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An Injection-locked Diode Laser for Cold Rydberg Atom Experiments

Margaret S. Martei, Anders Wood, Duncan Tate

Published Jan 1, 2007• 0 citations
OpenAlex

Abstract

A free-running, temperature stabilized diode laser has been injection-locked to an external cavity diode laser for use in cold Rydberg atom experiments. Cold rubidium atoms in a magneto-optical trap (MOT) are excited to Rydberg states using a 10 ns laser pulse. The Rydberg atoms spontaneously ionize due to dipole forces, and the collisional ionization dynamics are observed as a function of atom density and principal quantum number of the Rydberg state, n. The injection-locked diode laser will be used as a repumper in conjunction with a dark spontaneous-force optical trap (SPOT) to increase the Rydberg state density. We report on the design of the injection-locked laser system.

Related papers

Diode lasers for use in experiments on cold Rydberg Atoms

Bill Whitledge

This project was to measure the atomic density of (85)Rb atoms in a magneto optical trap using a low-intensity probe laser. Additionally, a dark spontaneous force optical trap was constructed in an attempt to boost the trap density. The dark spot failed to appreciably increase the overall trap density (which remained steady at - N = 10^10 atoms/cm^3) but it did increase the density of dark-state atoms in the trap by an order of magnitude. This is a useful result since many experiments on cold Rydberg atoms involve exciting atoms starting in the ground state rather than the first excited state, which is occupied by a large number of atoms in a traditional magneto optical trap. The dark spot trap shows promise for boosting both the density of dark state atoms in the trap as well as the overall trap density. However, the latter goal will require further adjustment to the trap.

•Jan 1, 2008•1 citation

Long-lived states in cold Rydberg gases

D. Feldbaum, S.K. Dutta, Alisa I. Walz‐Flannigan +2 more

Summary form only given. Laser-cooled atoms can be excited into Rydberg states to study Rydberg gases at high densities and low atomic velocities. Dense clouds of such atoms undergo virtually complete ionization when their density exceeds a critical value dependent on the principal quantum number n. We report a new regime in which the excited Rydberg population spontaneously evolves into long-lived high-l states, the lifetimes of which exceed the natural lifetimes of the initially excited Rydberg levels by two orders of magnitude. /sup 87/Rb atoms are collected and cooled to 50 /spl mu/K in a magneto optical trap (MOT), which is periodically turned off for 50 ms. 1 ms after the shutdown of the MOT the Rydberg atoms are created via a two-step excitation process using a 5 /spl mu/s long diode laser pulse.

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

Assembling and Characterizing the Efficiency of an Injection Locked Laser System for Cold Neutral Atom Optical Traps

Alexandra Papa Crawford

Creating a quantum computer requires a system of particles that can be well-controlled to achieve quantum operations. We need a large array of these particles – called qubits – with long coherence times, which can be initialized, operated on by single and two qubit gates, and read out. For neutral atoms, the qubit states are stable ground states that interact minimally with the environment, leading to long coherence times. Experimentally, the qubits are manipulated using carefully timed laser beam pulses with controlled frequency and intensity, but the outstanding issue for optically trapping cold atoms is finding a light pattern that can hold an array of individually addressable atoms to perform these quantum operations. To solve this, pinhole diffraction patterns were previously computationally analyzed to trap a 2D array of qubits within localized bright and dark spots. This project implements an injection locked laser into this system to provide a high power, tunable light source for the pinhole diffraction pattern atomic trap. In this project, the injection locked laser system is tuned to and analyzed at 780 nm to observe the locking efficiency as a function of the laser diode temperature or current supplied to the tuned-frequency laser diode, also known as the seed laser. Data taken on the injection lock efficiency over varying seed laser power in the system, current supplied to the seed laser diode, and laser diode temperature confirm that there is a large dependence upon each of these settings. An optimal combination of seed laser diode temperature and current supplied to it can be found to provide an efficient and stable power source for the atomic trap.

•Jan 1, 2018•0 citations

Efficient magneto-optical trapping of Yb atoms with a violet laser diode

Chang Yong Park, Tai Hyun Yoon

We report an efficient trapping of rare-earth-metal Yb atoms with a high-power violet laser diode (LD). An injection-locked violet LD with a 25-mW frequency-stabilized output was used for the magneto-optical trapping (MOT) of fermionic as well as bosonic Yb isotopes. A typical number of $4\ifmmode\times\else\texttimes\fi{}{10}^{6}$ atoms for ${}^{174}\mathrm{Yb}$ with a trap density of $\ensuremath{\sim}1\ifmmode\times\else\texttimes\fi{}{10}^{8}{\mathrm{cm}}^{\ensuremath{-}3}$ was obtained. A 10-mW violet external-cavity LD was used for the one-dimensional slowing of an effusive Yb atomic beam without a Zeeman slower resulting in a 35-fold increase in the number of trapped atoms. The overall characteristics of our compact violet MOT, e.g., the loss time of 1 s, the loading time of 400 ms, and the cloud temperature of 0.7 mK, are comparable to those in previously reported violet Yb MOTs, yet with a greatly reduced cost and complexity of the experiment.

arXiv:physics/0309034•Physical Review A•Nov 11, 2003•49 citations

Magneto-Optical Trap for Cesium Atoms Without a Separate Repumping Laser

Junxian Fu, Xuzong Chen, Yi-min Li +2 more

A magneto-optical trap (MOT) for cesium atoms that operates without a separate repumping laser is reported. The differences between a normal MOT and this kind of MOT have been experimentally studied. The influences of a repumping laser on cooling and trapping cesium atoms in the MOT have been carefully investigated. The results reveal that it is the critical injection-locked state of the diode laser that makes magneto-optical trapping of cesium atoms possible without a separate repumping laser.

Chinese Physics Letters•Nov 1, 1999•2 citations

Trapping cold atoms with ultrafast laser pulses

L.C. Karssen

The aim of this research is to pave the way for making a trap for cold neutral atoms based on the force generated by pulses of a mode-locked laser. As an onset towards such a trap we decided to use a far-off-resonance trap (FORT) loaded with cold rubidium atoms from a magneto-optical trap (MOT). Our FORT setup consists of a titanium-sapphire laser that can operate both in continuous wave mode and in mode-locked mode. Our MOT setup uses a magnetic field gradient, and two diode lasers whose frequency is locked very accurately to the atomic transition using polarisation spectroscopy. Since the measurements we do require very precise timing of the order of less than one millisecond between the various phases of the experiment, a time-sequencing program was developed. Using this sophisticated setup, several characteristics of FORTs made with continuous and pulsed lasers were analysed. For example, we have investigated the loading behaviour of the traps and found that under general circumstances there is no significant difference. However, under special conditions it is possible to load more atoms into a pulsed trap. The lifetime of the number of atoms in the trap shows no dependence on the power of the trap laser in the continuous case. For the pulsed trap, however, the increased scattering due to the high peak intensities of the pulses does limit the achievable lifetimes. Moreover, due to the presence of a large number of photoassociation lines, i.e. lines were loosely bound molecules are formed by the interaction of two atoms an a photon, the two-particle losses depend heavily on the wavelength of the trap laser. Furthermore we have done measurements of the temperature of the trapped atoms, which revealed that the temperature is a constant fraction of the trap depth. We also looked at the effects of parametric excitation of the atoms in the FORT. The anharmonicity of the trap formed by the titanium-sapphire laser results in interesting physics, including a change in the average temperature of the atoms, depending on the modulation frequency. We also investigated the trapping behaviour of the FORT at low pulse repetition rates by switching the laser intensity on and off on a kHz scale. We investigated the dependence of the number of atoms on the polarisation of the FORT laser light, both for continuous and pulsed traps. Atoms can be trapped at elliptical polarisations as well, although the number of trapped atoms is less. As the laser is detuned further to the red of the rubidium D line, this effect becomes less and less pronounced, as predicted by our model.

•Mar 1, 2003•1 citation
A free-running, temperature stabilized diode laser has been injection-locked to an external cavity diode laser for use in cold Rydberg atom experiments. Cold rubidium atoms in a magneto-optical trap (MOT) are excited to Rydberg states using a 10 ns laser pulse. The Rydberg atoms spontaneously ionize due to dipole forces, and the collisional ionization dynamics are observed as a function of atom density and principal quantum number of the Rydberg state, n. The injection-locked diode laser will be used as a repumper in conjunction with a dark spontaneous-force optical trap (SPOT) to increase the Rydberg state density. We report on the design of the injection-locked laser system.
This project was to measure the atomic density of (85)Rb atoms in a magneto optical trap using a low-intensity probe laser. Additionally, a dark spontaneous force optical trap was constructed in an attempt to boost the trap density. The dark spot failed to appreciably increase the overall trap density (which remained steady at - N = 10^10 atoms/cm^3) but it did increase the density of dark-state atoms in the trap by an order of magnitude. This is a useful result since many experiments on cold Rydberg atoms involve exciting atoms starting in the ground state rather than the first excited state, which is occupied by a large number of atoms in a traditional magneto optical trap. The dark spot trap shows promise for boosting both the density of dark state atoms in the trap as well as the overall trap density. However, the latter goal will require further adjustment to the trap.
Summary form only given. Laser-cooled atoms can be excited into Rydberg states to study Rydberg gases at high densities and low atomic velocities. Dense clouds of such atoms undergo virtually complete ionization when their density exceeds a critical value dependent on the principal quantum number n. We report a new regime in which the excited Rydberg population spontaneously evolves into long-lived high-l states, the lifetimes of which exceed the natural lifetimes of the initially excited Rydberg levels by two orders of magnitude. /sup 87/Rb atoms are collected and cooled to 50 /spl mu/K in a magneto optical trap (MOT), which is periodically turned off for 50 ms. 1 ms after the shutdown of the MOT the Rydberg atoms are created via a two-step excitation process using a 5 /spl mu/s long diode laser pulse.
Creating a quantum computer requires a system of particles that can be well-controlled to achieve quantum operations. We need a large array of these particles – called qubits – with long coherence times, which can be initialized, operated on by single and two qubit gates, and read out. For neutral atoms, the qubit states are stable ground states that interact minimally with the environment, leading to long coherence times. Experimentally, the qubits are manipulated using carefully timed laser beam pulses with controlled frequency and intensity, but the outstanding issue for optically trapping cold atoms is finding a light pattern that can hold an array of individually addressable atoms to perform these quantum operations. To solve this, pinhole diffraction patterns were previously computationally analyzed to trap a 2D array of qubits within localized bright and dark spots. This project implements an injection locked laser into this system to provide a high power, tunable light source for the pinhole diffraction pattern atomic trap. In this project, the injection locked laser system is tuned to and analyzed at 780 nm to observe the locking efficiency as a function of the laser diode temperature or current supplied to the tuned-frequency laser diode, also known as the seed laser. Data taken on the injection lock efficiency over varying seed laser power in the system, current supplied to the seed laser diode, and laser diode temperature confirm that there is a large dependence upon each of these settings. An optimal combination of seed laser diode temperature and current supplied to it can be found to provide an efficient and stable power source for the atomic trap.
We report an efficient trapping of rare-earth-metal Yb atoms with a high-power violet laser diode (LD). An injection-locked violet LD with a 25-mW frequency-stabilized output was used for the magneto-optical trapping (MOT) of fermionic as well as bosonic Yb isotopes. A typical number of $4\ifmmode\times\else\texttimes\fi{}{10}^{6}$ atoms for 174Yb{}^{174}\mathrm{Yb}174Yb with a trap density of $\ensuremath{\sim}1\ifmmode\times\else\texttimes\fi{}{10}^{8}{\mathrm{cm}}^{\ensuremath{-}3}$ was obtained. A 10-mW violet external-cavity LD was used for the one-dimensional slowing of an effusive Yb atomic beam without a Zeeman slower resulting in a 35-fold increase in the number of trapped atoms. The overall characteristics of our compact violet MOT, e.g., the loss time of 1 s, the loading time of 400 ms, and the cloud temperature of 0.7 mK, are comparable to those in previously reported violet Yb MOTs, yet with a greatly reduced cost and complexity of the experiment.
The aim of this research is to pave the way for making a trap for cold neutral atoms based on the force generated by pulses of a mode-locked laser. As an onset towards such a trap we decided to use a far-off-resonance trap (FORT) loaded with cold rubidium atoms from a magneto-optical trap (MOT). Our FORT setup consists of a titanium-sapphire laser that can operate both in continuous wave mode and in mode-locked mode. Our MOT setup uses a magnetic field gradient, and two diode lasers whose frequency is locked very accurately to the atomic transition using polarisation spectroscopy. Since the measurements we do require very precise timing of the order of less than one millisecond between the various phases of the experiment, a time-sequencing program was developed. Using this sophisticated setup, several characteristics of FORTs made with continuous and pulsed lasers were analysed. For example, we have investigated the loading behaviour of the traps and found that under general circumstances there is no significant difference. However, under special conditions it is possible to load more atoms into a pulsed trap. The lifetime of the number of atoms in the trap shows no dependence on the power of the trap laser in the continuous case. For the pulsed trap, however, the increased scattering due to the high peak intensities of the pulses does limit the achievable lifetimes. Moreover, due to the presence of a large number of photoassociation lines, i.e. lines were loosely bound molecules are formed by the interaction of two atoms an a photon, the two-particle losses depend heavily on the wavelength of the trap laser. Furthermore we have done measurements of the temperature of the trapped atoms, which revealed that the temperature is a constant fraction of the trap depth. We also looked at the effects of parametric excitation of the atoms in the FORT. The anharmonicity of the trap formed by the titanium-sapphire laser results in interesting physics, including a change in the average temperature of the atoms, depending on the modulation frequency. We also investigated the trapping behaviour of the FORT at low pulse repetition rates by switching the laser intensity on and off on a kHz scale. We investigated the dependence of the number of atoms on the polarisation of the FORT laser light, both for continuous and pulsed traps. Atoms can be trapped at elliptical polarisations as well, although the number of trapped atoms is less. As the laser is detuned further to the red of the rubidium D line, this effect becomes less and less pronounced, as predicted by our model.