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Indium Single-Ion Frequency Standard

Warren Nagourney

Published Jan 1, 2001• 0 citations

Abstract

A single laser-cooled indium ion is a promising candidate for an ultimate resolution optical time or frequency standard. It can be shown that single ions from group IIIA of the periodic table (indium, thallium, etc.) can have extremely small systematic errors. In addition to being free from Doppler, transit-time and collisional shifts, these ions are also quite insensitive to perturbations from ambient magnetic and electric fields (mainly due to the use of a J=0-0 transition for spectroscopy). Of all group IIIA ions, indium seems to be the most practical, since it is heavy enough to have a tolerable intercombination cooling transition rate and (unlike thallium) has transitions which are easily accessible with frequency multiplied continuous-wave lasers. A single indium ion standard has a potential inaccuracy of one part in 10(exp 18) for integration times of 10(exp 6) seconds. We have made substantial progress during the grant period in constructing a frequency standard based upon a single indium ion. At the beginning of the grant period, single indium ions were being successfully trapped, but the lasers and optical systems were inadequate to achieve the desired goal. We have considerably improved the stability of the dye laser used to cool the ions and locked it to a molecular resonance line, making it possible to observe stable cooling-line fluorescence from a single indium ion for reasonable periods of time, as required by the demands of precision spectroscopy. We have substantially improved the single-ion fluorescence signal with significant benefits for the detection efficiency of forbidden transitions using the 'shelving' technique. Finally, we have constructed a compact, efficient UV 'clock' laser and observed 'clock' transitions in single indium ions using this laser system. We will elaborate on these accomplishments.

Related papers

Indium single ion optical frequency standard

T. Becker, M. Eichenseer, Alexander Yu. Nevsky +5 more

A single laser cooled ion in a radiofrequency trap can serve as the basis for a highly stable optical frequency standard. We present recent results of our work on single indium ions, using the /sup 1/S/sub 0/ to /sup 3/P/sub 0/ transition at 236.5 nm wave-length as the clock transition. This resonance has a linewidth of only 0.82 Hz where systematic shifts should be controllable on the mHz level. A single In/sup +/ ion is stored in a miniature Paul-Straubel trap and laser cooled to a temperature of about 100 /spl mu/K. The clock transition is excited using a frequency quadrupled Nd:YAG laser. A fractional resolution of 1.3/spl middot/10/sup -13/ has been achieved so far (linewidth of 170 Hz at 1267 THz). The absolute frequency of the clock transition clock transition has been measured with an uncertainty of 2/spl middot/10/sup -13/ using a frequency chain and a methane-stabilized HeNe laser as a reference, that was calibrated with a cesium clock.

Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)•Nov 13, 2002•3 citations

Indium single-ion optical frequency standard

Thomas P. Becker, M. Eichenseer, Alexander Yu. Nevsky +5 more

Single laser-cooled ions in radiofrequency traps can serve as the basis for highly stable optical frequency standards. Here we present recent results on In+, using the 1S0 yields 3P0 line at 236.5 nm wavelength as the clock transition. This resonance has a natural linewidth of only 0.82 Hz and systematic shifts should be controllable at the mHz level. A single indium ion is stored in a miniature Paul- Straubel trap and laser cooled to a temperature of about 100 (mu) K. The clock transition is excited using a frequency quadrupled 946 nm Nd:YAG laser. A fractional resolution of 1.3 (DOT) 10-13 has been achieved so far (linewidth of 170 Hz at 1267 THz). The absolute optical frequency of the clock transition has been measured with an uncertainty being less than 3 (DOT) 10-13 using a frequency chain and a methane-stabilized HeNe laser that was calibrated with a cesium clock.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•May 3, 2001•0 citations

Optical frequency standard based upon single laser-cooled indium ion

Warren Nagourney, Justin R. Torgerson, HANS G. DEHMELT

The current state of our single indium ion work will be presented, with emphasis on the construction of a narrow, solid-state source of tunable UV radiation which will serve as a “clock” laser for the single-ion standard. Indium is shown to be a favorable candidate for a standard with a long term inaccuracy of less than one part in 1017. Its advantages are small systematic errors which are well-understood and relatively straightforward generation of the cooling and “clock” radiation. The stringent requirements on the long term stability of the “flywheel” clock laser and the difficulty in coherently relating the optical clock laser frequency to a convenient microwave source are problems which should soon be overcome.

AIP conference proceedings•Jan 1, 1999•2 citations

Spectroscopy of Single Trapped Ions and Application to Frequency Standards

HERBERT WALTHER

Single ions trapped and laser cooled provide ideal objects for high resolution spectroscopy and frequency standards. For the latter purpose we are investigating the 5s2 1S0 → 5s5p 3P0 transition of In+. With a natural linewidth of only 1.1 Hz this resonance offers very high resolution and is highly immune to frequency shifts due to external electromagnetic fields, because it connects two levels with vanishing electronic magnetic momenta [1]. The wavelength of this clock transition is 236.5 nm and is technically very convenient, since it coincides with the fourth harmonic of the 946 nm Nd:YAG laser line. So this intrinsically frequency stable solid-state laser can be used to excite the transition [2]. For laser cooling and fluorescence detection of the indium ion the 5s2 1So -> 5s5p 3P1 transition at 230.6 nm can be employed. The use of the relatively narrow intercombination line for laser cooling allows us to study optical sideband cooling in the strong binding regime, where the oscillation frequencies of the ion in the trap (around 1 MHz) are larger than the optical linewidth of 360 kHz. In this parameter range laser cooling is possible to the quantum ground state of the vibrational motion in the trap corresponding to a temperature of roughly 100 μK. The same low temperature was obtained with sideband cooling of a small Coulomb crystal consisting of two ions, creating an interesting new quantum few-particle system.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jan 1, 1998•0 citations

Narrow-linewidth laser system for precise spectroscopy of the indium ion clock transition

Alexander Yu. Nevsky, M. Eichenseer, E. Peik +2 more

Summary form only given. A single laser-cooled indium ion, stored in a radio-frequency trap, is expected to be one of the most promising candidates for the creation of a new generation of optical frequency standards with an anticipated accuracy of up to 10/sup -18/. On the way to achieving such a high level of accuracy, one of the main limitations is the short-term frequency instability of the laser system, used to excite the narrow /sup 1/S/sub 0/-/sup 3/P/sub 0/ In/sup +/ clock transition. Since the signal from the single ion is small, the laser system should posses extremely high frequency stability (on the level of /spl Delta/v/v=10/sup -14//spl divide/10/sup -15/) for averaging times of about one second in order to reduce statistical uncertainties and to minimize the time of experiment. In this paper, we report our recent results on the improvement of the short-term frequency stability of the laser system.

Quantum Electronics and Laser Science Conference•Nov 13, 2002•0 citations

Spectroscopy with single-trapped ions

HERBERT WALTHER

In this paper experiments with single trapped ions are reviewed. They are performed with the aim of developing a new frequency standard and to perform cavity quantum electrodynamics experiments with single ions. For a new optical frequency standard we are investigating the 5s21S0 implied by 5s5p3P0 transition of a single trapped laser-cooled 115In(superscript + ion. This line with a natural linewidth of only 0.8 Hz is highly immune to systematic frequency shifts. For sideband laser cooling and fluorescence detection of the indium ion the 5s21S0 implied by 5s5p3P1 transition at 230.6 nm is used. Temperatures below 100 (mu) K and a mean vibrational quantum number <n><1 of the ion in the trap have been reached. For the clock transition a resolution of 1.3 multiplied by 10-13 (linewidth 170 Hz) has been obtained so far, limited by the short term frequency fluctuations of the clock laser. The absolute frequency of the 1S0 implied by 3P0 transition was measured by making a link to the reference frequency of the methane-stabilized HeNe laser using a frequency chain. In the second part of the paper the present status of the experiments on the ion trap laser are briefly described.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Jun 29, 2001•0 citations

A single laser-cooled indium ion is a promising candidate for an ultimate resolution optical time or frequency standard. It can be shown that single ions from group IIIA of the periodic table (indium, thallium, etc.) can have extremely small systematic errors. In addition to being free from Doppler, transit-time and collisional shifts, these ions are also quite insensitive to perturbations from ambient magnetic and electric fields (mainly due to the use of a J=0-0 transition for spectroscopy). Of all group IIIA ions, indium seems to be the most practical, since it is heavy enough to have a tolerable intercombination cooling transition rate and (unlike thallium) has transitions which are easily accessible with frequency multiplied continuous-wave lasers. A single indium ion standard has a potential inaccuracy of one part in 10(exp 18) for integration times of 10(exp 6) seconds. We have made substantial progress during the grant period in constructing a frequency standard based upon a single indium ion. At the beginning of the grant period, single indium ions were being successfully trapped, but the lasers and optical systems were inadequate to achieve the desired goal. We have considerably improved the stability of the dye laser used to cool the ions and locked it to a molecular resonance line, making it possible to observe stable cooling-line fluorescence from a single indium ion for reasonable periods of time, as required by the demands of precision spectroscopy. We have substantially improved the single-ion fluorescence signal with significant benefits for the detection efficiency of forbidden transitions using the 'shelving' technique. Finally, we have constructed a compact, efficient UV 'clock' laser and observed 'clock' transitions in single indium ions using this laser system. We will elaborate on these accomplishments.

A single laser cooled ion in a radiofrequency trap can serve as the basis for a highly stable optical frequency standard. We present recent results of our work on single indium ions, using the /sup 1/S/sub 0/ to /sup 3/P/sub 0/ transition at 236.5 nm wave-length as the clock transition. This resonance has a linewidth of only 0.82 Hz where systematic shifts should be controllable on the mHz level. A single In/sup +/ ion is stored in a miniature Paul-Straubel trap and laser cooled to a temperature of about 100 /spl mu/K. The clock transition is excited using a frequency quadrupled Nd:YAG laser. A fractional resolution of 1.3/spl middot/10/sup -13/ has been achieved so far (linewidth of 170 Hz at 1267 THz). The absolute frequency of the clock transition clock transition has been measured with an uncertainty of 2/spl middot/10/sup -13/ using a frequency chain and a methane-stabilized HeNe laser as a reference, that was calibrated with a cesium clock.

Single laser-cooled ions in radiofrequency traps can serve as the basis for highly stable optical frequency standards. Here we present recent results on In+, using the 1S0 yields 3P0 line at 236.5 nm wavelength as the clock transition. This resonance has a natural linewidth of only 0.82 Hz and systematic shifts should be controllable at the mHz level. A single indium ion is stored in a miniature Paul- Straubel trap and laser cooled to a temperature of about 100 (mu) K. The clock transition is excited using a frequency quadrupled 946 nm Nd:YAG laser. A fractional resolution of 1.3 (DOT) 10-13 has been achieved so far (linewidth of 170 Hz at 1267 THz). The absolute optical frequency of the clock transition has been measured with an uncertainty being less than 3 (DOT) 10-13 using a frequency chain and a methane-stabilized HeNe laser that was calibrated with a cesium clock.

The current state of our single indium ion work will be presented, with emphasis on the construction of a narrow, solid-state source of tunable UV radiation which will serve as a “clock” laser for the single-ion standard. Indium is shown to be a favorable candidate for a standard with a long term inaccuracy of less than one part in 1017. Its advantages are small systematic errors which are well-understood and relatively straightforward generation of the cooling and “clock” radiation. The stringent requirements on the long term stability of the “flywheel” clock laser and the difficulty in coherently relating the optical clock laser frequency to a convenient microwave source are problems which should soon be overcome.

Single ions trapped and laser cooled provide ideal objects for high resolution spectroscopy and frequency standards. For the latter purpose we are investigating the 5s2 1S0 → 5s5p 3P0 transition of In+. With a natural linewidth of only 1.1 Hz this resonance offers very high resolution and is highly immune to frequency shifts due to external electromagnetic fields, because it connects two levels with vanishing electronic magnetic momenta [1]. The wavelength of this clock transition is 236.5 nm and is technically very convenient, since it coincides with the fourth harmonic of the 946 nm Nd:YAG laser line. So this intrinsically frequency stable solid-state laser can be used to excite the transition [2]. For laser cooling and fluorescence detection of the indium ion the 5s2 1So -> 5s5p 3P1 transition at 230.6 nm can be employed. The use of the relatively narrow intercombination line for laser cooling allows us to study optical sideband cooling in the strong binding regime, where the oscillation frequencies of the ion in the trap (around 1 MHz) are larger than the optical linewidth of 360 kHz. In this parameter range laser cooling is possible to the quantum ground state of the vibrational motion in the trap corresponding to a temperature of roughly 100 μK. The same low temperature was obtained with sideband cooling of a small Coulomb crystal consisting of two ions, creating an interesting new quantum few-particle system.

Summary form only given. A single laser-cooled indium ion, stored in a radio-frequency trap, is expected to be one of the most promising candidates for the creation of a new generation of optical frequency standards with an anticipated accuracy of up to 10/sup -18/. On the way to achieving such a high level of accuracy, one of the main limitations is the short-term frequency instability of the laser system, used to excite the narrow /sup 1/S/sub 0/-/sup 3/P/sub 0/ In/sup +/ clock transition. Since the signal from the single ion is small, the laser system should posses extremely high frequency stability (on the level of /spl Delta/v/v=10/sup -14//spl divide/10/sup -15/) for averaging times of about one second in order to reduce statistical uncertainties and to minimize the time of experiment. In this paper, we report our recent results on the improvement of the short-term frequency stability of the laser system.

In this paper experiments with single trapped ions are reviewed. They are performed with the aim of developing a new frequency standard and to perform cavity quantum electrodynamics experiments with single ions. For a new optical frequency standard we are investigating the 5s21S0 implied by 5s5p3P0 transition of a single trapped laser-cooled 115In(superscript + ion. This line with a natural linewidth of only 0.8 Hz is highly immune to systematic frequency shifts. For sideband laser cooling and fluorescence detection of the indium ion the 5s21S0 implied by 5s5p3P1 transition at 230.6 nm is used. Temperatures below 100 (mu) K and a mean vibrational quantum number <n><1 of the ion in the trap have been reached. For the clock transition a resolution of 1.3 multiplied by 10-13 (linewidth 170 Hz) has been obtained so far, limited by the short term frequency fluctuations of the clock laser. The absolute frequency of the 1S0 implied by 3P0 transition was measured by making a link to the reference frequency of the methane-stabilized HeNe laser using a frequency chain. In the second part of the paper the present status of the experiments on the ion trap laser are briefly described.