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Compact Transportable Optical Standard Based on a Single 171Yb+ Ion (“YBIS” Project)
摘要： The schematic diagram of the compact transportable optical frequency standard based on the quadrupole transition in a single 171Yb+ ion with a relative instability at the level of 5 · 10?16, less than 1 m3 in volume and less than 300 kg in weight is presented. The ionic trap and laser systems are described. Trapping and laser cooling of the 174Yb+ ion are experimentally demonstrated.
关键词： ytterbium ion,transportable frequency standard,optical clock
更新于2025-09-23 15:23:52
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from Isotope and Isomer Shifts
摘要： The isotope 229Th is unique in that it possesses an isomeric state of only a few electron volts above the ground state, suitable for nuclear laser excitation. An optical clock based on this transition is expected to be a very sensitive probe for variations of fundamental constants, but the nuclear properties of both states have to be determined precisely to derive the actual sensitivity. We carry out isotope shift calculations in Tht and Th2t including the specific mass shift, using a combination of configuration interaction and all-order linearized coupled-cluster methods and estimate the uncertainty of this approach. We perform experimental measurements of the hyperfine structure of Th2t and isotopic shift between 229Th2t and 232Th2t to extract the difference in root-mean-square radii as δhr2i232;229 ? 0.299e15T fm2. Using the recently measured values of the isomer shift of lines of 229mTh, we derive the value for the mean-square radius change between 229Th and its low-lying isomer 229mTh to be δhr2i229m;229 ? 0.0105e13T fm2.
关键词： optical clock,nuclear charge radii,isomer shift,229Th,isotope shift
更新于2025-09-23 15:21:21
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Ultrastable Laser System for Spectroscopy of the 1.14 μm Inner-Shell Clock Transition in Tm and Its Absolute Frequency Measurement
摘要： We characterize a 1.14 μm ultrastable semiconductor laser system for precision spectroscopy of Tm inner-shell clock transition using a frequency comb. We stabilize both the repetition and the carrier-envelope o?set frequencies of a commercial Ti : sapphire femtosecond laser to a passive hydrogen maser using a home-built f -2f interferometer. By measuring the absolute frequency of the 1.14 μm laser stabilized to a high-?nesse ULE cavity, we determine the zero-expansion temperature point of the cavity and the rate of linear drift of the the cavity resonance frequency due to “aging” of the ULE glass. We achieve less than 10 Hz frequency instability of the laser within 1,000 s after the linear drift compensation. We also measured the absolute frequency of the 1.14 μm transition in Tm to be 262 954 938 269 213(30) Hz.
关键词： thulium,optical clock,frequency comb
更新于2025-09-16 10:30:52
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Development of an Interference Filter-Stabilized External-Cavity Diode Laser for Space Applications
摘要： The National Time Service Center of China is developing a compact, highly stable, 698 nm external-cavity diode laser (ECDL) for dedicated use in a space strontium optical clock. This article presents the optical design, structural design, and preliminary performance of this ECDL. The ECDL uses a narrow-bandwidth interference ?lter for spectral selection and a cat’s-eye re?ector for light feedback. To ensure long-term stable laser operation suitable for space applications, the connections among all the components are rigid and the design avoids any spring-loaded adjustment. The frequency of the ?rst lateral rocking eigenmode is 2316 Hz. The ECDL operates near 698.45 nm, and it has a current-controlled tuning range over 40 GHz and a PZT-controlled tuning range of 3 GHz. The linewidth measured by the heterodyne beating between the ECDL and an ultra-stable laser with 1 Hz linewidth is about 180 kHz. At present, the ECDL has been applied to the principle prototype of the space ultra-stable laser system.
关键词： laser diode,interference ?lter,space optical clock,external-cavity diode laser,laser stabilization
更新于2025-09-16 10:30:52
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Optical Frequency Stabilization at the 10 <sup>?16</sup> Fractional Level Utilizing Ramsey-Borde Atom Interferometry
摘要： We demonstrate laser frequency stabilization at the 10-16 fractional frequency level in one second through spectroscopy on a 650 ?C calcium atomic beam. The calcium beam is interrogated with a cavity stabilized 657 nm laser arranged in a Ramsey-Borde configuration. A second laser at 431 nm reads off the final atomic state populations while allowing for high signal-to-noise. Limitations of this method are being explored and, based on current noise analysis, there is potential to achieve fractional frequency stabilities in the 10-17 range or below.
关键词： calcium,atomic clock,Measurement,stabilized laser,optical clock,Ramsey,Bordé,precision measurements,optical frequency standard
更新于2025-09-10 09:29:36
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Optical Frequency Measurements at 1×10?18 Uncertainty with Ytterbium Optical Lattice Clocks
摘要： We describe ytterbium optical lattice clocks under development at NIST. This includes the characterization of optical frequency stability and uncertainty, as well as measurements between two independent clocks, at the 10-18 level. We also report on optical frequency ratio measurements with other optical clocks at NIST.
关键词： precision frequency,optical lattice,optical standard,ytterbium,frequency measurement,uncertainty,optical ratio,optical clock
更新于2025-09-10 09:29:36