arXiv subjects

Michele Gozzelino

Publications and source records attributed to Michele Gozzelino.

7 recordsLinked to original sources

arXiv2026

A High-frequency Geodetic VLBI Experiment for Optical Clock Comparison

An intercontinental metrological clock comparison between Italy and the Republic of Korea was performed by means of geodetic K-band VLBI observations. The comparison involved the hydrogen masers (H-masers) used at Medicina and Sejong radio telescopes. The same clocks were simultaneously compared by a satellite link and by high-precision optical clocks maintained at the National Metrology Institutes, KRISS in Korea and INRIM in Italy, and delivered to VLBI antennas via optical fiber. The H-masers frequency difference was estimated by extrapolating the clock rate from VLBI data using two geodetic VLBI software. This was subsequently compared with clock differences derived by satellite link and by local optical clocks. Results obtained with different approaches were in agreement at the level of $10^{-15}$ s/s. This pilot study demonstrates that standard high-frequency (K-band) geodetic VLBI campaigns could be a viable approach to conduct intercontinental clock comparisons, now only possible via satellite links. This uncertainty can be reduced thanks to the planned installation of new-generation, broadband, high-frequency receivers on the involved telescopes. K/Q/W-band geodetic observations will allow an improvement of the accuracy of the resulting group delays through broad bandwidth synthesis from 20 to 100 GHz. Furthermore, the Frequency Phase Transfer (FPT) method will also be explored together with the use of PCAL systems installed at the radio telescopes to improve phase stability and thus allow a better estimation of the station clock parameters.

astro-ph.IM↗

arXiv2024

Laser Frequency Stabilization Using Light Shift in Compact Atomic Clocks

This paper describes the Light-Shift Laser-Lock (LSLL) technique, a novel method intended for compact atomic clocks that greatly simplifies the laser setup by stabilizing the pumping-laser frequency to the atoms involved in the clock, without the need of an external reference. By alternating two clock sequences with different light shifts, the method estimates and cancels out a controlled amount of induced light shift, acting on the laser frequency. The LSLL technique is compatible with state-of-the-art 3-level clocks and was demonstrated with FPGA-based electronics on a pulsed-optically-pumped (POP) vapor-cell clock developed at INRIM. The results have shown that the LSLL technique operates robustly, having a capture range of gigahertz without significantly compromising clock stability. In our tests, the clock exhibited a white frequency noise of $3.2 \times 10^{-13}$ $τ^{-1/2}$ for averaging time up to 4000 s, reaching a floor below $1 \times 10^{-14}$ up to 100 000 s. These performance levels meet the requirements of future Global Navigation Satellite Systems (GNSS) on-board clocks, and offer the added benefits of a reduced clock footprint, as well as increased reliability and robustness.

physics.atom-ph↗

arXiv2023

A pulsed optically pumped Rb clock with a frequency stability below 10-15

We present the frequency stability performances of a vapor cell Rb clock based on the pulsed optically pumping (POP) technique. The clock has been developed in the frame of a collaboration between INRIM and Leonardo SpA, aiming to realize a space-qualified POP frequency standard. The results here reported were obtained with an engineered physics package, specifically designed for space applications, joint to laboratory-grade optics and electronics. The measured frequency stability expressed in terms of Allan deviation is $1.2 \times 10^{-13}$ at 1 s and achieves the value of $6 \times 10^{-16}$ for integration times of 40000 s (drift removed). This is, to our knowledge, a record result for a vapor-cell frequency standard. In the paper, we show that in order to get this result, a careful stabilization of microwave and laser pulses is required.

physics.atom-ph↗

arXiv2022

Absolute frequency measurement of a Yb optical clock at the limit of the Cs fountain

We present the new absolute frequency measurement of ytterbium (171Yb) obtained at INRiM with the optical lattice clock IT-Yb1 against the cryogenic caesium (133Cs) fountain IT-CsF2, evaluated through a measurement campaign that lasted 14 months. Measurements are performed by either using a hydrogen maser as a transfer oscillator or by synthesizing a low-noise microwave for Cs interrogation using an optical frequency comb. The frequency of the 171Yb unperturbed clock transition 1S0 - 3P0 results to be 518 295 836 590 863.44(14) Hz, with a total fractional uncertainty of 2.7e-16 that is limited by the uncertainty of IT-CsF2. Our measurement is in agreement with the Yb frequency recommended by the Consultative Committee for Time and Frequency (CCTF). This result confirms the reliability of Yb as a secondary representation of the second and is relevant to the process of redefining the second in the International System of Units (SI) on an optical transition

physics.atom-ph↗

arXiv2022

Frequency noise characterization of diode lasers for vapor cell clocks applications

The knowledge of the frequency noise spectrum of a diode laser is of interest in several high resolution experiments. Specifically, in laser-pumped vapor cell clocks, it is well established that the laser frequency noise plays a role in affecting the clock performances. It is then important to characterize the frequency noise of a diode laser, especially since such measurements are rarely found in the literature and hardly ever provided by vendors. In this paper, we describe a technique based on a frequency-to-voltage converter that transforms the laser frequency fluctuations into voltage fluctuations. In this way, it is possible to characterize the laser frequency noise power spectral density in a wide range of Fourier frequencies, as required in cell clock applications.

physics.atom-ph↗

arXiv2020

Loaded microwave cavity for compact vapor-cell clocks

Vapor-cell devices based on microwave interrogation provide a stable frequency reference with a compact and robust setup. Further miniaturization must focus on optimizing the physics package, containing the microwave cavity and atomic reservoir. In this paper we present a compact cavity-cell assembly based on a dielectric-loaded cylindrical resonator. The structure accommodates a clock cell with $0.9 \, \mathrm{cm^3}$ inner volume and has an outer volume of only $35 \, \mathrm{cm^3}$. The proposed design aims at strongly reducing the core of the atomic clock, maintaining at the same time high-performing short-term stability ($σ_y(τ) \leq 5\times 10^{-13} \,τ^{-1/2}$ standard Allan deviation). The proposed structure is characterized in terms of magnetic field uniformity and atom-field coupling with the aid of finite-elements calculations. The thermal sensitivity is also analyzed and experimentally characterized. We present preliminary spectroscopy results by integrating the compact cavity within a rubidium clock setup based on the pulsed optically pumping technique. The obtained clock signals are compatible with the targeted performances. The loaded-cavity approach is thus a viable design option for miniaturized microwave clocks.

physics.atom-ph↗

arXiv2018

Reducing cavity-pulling shift in Ramsey-operated compact clocks

We describe a method to stabilize the amplitude of the interrogating microwave field in compact atomic clocks working in a Ramsey approach. In this technique, we take advantage of the pulsed regime to use the atoms themselves as microwave amplitude discriminators. Specifically, in addition to the dependence on the microwave detuning, the atomic signal after the Ramsey interrogation acquires a dependence on the microwave pulse area (amplitude times duration) that can be exploited to implement an active stabilization of the microwave field amplitude, in a similar way in which the Ramsey clock signal is used to lock the local oscillator frequency to the atomic reference. This stabilization results in a reduced sensitivity of the clock frequency to microwave amplitude fluctuations that are transferred to the atoms through the cavity-pulling effect. The proposed technique is then effective to improve the clock stability and drift on medium and long term. We demonstrate the method for a vapor-cell clock working with a hot sample of atoms but it can be extended to cold-atom compact clocks.

physics.atom-ph↗