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Characterization of cold atomic cloud in a magneto-optical trap

Poonam Arora, Swatilekha Chowdhury, Ashish Agarwal, Kavindra Pant, Amitava Sen Gupta

Published Sep 1, 2011• 0 citations
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Abstract

The results of characterization of cold cloud of cesium (Cs) atoms trapped in a magneto-optical trap (MOT) have been presented. The MOT is a part of the Physics package of the Cs Fountain Clock being developed at National Physical Laboratory (NPL), India. The number of atoms, size and temperature of the cloud have been measured and calculated. It is also been investigated how the number of trapped atoms changes with the trapping laser’s beam intensity, detuning and magnetic-field gradient of the trap.

Related papers

Accurate absolute measurement of trapped Cs atoms in a MOT

M.A. Talavera

A Cs-133 Magneto-Optical Trap (MOT) has been developed at the Time and Frequency Division of the Centro Nacional de Metrolog´ CENAM, in Mexico. This MOT is part of a primary frequency standard based on ultra-cold Cs atoms, called CsF-1 clock, under development at CENAM. In this Cs MOT, we use the standard configuration (ae + i ae i ) 4-horizontal 2-vertical laser beams 1.9 cm in diameter, with 5 mW each. We use a 852 nm, 5 mW, DBR laser as a master laser which is stabilized by saturation spectroscopy. Emission linewidth of the master laser is 1 MHz. In order to amplify the light of the master laser, a 50 mW, 852 nm AlGaAs laser is used as slave laser. This slave laser is stabilized by light injection technique. A 12 MHz red shift of the light is performed by two double passes through two Acusto-Optic Modulators (AOMs). The optical part of the CENAMs MOT is very robust against mechanical vibration, acoustic noise and temperature changes in our laboratory, because none of our diode lasers use an extended cavity to reduce the linewidth. In this paper, we report results of our MOT characterization as a function of several operation parameters such as the intensity of laser beams, the laser beam diameter, the red shift of light, and the gradient of the magnetic field. We also report accurate absolute measurement of the number of Cs atoms trapped in our Cs MOT. We found up to6 £ 10 7 Cs atoms trapped in our MOT measured with an uncertainty no greater than 6.4%.

•Jan 1, 2007•1 citation

Laser cooling and trapping of Cs-133 neutral atoms at CENAM

M. Talavera-Ortega, J. M. López Romero, E. de Carlos López

At the moment the National Center of Metrology (CENAM) develops to the necessary technology for the creation of a frequency standard of high accuracy denominated CsF1 atomic fountain. The first stage of development of this clock consists of laser cooling and trapping neutral Cs-133 atoms. The mechanism of laser cooling and trapping of atoms requires of the accomplishment of a magneto-optical trap (MOT) in where is indispensable to maintain a strict control in its parameters of operation. In this experiment, the MOT operates with three set of red detuning |62s1/2, F=4|-> |62s3/2, F'=5| cyclical transition of Cs-133, mutually orthogonal, counterpropagating laser beams, with opposite circular polarization, intersecting at the center of a magnetic field which is generated by a pair of coil in anti-Helmholtz configuration. Additionally, a beam of light that comes from a repumping laser, tuned to the frequency of the |62s1/2, F=3|->|62s3/2, F'=4| transition of Cs-133, is injected to the MOT to maintain an atoms population in the |62s1/2, F=4| state. To cool and trap atoms to so low temperatures, of the order of the microkelvins on the zero absolute, by several seconds, minutes or even by several hours, provided the fundamentals tools to us to study the temporal and spatial behavior of the fluorescence of the atomic cloud and to make exact measurements in the count of such, in order to deduce the parameters of operation of the MOT that allows us to trap 1010 atoms or more. In this work the theoretical concepts as well as the experimental details of the parameters of operation of the MOT for the formation of the cold atom cloud are approached.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Feb 13, 2006•0 citations

Development of a MOT-based continuous cold Cs-beam atomic clock

H. Wang, Walter F. Buell

Summary form only given. We discuss our compact clock physics package and report the realization of a continuous, cold Cs atomic beam from a vapor-cell magneto-optical trap (MOT) of Cs atoms. Briefly, we generate the cold Cs beam by perturbing the trap potentials with a small opaque disk inserted in one of the MOT beams. Along the narrow dark column thus formed, Cs atoms are continuously accelerated out of the trap volume to form a Cs beam while the MOT remains in functioning of capturing and cooling Cs atoms from the Cs vapor. The fluorescence image of the Cs trap and the continuous Cs atomic beam are shown. Our MOT captures and confines 8 /spl times/ 10/sup 7/ Cs atoms at a loading rate of 2 /spl times/ 10/sup 8/ atoms/s and cools the atoms to a thermal temperature of 300 /spl mu/K. The longitudinal velocity of the cold Cs beam is measured by a time of flight (TOF) method. A single-shot laser-induced fluorescence signal recorded at a distance of 18 cm downstream from the MOT is shown. Under the nominal experimental conditions, the TOF measurement determines that our cold Cs atomic beam travels at 7 m/s and has a velocity spread of 0.9 m/s. With the cold Cs beam thus formed and a compact Ramsey cavity of 20 cm in length, we have estimated a short-term Allan deviation of 1.8 /spl times/ 10/sup -13/ /spl tau//sup -1/2/ (T is the averaging time) for the atomic clock under development.

Quantum Electronics and Laser Science Conference•Jun 25, 2003•1 citation

Update on the development of cesium atomic fountain at NPL, India

Poonam Arora, Ashish Agarwal, Kavindra Pant +2 more

National Physical Laboratory India (NPLI) has been developing a cesium atomic fountain primary frequency standard. We have succeeded in trapping about 107Cs atoms, cool them to about 5 μK by both magneto-optical trap (MOT) and polarization gradient cooling (PGC) and launch them up by moving molasses method. We have demonstrated the fountain action by launching the atoms up to 72.9 cm up and detection of the return signal by measuring the fluorescence. Work is underway to interrogate the launched atoms with microwaves and observe Ramsey fringes.

URSI General Assembly and Scientific Symposium•Aug 1, 2011•0 citations

Characterization of Magneto-optical Trap For Experiments in Light-Atom Interfacing

Pantita Palittapongarnpim

This thesis presents the study of atomic cloud density and temperature in a magneto-optical trap (MOT). The purpose is to find the method in obtaining the densest and coldest cloud the setup can produce. In steady state trap, the highest atomic density possible is that of a cloud in multiple scattering regime where a repulsive force between atoms sets a limit to the density. The number of atoms loaded into the trap is controlled by the trapping beam intensity which also changes the temperature. Therefore the trap density and temperature cannot be controlled separately. The cloud compression is studied as a method of increasing atomic density above what is possible in steady state trap without noticeable influence on the cloud temperature. Cloud compression is also found when the cloud is translated by changing the magnetic field zero-point although in a less predictable fashion than the compression.

•Jan 1, 2012•0 citations

Laser-cooled continuous Cs-beam master oscillator

H. Wang, Walter F. Buell, Gebriel H. Iyanu

In this paper, we present our design and prospects of a magneto-optical trap (MOT)-based cold Cs-beam atomic clock physics package and report the realization and characterization of a continuous, laser-cooled Cs atomic beam from a Cs MOT. We have determined the longitudinal velocity of the cold Cs beam by time of flight (TOF) method to be 7 m/s with a velocity spread of 1 m/s. By adjusting the MOT parameters, we are able to tune the Cs-beam velocity from 5 m/s to 8.5 m/s while the velocity spread remains to be 1 m/s. The Cs beam has an instantaneous atomic flux of 3.6 times 1010atoms/s when operated in pulsed mode and a continuous beam flux of 2 times 108atoms/s. Our theoretical simulation reveals that the MOT inhomogeneous magnetic field and the varying Doppler shift along the atomic beam propagation play an important role in determining the longitudinal velocity of the Cs atomic beam. With the cold Cs beam thus formed and a compact Ramsey cavity of 13 cm in length, we have estimated a short-term, shot-noise limited Allan standard deviation of 2.7 times 10-13pi-frac12(pi is the averaging time) for the atomic master oscillator under development

Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)•Jan 18, 2006•2 citations
The results of characterization of cold cloud of cesium (Cs) atoms trapped in a magneto-optical trap (MOT) have been
presented. The MOT is a part of the Physics package of the Cs Fountain Clock being developed at National Physical
Laboratory (NPL), India. The number of atoms, size and temperature of the cloud have been measured and calculated. It is also been investigated how the number of trapped atoms changes with the trapping laser’s beam intensity, detuning and magnetic-field gradient of the trap.
A Cs-133 Magneto-Optical Trap (MOT) has been developed at the Time and Frequency Division of the Centro Nacional de Metrolog´ CENAM, in Mexico. This MOT is part of a primary frequency standard based on ultra-cold Cs atoms, called CsF-1 clock, under development at CENAM. In this Cs MOT, we use the standard configuration (ae + i ae i ) 4-horizontal 2-vertical laser beams 1.9 cm in diameter, with 5 mW each. We use a 852 nm, 5 mW, DBR laser as a master laser which is stabilized by saturation spectroscopy. Emission linewidth of the master laser is 1 MHz. In order to amplify the light of the master laser, a 50 mW, 852 nm AlGaAs laser is used as slave laser. This slave laser is stabilized by light injection technique. A 12 MHz red shift of the light is performed by two double passes through two Acusto-Optic Modulators (AOMs). The optical part of the CENAMs MOT is very robust against mechanical vibration, acoustic noise and temperature changes in our laboratory, because none of our diode lasers use an extended cavity to reduce the linewidth. In this paper, we report results of our MOT characterization as a function of several operation parameters such as the intensity of laser beams, the laser beam diameter, the red shift of light, and the gradient of the magnetic field. We also report accurate absolute measurement of the number of Cs atoms trapped in our Cs MOT. We found up to6 £ 10 7 Cs atoms trapped in our MOT measured with an uncertainty no greater than 6.4%.
At the moment the National Center of Metrology (CENAM) develops to the necessary technology for the creation of a frequency standard of high accuracy denominated CsF1 atomic fountain. The first stage of development of this clock consists of laser cooling and trapping neutral Cs-133 atoms. The mechanism of laser cooling and trapping of atoms requires of the accomplishment of a magneto-optical trap (MOT) in where is indispensable to maintain a strict control in its parameters of operation. In this experiment, the MOT operates with three set of red detuning |62s1/2, F=4|-> |62s3/2, F'=5| cyclical transition of Cs-133, mutually orthogonal, counterpropagating laser beams, with opposite circular polarization, intersecting at the center of a magnetic field which is generated by a pair of coil in anti-Helmholtz configuration. Additionally, a beam of light that comes from a repumping laser, tuned to the frequency of the |62s1/2, F=3|->|62s3/2, F'=4| transition of Cs-133, is injected to the MOT to maintain an atoms population in the |62s1/2, F=4| state. To cool and trap atoms to so low temperatures, of the order of the microkelvins on the zero absolute, by several seconds, minutes or even by several hours, provided the fundamentals tools to us to study the temporal and spatial behavior of the fluorescence of the atomic cloud and to make exact measurements in the count of such, in order to deduce the parameters of operation of the MOT that allows us to trap 1010 atoms or more. In this work the theoretical concepts as well as the experimental details of the parameters of operation of the MOT for the formation of the cold atom cloud are approached.
Summary form only given. We discuss our compact clock physics package and report the realization of a continuous, cold Cs atomic beam from a vapor-cell magneto-optical trap (MOT) of Cs atoms. Briefly, we generate the cold Cs beam by perturbing the trap potentials with a small opaque disk inserted in one of the MOT beams. Along the narrow dark column thus formed, Cs atoms are continuously accelerated out of the trap volume to form a Cs beam while the MOT remains in functioning of capturing and cooling Cs atoms from the Cs vapor. The fluorescence image of the Cs trap and the continuous Cs atomic beam are shown. Our MOT captures and confines 8 /spl times/ 10/sup 7/ Cs atoms at a loading rate of 2 /spl times/ 10/sup 8/ atoms/s and cools the atoms to a thermal temperature of 300 /spl mu/K. The longitudinal velocity of the cold Cs beam is measured by a time of flight (TOF) method. A single-shot laser-induced fluorescence signal recorded at a distance of 18 cm downstream from the MOT is shown. Under the nominal experimental conditions, the TOF measurement determines that our cold Cs atomic beam travels at 7 m/s and has a velocity spread of 0.9 m/s. With the cold Cs beam thus formed and a compact Ramsey cavity of 20 cm in length, we have estimated a short-term Allan deviation of 1.8 /spl times/ 10/sup -13/ /spl tau//sup -1/2/ (T is the averaging time) for the atomic clock under development.
National Physical Laboratory India (NPLI) has been developing a cesium atomic fountain primary frequency standard. We have succeeded in trapping about 107Cs atoms, cool them to about 5 μK by both magneto-optical trap (MOT) and polarization gradient cooling (PGC) and launch them up by moving molasses method. We have demonstrated the fountain action by launching the atoms up to 72.9 cm up and detection of the return signal by measuring the fluorescence. Work is underway to interrogate the launched atoms with microwaves and observe Ramsey fringes.
This thesis presents the study of atomic cloud density and temperature in a magneto-optical trap (MOT). The purpose is to find the method in obtaining the densest and coldest cloud the setup can produce. In steady state trap, the highest atomic density possible is that of a cloud in multiple scattering regime where a repulsive force between atoms sets a limit to the density. The number of atoms loaded into the trap is controlled by the trapping beam intensity which also changes the temperature. Therefore the trap density and temperature cannot be controlled separately. The cloud compression is studied as a method of increasing atomic density above what is possible in steady state trap without noticeable influence on the cloud temperature. Cloud compression is also found when the cloud is translated by changing the magnetic field zero-point although in a less predictable fashion than the compression.
In this paper, we present our design and prospects of a magneto-optical trap (MOT)-based cold Cs-beam atomic clock physics package and report the realization and characterization of a continuous, laser-cooled Cs atomic beam from a Cs MOT. We have determined the longitudinal velocity of the cold Cs beam by time of flight (TOF) method to be 7 m/s with a velocity spread of 1 m/s. By adjusting the MOT parameters, we are able to tune the Cs-beam velocity from 5 m/s to 8.5 m/s while the velocity spread remains to be 1 m/s. The Cs beam has an instantaneous atomic flux of 3.6 times 1010atoms/s when operated in pulsed mode and a continuous beam flux of 2 times 108atoms/s. Our theoretical simulation reveals that the MOT inhomogeneous magnetic field and the varying Doppler shift along the atomic beam propagation play an important role in determining the longitudinal velocity of the Cs atomic beam. With the cold Cs beam thus formed and a compact Ramsey cavity of 13 cm in length, we have estimated a short-term, shot-noise limited Allan standard deviation of 2.7 times 10-13pi-frac12(pi is the averaging time) for the atomic master oscillator under development