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  Laser Cooling - Abstracts

Phys. Rev. A 64, 023412 (2001)

Theory and Experiment of a Magneto Optical Trap Operating on a Novel Mechanism Based on Level Mixing.
K.Nasyrov1,3, V.Biancalana1, A.Burchianti1,
R.Calabrese2, C.Marinelli1, E.Mariotti1, and L.Moi1.

1. Dipartimento di Fisica dell'Università and INFM UdR di Siena, I-53100 Siena, Italy
2. Dipartimento di Fisica dell'Università and INFN, I-44100 Ferrara, Italy
3. Permanent address: Institute of Automation and Electrometry, Novosibirsk 90, Russia

In this work we point out a new theoretical picture accounting for some unpredicted trapping conditions that have been observed - but not satisfactorily explained- in the past and have been recently confirmed by our experiments. We have realized a sodium MOT working on the 3 2S1/2, F=1 --> 32P3/2, F=0 transition that, according to the usually accepted model, should not work. Our results, with respect to the previous unexplained observations, support more stringent conclusions because our experimental set-up gives us the possibility to repump atoms from the F=2 state using D1 transitions. This definitely excludes that the repumping frequency may play a role in the trap dynamics. A peculiar perturbation approach allows us to demonstrate that the confinement force originates, in this case, from a magnetically induced level-mixing effect.

Moreover, we describe separately the nature of damping and confining forces and we recognize that in this case they are due to different transitions. Trap simulations based on a dynamical three-dimensional model are presented, which quantitatively reproduce our experimental results.

PACS:
32.80.Pj: Optical cooling of atoms; trapping.
42.50.Vk: Mechanical effects of light on atoms, molecules, electrons, and ions
32.60.+i: Zeeman and Stark effects

Published in Hyperfine Interactions 127, pages 503-506 (2000)

Development of a broadband laser in the UV region

S.N. Atutov1, V. Biancalana2, R. Calabrese1, V. Guidi1, P. Lenisa1, B. Mai1, E. Mariotti2, L. Moi2, L. Tomassetti1.

1 Dipartimento di Fisica dell'Università and INFN, I-44100 Ferrara, Italy
2 Dipartimento di Fisica dell'Università and INFM, I-53100 Siena, Italy

A frequency comb in the UV region with a bandwidth greater than 100 MHz is generated by successive frequency shifts of a single mode laser by an acousto-optic modulator coupled to a passive ring cavity. The obtained spectrum is particularly suitable for laser cooling when a large velocity capture range is required as in the case, for example, of ions confined in a storage ring. Keywords: broadband laser, ultraviolet, ion cooling

JOSA B 18, (2001) 335-339

Achromatic optical device for generation of a broadband frequency spectrum with high frequency stability and sharp termination

S.N. Atutov1,2, W.Baldini1, V.Biancalana3, R.Calabrese1, V.Guidi1, P.Lenisa1, B. Mai1,  E.Mariotti3, L.Moi3, L.Tomassetti1.

1 Dipartimento di Fisica dell'Università and INFN, I-44100 Ferrara, Italy
2 Permanent address: Institute of Automation and Electrometry, Novosibirsk 90, Russia
3 Dipartimento di Fisica dell'Università and INFM, I-53100 Siena, Italy

We have implemented a new optical scheme to produce a broadband frequency spectrum with customizable shape and high stability. The scheme consists of generation of mode structure by allowing a frequency-stabilized single-mode laser to pass through an acousto-optical modulator working under Raman-Nath regime. It comes out in several diffracted beams shifted by the frequency of acoustic waves in the acousto-optical modulator, DW. Diffracted beams are merged into only one beam by means of a telescope. The scheme works in either visible or UV range: frequency spectra as wide as nDeltaFM with n=7 have been achieved, resulting in 225 MHz and 150 MHz for the visible and UV spectral regions, respectively. The spectra possess the same stability as the primary single-mode laser. Their profile may exhibit a sharp termination on one side of the spectrum so that they can be utilized for high-efficiency laser cooling of an ion beam in a storage ring.

Eur.Phys.J.D. 13 (2001) 71

Sodium MOT collection efficiency as a function of the trapping and repumping laser frequencies and intensities

S.N.Atutov#^, V.Biancalana$, A.Burchianti$, R.Calabrese#, S.Gozzini*, V. Guidi#, P.Lenisa#, C.Marinelli$, E.Mariotti$, L.Moi$, K. Nasyrov$^, S. Pod'yachev$^

# Dipartimento di Fisica Università di Ferrara and INFN - sezione di Ferrara
$ INFM and Dipartimento di Fisica Università di Siena
* Istituto di Fisica Atomica e Molecolare del CNR - Pisa
^Permanent address: Institute for Automation and Electrometry, Novosibirsk

A detailed theoretical and experimental description of a sodium MOT as a function of the pumping and repumping laser frequencies and intensities is given. The effective trapping schemes and the collection efficiency have been experimentally measured and calculated by solving an original 3-D model. This model considers the whole bunch of the 32 ground and excited (P1/2 + P3/2) Zeeman sublevels, the actual trap geometry, the magnetic field intensity and direction, the light polarization, and evaluates both the velocity capture range vc and the number of trapped particles N.
Synergetic and competition mechanisms due to the trapping and repumping lasers have been predicted and experimentally observed. The model simulation has been compared with the results reported in the literature and with those obtained by us and a quite good agreement has been found. The model can be easily adapted to the other sodium isotopes as well as to all the other alkalis.

PACS:
32.80.Pj: Optical cooling of atoms; trapping
42.50.Vk: Mechanical effects of light on atoms, molecules, electrons, and ions
32.60.+i: Zeeman and Stark effects

Published in PRL 80, 10, page 2129 (1998)

White-light laser cooling of a fast stored ion beam.

S.N.Atutov, R.Calabrese, R.Grimm, V.Guidi, I,Lauer, P.Lenisa, V.Luger, E.Mariotti, L.Moi, A.Peters, U.Schramm, M.Stoessel

We report the experimental demonstration of white light laser cooling of high-velocity 7Li+ ion beam stored at 6.4% c in a storage ring. In a direct comparison with single mode laser cooling, we show that white light cooling is much more efficint to counteract strong intrabeam heating and leads to lower longitudinal beam temperatures at higher ion densities, i.e., much higher densities in the longitudinal phase space.

PACS: 29.20.Dh, 32.80.Pj, 42.50.Vk

Published in Optics Communications 146 (1998)196

Frequency stabilization of a broad-band dye laser by light-induced drift

S.N Atutov°# , R. Calabrese°,V. Guidi°, P. Lenisa°, E. Mariotti*, L.Moi*,
S. Petruio° and A.M. Shalagin *#

° INFN - Sez. di Ferrara e Dipartimento di Fisica dell'Universita',I-44100, Ferrara, Italy.
* INFM - Dipartimento di Fisica dell' Universita', I-53100, Siena, Italy.

A new method for the frequency locking of a broad-band laser based on light-induced drift is presented. The main advantages of the technique are: satisfactory stabilization provided by the sensitivity and the good signal-to-noise ratio of the error signal, the obviation of the necessity to juggle the laser frequency, the use of an atomic transition with low frequency drift. The method is well-suited to broad-band applications because the light-induced drift effect can integrate naturally over a broad band of frequencies (on the order of Doppler width) to find the average.
Tests carried out on Na immersed in a buffer gas of Ar, have allowed long-term frequency stabilization of the central frequency of a 2.5GHz-bandwidth dye laser to a better than 300 KHz.

PACS: 42.60, 42.50

Published in Optics Communications 132 (1996) 269

Generation of a frequency comb with a sharp edge of adjustable intensity and frequency

S.N.Atutov1, F.Bonazzi1-2, R.Calabrese1-2, V.Guidi1-2, P.Lenisa1-2, S.Petruio1-2, E.Mariotti3, L.Moi3

1INFN - Sezione di Ferrara, I-44100 Ferrara, Italy
2Dipartimento di Fisica dell'Universita', I-44100 Ferrara, Italy
3INFM-Dipartimento di Fisica dell'Universita', I-53100 Siena, Italy

A frequency comb is generated by successive frequency shifts of a single mode laser by an acousto-optic modulator coupled to a passive ring cavity. The cavity design and the laser-cavity coupling have a very high efficiency and allow for a perfect control of both the frequency and the intensity of the sharp edge. A second acousto-optic modulator can be used to double the comb bandwidth.  The obtained spectrum is particularly suitable for laser cooling when a large velocity capture range is required as it is the case, for example, of ions confined in a storage ring.

PACS: 3280P, 4260F

Published in  Optics Communications 123 (1996) 530

Transverse laser cooling of ions in a storage ring.

R.Calabrese1, V.Guidi1, P. Lenisa1, E.Mariotti2, L.Moi2

1 Dipartimento di Fisica dell'Università, I-44100, Ferrara, Italy INFN - Sezione di Ferrara, Italy
2 INFM - Unità di Siena, I-53100, Siena, Italy -Dipartimento di Fisica dell'Università, Siena Italy

We propose a method for a direct transverse laser cooling of ions in a storage ring and we discuss its application to 7Li+ and 24Mg+ ions studied in present storage rings. The key idea consists in the use of a broad-band laser which, impinging transversely on the ion beam to be cooled, causes phase-space compression through resonance radiation pressure. Our technique, by allowing simultaneous resonant excitation of almost all ions regardless of their velocity, compensates for the short laser-ion interaction time and gives a very large capture range.

PACS :
32.80.Pj Optical cooling of atoms; trapping.
42.50.Vk Mechanical effects of light on atoms, molecules, electrons and ions.
29.20.Dh Storage rings.

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