More Like this

1. Prospects of a thousand-ion Sn2+ Coulomb-crystal clock with sub-10^(−19) inaccuracy

   https://doi.org/10.48550/arXiv.2205.15484  

   Leibrandt, D.R. ; Porsev, S.G. ; Cheung, C. ; Safronova, M.S. ( July 2022 , ArXivorg)

   We propose a many-ion optical atomic clock based on three-dimensional Coulomb crystals of order one thousand Sn2+ ions confined in a linear RF Paul trap. Sn2+ has a unique combination of features that is not available in previously considered ions: a 1S0 ↔ 3P0 clock transition between two states with zero electronic and nuclear angular momentum (I = J = F = 0) making it immune to nonscalar perturbations, a negative differential polarizability making it possible to operate the trap in a manner such that the two dominant shifts for three-dimensional ion crystals cancel each other, and a laser-accessible transition suitable for direct laser cooling and state readout. We present analytical calculations of the differential polarizability and other relevant atomic properties, as well as numerical calculations of the motion of ions in large Coulomb crystals, to estimate the achievable accuracy and precision of Sn2+ Coulomb-crystal clocks. 

   more » « less
2. Prolonged Slip on the South Tibetan Detachment Constrains Tectonic Models for Synorogenic Extension in the Central Himalaya

   https://doi.org/10.1029/2022TC007298  

   Pye, Alexandra E. ; Hodges, Kip V. ; Keller, C. Brenhin ; Law, Richard D. ; van Soest, Matthijs C. ; Bhandari, Basant ; McDonald, Christopher S. ( November 2022 , Tectonics)

   The South Tibetan detachment system (STDS) is one of the most important deformational features in the Himalayan orogen; yet its evolution in space and time remain incompletely understood. Here, we present the results of a new study of the primary, basal strand of the STDS in the Annapurna Himalaya of central Nepal: the Annapurna detachment. The original discovery outcrop of this structure in the Kali Gandaki valley reveals that multiple leucogranite bodies are variably deformed by ductile slip on the detachment. New laser‐ablation (U‐Th)/Pb dating of complex monazite suites from these bodies indicates that leucogranites in this outcrop intruded over a period extending from at least 22.76 ± 0.30–14.95 ± 0.78 Ma. Field relationships and microstructures within studied samples show that ductile slip on the Annapurna detachment was active—at least episodically—throughout this period and also continued into the more recent past. Based on cooling history models for the outcrop constrained by⁴⁰Ar/³⁹Ar and (U‐Th)/He data, ductile slip likely continued until at least 12 Ma. These results are at odds with previous inferences that slip on the STDS in central Nepal had ceased by ca. 22 Ma and call into question the popular idea that there was an abrupt geodynamic transition from predominantly N‐S‐directed extension to predominantly E‐W‐directed extension in the central Himalaya in the early Miocene.

    

   more » « less
3. Spectroscopy of the 85 Rb 4 D3/2 state for hyperfine-structure determination

   https://doi.org/10.1088/1367-2630/acf405  

   Duspayev, A. ; Raithel, G. ( September 2023 , New Journal of Physics)

   We report a measurement of the hyperfine-structure constants of the⁸⁵Rb 4$D_{3/2}$state using two-photon optical spectroscopy of the 5$S_{1/2}\to$4$D_{3/2}$transition. The spectra are acquired by measuring the transmission of the low-power 795 nm lower-stage laser beam through a cold-atom sample as a function of laser frequency, with the frequency of the upper-stage, 1476 nm laser fixed. All 4 hyperfine components of the$4D_{3/2}$state are well-resolved in the experimental data. The dominant systematic is the light shift from the 1476 nm laser, which is addressed by extrapolating line positions measured for a set of 1476 nm laser powers to zero laser power. The analysis of our experimental data yields both the magnetic-dipole and electric-quadrupole constants for the⁸⁵Rb 4$D_{3/2}$level, without using earlier hyperfine measurements of other atomic levels. The respective results,$A=$7.419(35) MHz and$B=$4.19(19) MHz, are discussed in context with previous works. Our investigation may be useful for optical atomic clocks for precision metrology and emerging atom-based quantum technologies, all-infrared excitation of Rb Rydberg levels, and molecular physics.

    

   more » « less
4. Silicon nitride stress-optic microresonator modulator for optical control applications

   https://doi.org/10.1364/OE.467721  

   Wang, Jiawei ; Liu, Kaikai ; Harrington, Mark W. ; Rudy, Ryan Q. ; Blumenthal, Daniel J. ( August 2022 , Optics Express)

   Modulation-based control and locking of lasers, filters and other photonic components is a ubiquitous function across many applications that span the visible to infrared (IR), including atomic, molecular and optical (AMO), quantum sciences, fiber communications, metrology, and microwave photonics. Today, modulators used to realize these control functions consist of high-power bulk-optic components for tuning, sideband modulation, and phase and frequency shifting, while providing low optical insertion loss and operation from DC to 10s of MHz. In order to reduce the size, weight and cost of these applications and improve their scalability and reliability, modulation control functions need to be implemented in a low loss, wafer-scale CMOS-compatible photonic integration platform. The silicon nitride integration platform has been successful at realizing extremely low waveguide losses across the visible to infrared and components including high performance lasers, filters, resonators, stabilization cavities, and optical frequency combs. Yet, progress towards implementing low loss, low power modulators in the silicon nitride platform, while maintaining wafer-scale process compatibility has been limited. Here we report a significant advance in integration of a piezo-electric (PZT, lead zirconate titanate) actuated micro-ring modulation in a fully-planar, wafer-scale silicon nitride platform, that maintains low optical loss (0.03 dB/cm in a 625 µm resonator) at 1550 nm, with an order of magnitude increase in bandwidth (DC - 15 MHz 3-dB and DC - 25 MHz 6-dB) and order of magnitude lower power consumption of 20 nW improvement over prior PZT modulators. The modulator provides a >14 dB extinction ratio (ER) and 7.1 million quality-factor (Q) over the entire 4 GHz tuning range, a tuning efficiency of 162 MHz/V, and delivers the linearity required for control applications with 65.1 dB·Hz^2/3and 73.8 dB·Hz^2/3third-order intermodulation distortion (IMD3) spurious free dynamic range (SFDR) at 1 MHz and 10 MHz respectively. We demonstrate two control applications, laser stabilization in a Pound-Drever Hall (PDH) lock loop, reducing laser frequency noise by 40 dB, and as a laser carrier tracking filter. This PZT modulator design can be extended to the visible in the ultra-low loss silicon nitride platform with minor waveguide design changes. This integration of PZT modulation in the ultra-low loss silicon nitride waveguide platform enables modulator control functions in a wide range of visible to IR applications such as atomic and molecular transition locking for cooling, trapping and probing, controllable optical frequency combs, low-power external cavity tunable lasers, quantum computers, sensors and communications, atomic clocks, and tunable ultra-low linewidth lasers and ultra-low phase noise microwave synthesizers.

    

   more » « less
5. UV Study of the Fourth Positive Band System of CO and O i 135.6 nm From Electron Impact on CO and CO 2

   https://doi.org/10.1029/2018JA026308  

   Ajello, J. M. ; Malone, C. P. ; Evans, J. S. ; Holsclaw, G. M. ; Hoskins, A. C. ; Jain, S. K. ; McClintock, W. E. ; Liu, X. ; Veibell, V. ; Deighan, J. ; et al ( April 2019 , Journal of Geophysical Research: Space Physics)

   We have measured the 30 and 100 eV far ultraviolet (FUV) emission cross sections of the optically allowed Fourth Positive Group (4PG) band system (A¹Π → X¹Σ⁺) of CO and the optically forbidden O (⁵S^o → ³P) 135.6 nm atomic transition by electron‐impact‐induced‐fluorescence of CO and CO₂. We present a model excitation cross section from threshold to high energy for theA¹Π state, including cascade by electron impact on CO. TheA¹Π state is perturbed by triplet states leading to an extended FUV glow from electron excitation of CO. We derive a model FUV spectrum of the 4PG band system from dissociative excitation of CO₂, an important process observed on Mars and Venus. Our unique experimental setup consists of a large vacuum chamber housing an electron gun system and the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission Imaging Ultraviolet Spectrograph optical engineering unit, operating in the FUV (110–170 nm). The determination of the total Oi(⁵S^o) at 135.6 nm emission cross section is accomplished by measuring the cylindrical glow pattern of the metastable emission from electron impact by imaging the glow intensity about the electron beam from nominally zero to ~400 mm distance from the electron beam. The study of the glow pattern of Oi(135.6 nm) from dissociative excitation of CO and CO₂indicates that the Oi(⁵S^o) state has a kinetic energy of ~1 eV by modeling the radial glow pattern with the published lifetime of 180 μs for the Oi(⁵S^o) state.

    

   more » « less