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Optical frequency standard with ultra-cold strontium atoms

N. Poli, Robert E. Drullinger, Marco G. Tarallo, Fiodor Sorrentino, M. Prevedelli

Published Jan 1, 2006• 2 citations
OpenAlex

Abstract

We report on our progress toward the realization of an optical frequency standard referenced to strontium intercombination lines. While first frequency measurement of the weakly allowed 1S 0- 3P 1 transition was done with saturation spectroscopy on a thermal beam, we are preparing the experimental setup for high resolution spectroscopy on ultracold atoms of the doubly forbidden 1S 0- 3P 0 line. Our current setup allows the capture more than 10 7 atoms at 1 μK in 500 ms in two stages of magneto-optical trapping. We also demonstrated the dipole trapping of ultracold strontium isotopes for accurate spectroscopy and collisional measurements. A semiconductor laser source at 698 nm has already been locked to a pre-stabilization cavity obtaining a fast linewidth of less than 1 kHz. Second stage stabilization of the clock laser to ultra-high finesse cavity is in development. Recent measurement of elastic and inelastic cross-sections of the two most abundant 88Sr and 86Sr isotopes are also presented.

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As a key component of a strontium based optical clock, we have developed an apparatus which allows laser cooling and trapping of more than 10/sup 7/ /sup 88/Sr atoms to temperatures below 1 /spl mu/K. Using this system, we have performed the first high accuracy measurement of the /sup 88/Sr /sup 1/S/sub 0/-/sup 3/P/sub 1/ clock transition using an ultra-cold sample. Detailed descriptions of both the measurement technique and corresponding systematic uncertainties is provided. In addition, by varying the density of the ultra-cold /sup 88/Sr sample over a range of three orders of magnitude we obtain the first definitive measurement of a density-related frequency shift and linewidth broadening of an optical clock transition in an ultra-cold alkaline earth system. Spectroscopy of the /sub 1/S/sub 0/-/sup 3/P/sub 0/ transition is currently underway using this narrow probe laser and an octave spanning femtosecond laser. Our most recent results are presented. The proposed measurement technique, accuracy, and stability of an optical clock based on the EIT (electromagnetically-induced-transparency) measurement in /sup 88/Sr are described.

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Ultracold 88Sr atoms for an optical lattice clock

Thomas Legero, J. S. Raaj Vellore Winfred, F. Riehle +1 more

This paper reports results of cooling and trapping of88Sr for future use in an optical lattice clock. Strontium atoms are cooled to ultra-cold temperatures using a two-stage cooling process. In the first stage, atoms are captured from a Zeeman-slowed atomic beam and cooled to 2 mK in a magneto optical trap operated on the1So-1P1transition at 461 nm. The second cooling stage utilizes the spin forbidden1So-3P1transition at 689 nm. To reach ultra-cold temperatures, 50 ms of broadband cooling is followed by 28 ms long single frequency cooling. The transfer efficiency from the first to the second cooling stage was measured to be 23%, leaving 7 x 106 atoms at a temperature of 1 muK. The atomic cloud is overlapped with a horizontally oriented 1-D far-off resonance optical dipole trap (FORT) at 813 nm with an effective potential depth of 25 muK. Due to equal light shifts of the1Soand the3P1state simultaneous Doppler cooling during the atom loading into the FORT is possible which leads to a transfer efficiency into the dipole trap of up to 60%.

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Optical lattice clock on bosonic Strontium atoms

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We report on recent realization of an optical lattice clock operating on the1S0-3P0transition in88Sr, at LENS laboratories. The clock transition is excited with the technique of magnetic field-induced spectroscopy. New experimental techniques has also been developed in order to simplifies the clock spectroscopy in Sr atoms. The first new method helps in the first search of the clock transition without the use of extensive frequency metrology hardware and in particular optical frequency combs. This technique exploits a near coincidence in the atomic wavelengths of the1S0-3P0clock and1S0-3P1second stage cooling transitions in Sr, which are only 5 THz far apart. This coincidence enables the use of an optical (transfer) cavity to reference the frequency of the clock transition relative to that of the much stronger cooling transition. Secondly we reduce the complexity of the experimental setup by using only semiconductor laser sources in the apparatus. With this setup, about 10488Sr atoms are trapped in a 1D lattice formed by 200 mW of radiation tuned near the magic wavelength at 813 nm. We will present a first uncertainty budget for our optical lattice clock based on88Sr with particular attention to density dependent collisions, which led to an unexpectedly high signal contrast for long interaction times. In view of an absolute frequency measurement of clock transition we'll also present recent experimental results on optimization of an home made Ti:Sa optical frequency comb. Additionally, we anticipate that the simplification of the experimental setup presented will help address a wider range of applications including those requiring transportable devices. Along these lines we will report progress on the realization of the first transportable Sr optical lattice clock.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jun 1, 2009•1 citation
We report on our progress toward the realization of an optical frequency standard referenced to strontium intercombination lines. While first frequency measurement of the weakly allowed 1S 0- 3P 1 transition was done with saturation spectroscopy on a thermal beam, we are preparing the experimental setup for high resolution spectroscopy on ultracold atoms of the doubly forbidden 1S 0- 3P 0 line. Our current setup allows the capture more than 10 7 atoms at 1 μK in 500 ms in two stages of magneto-optical trapping. We also demonstrated the dipole trapping of ultracold strontium isotopes for accurate spectroscopy and collisional measurements. A semiconductor laser source at 698 nm has already been locked to a pre-stabilization cavity obtaining a fast linewidth of less than 1 kHz. Second stage stabilization of the clock laser to ultra-high finesse cavity is in development. Recent measurement of elastic and inelastic cross-sections of the two most abundant 88Sr and 86Sr isotopes are also presented.
We report on our progress toward the realization of an optical frequency standard referenced to strontium intercombination lines. Our current setup allows the production of ultracold Sr atoms in hundreds of ms. For high resolution spectroscopy of1S0-3P0doubly forbidden transition we have also prepared a 698 nm clock laser stabilized on high finesse symmetrically suspended cavity and a high power 813 nm light source for the optical lattice trap at the magic wavelength. All the laser source employed are based on semiconductor device. This opens the way to the realization of compact, reliable and eventually transportable optical frequency standards.
We report on our progress toward the realization of a compact optical frequency standard referenced to strontium intercombination lines. Our current setup allows the production of ultracold Sr atoms in hundreds of ms. For high resolution spectroscopy of the 1S0-3P0 doubly forbidden transition we have prepared a 698 nm clock laser stabilized on a high finesse, symmetrically suspended cavity and a high power 813 nm light source for the optical lattice trap at the magic wavelength. Due to their compactness, reliability, and low power consumption, semiconductor laser sources represent the best choice for the development of compact and transportable devices for application both on Earth and in Space. A new Sr trapping and cooling experimental setup is also presented.
Abstract This report concerns the experiment of precision spectroscopy of cold strontium atoms in the Polish National Laboratory of Atomic, Molecular and Optical Physics in Toruń. The system is composed of a Zeeman slower and magneto-optical traps (at 461 nm and 689 nm), a frequency comb, and a narrow-band laser locked to an ultra-stable optical cavity. All parts of the experiment are prepared and the first measurements of the absolute frequency of the 1S0-3P1, 689 nm optical transition in 88Sr atoms are performed.
As a key component of a strontium based optical clock, we have developed an apparatus which allows laser cooling and trapping of more than 10/sup 7/ /sup 88/Sr atoms to temperatures below 1 /spl mu/K. Using this system, we have performed the first high accuracy measurement of the /sup 88/Sr /sup 1/S/sub 0/-/sup 3/P/sub 1/ clock transition using an ultra-cold sample. Detailed descriptions of both the measurement technique and corresponding systematic uncertainties is provided. In addition, by varying the density of the ultra-cold /sup 88/Sr sample over a range of three orders of magnitude we obtain the first definitive measurement of a density-related frequency shift and linewidth broadening of an optical clock transition in an ultra-cold alkaline earth system. Spectroscopy of the /sub 1/S/sub 0/-/sup 3/P/sub 0/ transition is currently underway using this narrow probe laser and an octave spanning femtosecond laser. Our most recent results are presented. The proposed measurement technique, accuracy, and stability of an optical clock based on the EIT (electromagnetically-induced-transparency) measurement in /sup 88/Sr are described.
This paper reports results of cooling and trapping of88Sr for future use in an optical lattice clock. Strontium atoms are cooled to ultra-cold temperatures using a two-stage cooling process. In the first stage, atoms are captured from a Zeeman-slowed atomic beam and cooled to 2 mK in a magneto optical trap operated on the1So-1P1transition at 461 nm. The second cooling stage utilizes the spin forbidden1So-3P1transition at 689 nm. To reach ultra-cold temperatures, 50 ms of broadband cooling is followed by 28 ms long single frequency cooling. The transfer efficiency from the first to the second cooling stage was measured to be 23%, leaving 7 x 106 atoms at a temperature of 1 muK. The atomic cloud is overlapped with a horizontally oriented 1-D far-off resonance optical dipole trap (FORT) at 813 nm with an effective potential depth of 25 muK. Due to equal light shifts of the1Soand the3P1state simultaneous Doppler cooling during the atom loading into the FORT is possible which leads to a transfer efficiency into the dipole trap of up to 60%.
We report on recent realization of an optical lattice clock operating on the1S0-3P0transition in88Sr, at LENS laboratories. The clock transition is excited with the technique of magnetic field-induced spectroscopy. New experimental techniques has also been developed in order to simplifies the clock spectroscopy in Sr atoms. The first new method helps in the first search of the clock transition without the use of extensive frequency metrology hardware and in particular optical frequency combs. This technique exploits a near coincidence in the atomic wavelengths of the1S0-3P0clock and1S0-3P1second stage cooling transitions in Sr, which are only 5 THz far apart. This coincidence enables the use of an optical (transfer) cavity to reference the frequency of the clock transition relative to that of the much stronger cooling transition. Secondly we reduce the complexity of the experimental setup by using only semiconductor laser sources in the apparatus. With this setup, about 10488Sr atoms are trapped in a 1D lattice formed by 200 mW of radiation tuned near the magic wavelength at 813 nm. We will present a first uncertainty budget for our optical lattice clock based on88Sr with particular attention to density dependent collisions, which led to an unexpectedly high signal contrast for long interaction times. In view of an absolute frequency measurement of clock transition we'll also present recent experimental results on optimization of an home made Ti:Sa optical frequency comb. Additionally, we anticipate that the simplification of the experimental setup presented will help address a wider range of applications including those requiring transportable devices. Along these lines we will report progress on the realization of the first transportable Sr optical lattice clock.