Two-photon spectroscopy of the 6S(1/2) ? 6D(5/2) transition of trapped atomic cesium

Hyperfine coupling constants of the cesium 7D5/2 state measured up to the octupole term

We report the measurement of hyperfine splitting (HFS) in the 7D_5/2 state of ¹³³Cs using high-resolution Doppler-free two-photon spectroscopy enabled by precise frequency scans using an acousto-optic modulator (AOM). All six hyperfine levels are resolved in our spectra. We determine the hyperfine coupling constants A = -1.70867(62) MHz and B = 0.050(14) MHz which represent an over 20-times improvement in the precision of both A and B. Moreover, our measurement is sufficiently precise to put bounds on the value of the magnetic octupole coupling constant C = 0.4(1.4) kHz for the 7D_5/2 state. We additionally report the measurement of the ac Stark shift [-46 ± 4 Hz/(W/cm²)], collisional shift, and pressure broadening which are important for optical frequency standards based on the 6S_1/2 → 7D_5/2 two-photon transition.

Doubly Magic Optical Trapping for Cs Atom Hyperfine Clock Transitions

We analyze doubly magic trapping of Cs hyperfine transitions including previously neglected contributions from the ground state hyperpolarizability and the interaction of the laser light and a static magnetic field. Extensive numerical searches do not reveal any doubly magic trapping conditions for any pair of hyperfine states. However, including the hyperpolarizability reveals light intensity insensitive traps for a wide range of wavelengths at specific intensities. We then investigate the use of bichromatic trapping light fields. Deploying a bichromatic scheme, we demonstrate doubly magic red and blue detuned traps for pairs of states separated by one or two single photon transitions.

Observation of rubidium 5S1/2 --> 7S1/2 two-photon transitions with a diode laser

The 5S1/2 --> 7S1/2 two-photon transition of atomic rubidium, which is 100 times weaker than the 5S-5D transition, is observed with an extended-cavity diode laser and a vapor cell. Signals with a signal-to-noise ratio of 280 are obtained with a laser power of 10 mW, and the observed linewidth is 3 MHz. The laser wavelength is 760 nm and is locked on the transitions to a stability of 2 x 10(-11). For the first time to our knowledge, the isotope shift of this transition is measured to be 130(4) MHz in atomic frequency.

Nonlinear absorption by quantum interference in cold atoms

We report an experimental observation of third-order nonlinear absorption by quantum interference in (87)Rb atoms cooled and confined in a magneto-optic trap. A coupling laser creates electromagnetically induced transparency (EIT) in a multilevel Rb system in which the third-order nonlinear absorption is enhanced by constructive quantum interference while the linear absorption is inhibited by destructive interference. Our experiment demonstrates the EIT system proposed by Harris and Yamamoto [Phys. Rev. Lett. 81, 3611 (1998)], which absorbs two photons but not one photon in the dressed-state picture.

Spectroscopy on a modulated magneto-optical trap

We demonstrate a new type of high-resolution two-photon frequency modulation (FM) spectroscopy with cold atoms in a magneto-optical trap. Instead of modulating the probe as in ordinary FM spectroscopy, we modulate the trap itself by FM of the trapping beams. We present theoretical as well as experimental results for both absorption and polarization rotation spectroscopy. Finally, we demonstrate two-photon FM spectroscopy, using the intrinsic phase noise of the trapping diode lasers.

7S(1/2) ? 9S(1/2) two-photon spectroscopy of trapped francium

We report on the spectroscopic measurement of the (210)Fr 9S(1/2) energy obtained by two-photon excitation of atoms confined and cooled in a magneto-optic trap. The resonant intermediate level 7P(3/2) is the upper state of the trapping transition. We have measured the energy difference between the 9S(1/2) state and the 7S(1/2) ground state to be 25 671.021 +/- 0.006 cm(-1).

Frequency metrology by use of quantum interference

Quantum interference in the rate of two-photon excitation of the 6S((1/2)) ?6P(3/2) ? 6D(5/2) transition in atomic cesium is exploited to demonstrate phase-sensitive frequency demodulation for an optical interval of +/- 12.5 THz. By thus using atoms as ultrafast nonlinear mixing elements, we suggest and analyze a new avenue for absolute comparisons of a dense set of frequencies over the range of 200-2000 nm.

Magneto-optic trap of Rb atoms with an injection-seeded laser that operates at two frequencies

We captured Rb atoms in a magneto-optic trap by using two frequencies in an injection-seeding process of a diode laser without the use of a separate repumping laser. In the incomplete injection-seeding condition, the power of the free-running slave laser at the repumping frequency can be partially converted into power at the master laser frequency, which is stabilized at the cooling frequency. We measured conversion efficiencies and frequency shifts based on the injecting power and the preset frequency difference between the master laser and the slave laser.