arXiv subjects

Umakant D. Rapol

Publications and source records attributed to Umakant D. Rapol.

24 records · Page 2Linked to original sources

arXiv2002

Observation of sub-natural linewidths for cold atoms in a magneto-optic trap

We have studied the absorption of a weak probe beam through cold rubidium atoms in a magneto-optic trap. The absorption spectrum shows two peaks with the smaller peak having linewidth as small as 28% of the natural linewidth. The modification happens because the laser beams used for trapping also drive the atoms coherently between the ground and excited states. This creates ``dressed'' states whose energies are shifted depending on the strength of the drive. Linewidth narrowing occurs due to quantum coherence between the dressed states. The separation of the states increases with laser intensity and detuning, as expected from this model.

physics.atom-ph↗

arXiv2002

Frequency locking of tunable diode lasers to a stabilized ring-cavity resonator

We demonstrate a technique for locking the frequency of a tunable diode laser to a ring-cavity resonator. The resonator is stabilized to a diode laser which is in turn locked to an atomic transition, thus giving it absolute frequency calibration. The ring-cavity design has the principal advantage that there is no feedback destabilization of the laser. The cavity has a free-spectral range of 1.3 GHz and $Q$ of about 35, which gives robust locking of the laser. The locked laser is able to track large scans of the cavity.

physics.optics↗

arXiv2002

High-accuracy wavemeter based on a stabilized diode laser

We have built a high-accuracy wavelength meter for tunable lasers using a scanning Michelson interferometer and a reference laser of known wavelength. The reference laser is a frequency stabilized diode laser locked to an atomic transition in Rb. The wavemeter has a statistical error per measurement of 5 parts in $10^7$ which can be reduced considerably by averaging. Using a second stabilized diode laser, we have verified that systematic errors are below 4 parts in $10^8$.

physics.ins-det↗

arXiv2002

Direct measurement of the fine-structure interval in alkali atoms using diode lasers

We demonstrate a technique for directly measuring the fine-structure interval in alkali atoms using two frequency-stabilized diode lasers. Each laser has a linewidth of order 1 MHz and precise tunability: one laser is tuned to a hyperfine transition in the D_1 line, and the other laser to a hyperfine transition in the D_2 line. The outputs of the lasers are fed into a scanning Michelson interferometer that measures the ratio of their wavelengths accurately. To illustrate the technique, we measure the fine-structure interval in Rb, and obtain a value of 237.6000(3)(5) cm^-1 for the hyperfine-free 5P_{3/2} - 5P_{1/2} interval.

physics.atom-ph↗

arXiv2002

Loading of a Rb magneto-optic trap from a getter source

We study the properties of a Rb magneto-optic trap loaded from a commercial getter source which provides a large flux of atoms for the trap along with the capability of rapid turn-off necessary for obtaining long trap lifetimes. We have studied the trap loading at two different values of background pressure to determine the cross-section for Rb--N$_2$ collisions to be 3.5(4)x10^{-14} cm^2 and that for Rb--Rb collisions to be of order 3x10^{-13} cm^2. At a background pressure of 1.3x10^{-9} torr, we load more than 10^8 atoms into the trap with a time constant of 3.3 s. The 1/e lifetime of trapped atoms is 13 s limited only by background collisions.

physics.atom-ph↗

arXiv2002

Sub-natural linewidth in room-temperature Rb vapor using a control laser

We demonstrate two ways of obtaining sub-natural linewidth for probe absorption through room-temperature Rb vapor. Both techniques use a control laser that drives the transition from a different ground state. The coherent drive splits the excited state into two dressed states (Autler-Townes doublet), which have asymmetric linewidths when the control laser is detuned from resonance. In the first technique, the laser has a large detuning of 1.18 GHz to reduce the linewidth to 5.1 MHz from the Doppler width of 560 MHz. In the second technique, we use a counter-propagating pump beam to eliminate the first-order Doppler effect. The unperturbed probe linewidth is about 13 MHz, which is reduced below 3 MHz (0.5 Γ) at a detuning of 11.5 MHz.

physics.atom-ph↗