Abstracts Book - IMRC 2018

• SD7-O021
EXPLORING THE HYPERFINE STRUCTURE OF 133 Cs USING HIGH
RESOLUTION SPECTROSCOPIES IN THE OPTICAL AND
MICROWAVE REGION
Carlos Andrés Ortiz Cardona 1,2 , Eduardo de Carlos López 2 , J. Mauricio López Romero 1 , Sergio
Joaquín Jiménez Sandoval 1
1 Centro de Investigación y de Estudios Avanzados del IPN - CINVESTAV, Unidad Querétaro,
Mexico. 2 Centro Nacional de Metrologia, Dirección de Tiempo y Frecuencia, Mexico.
High-resolution measurements of hyperfine structure in the excited states of
alkali atoms provides a strongest testing ground for state-of-the-art atomic
calculations based on the best wavefunctions [1]. In particular measurements
of 133 Cs hyperfine structure are often limited by the linewidth of the transition.
In this work, we present the implementation of an Ultra-Stable Laser (USL) in
order to achieve a linewidth less than 100 Hz using an Extended Cavity Diode
Laser (ECDL) coupled to an Ultra-Low Expansion (ULE) optical cavity. The master
laser is a commercial AlGaAs equipped with a low loss interference filter, 852
nm wavelength and 20 kHz linewidth. The ULE Fabry-Pérot cavity has a free
spectral range of 1.49 GHz and a linewidth less than 2.3 kHz. In order to stabilize
the ECDL to the optical cavity and reduce its linewidth, the Pound-Drever Hall
technique is used [2]. Then, the USL is used to characterize the hyperfine
structure of 133 Cs using Modulation Transfer (MT) spectroscopy [3] which
generates dispersive-like lineshapes which sit on a flat, zero background.
Consequently, the zero-crossings of the modulation transfer signals are
accurately centered on the corresponding atomic transitions. The D 2 line
of 133 Cs is routinely used around the world to manipulate and cool Cs atoms in
order to materialize the SI time unit, the second. In Mexico, this experiment is
performed by the Centro Nacional de Metrología (CENAM) where Cs atoms are
manipulated using an USL. In order to maximize the interaction between light
and atoms, the laser frequency should be stabilized precisely. Therefore, an
accurate characterization of the 133 Cs atoms is particularly important in this kind
of experiments. In order to present the functionality of the atomic fountain as a
time and frequency standard, the Ramsey spectrum obtained with ultra highresolution
microwave spectroscopy of 133 Cs using the CENAM´s Cs fountain
clock (CsF 1 ) is reported. Ramsey fringes with an FWHM of 1.4 Hz were generated
from the induced decay between two hyperfine levels of 133 Cs ground state.