural evolution on the femto to picosecond timescale. Complementing these measurements, molecular dynamic simulations of water with NaI and diiodomethane (CH2I2), along with cyclohexane with iodoethane (C2H5I) and iodopropane (C3H7I) were performed using GROMACS to model equilibrium and non-equilibrium—determined by DFT calculations using Gaussian—behavior. Simulated trajectories were analyzed to calculate small-angle X-ray scattering (SAXS) profiles and transformed into real space correlation functions to allow for direct comparison to experimental data. By integrating advanced computational modeling with ultrafast scattering experiments, this work establishes a framework for interpreting structural changes and atomic scale molecular dynamics with experimentally observable X-ray scattering signals.