In this dissertation we report the results of two experimental projects with laser-cooled

rubidium atoms: I. Application of Bessel beams for atom optics, and II.

Spectroscopic measurements of Rydberg blockade effect.

The first part of the thesis is devoted to the development of new elements of

atom optics based on blue-detuned high-order Bessel beams. Properties of a 4th order

Bessel beam as an atomic guide were investigated for various parameters of

the hollow beam, such as the detuning from an atomic resonance, size and the

order of the Bessel beam. We extended its application to create more complicated

interferometer-type structures by demonstrating a tunnel lock, a novel device that

can split an atomic cloud, transport it, delay, and switch its propagation direction

between two guides. We reported a first-time demonstration of an atomic beam

switch based on the combination of two crossed Bessel beams. We achieved the 30%

efficiency of the switch limited by the geometrical overlap between the cloud and

the intersection volume of the two tunnels, and investigate the heating processes

induced by the switch. We also showed other applications of crossed Bessel beams, such as a 3-D optical trap for atoms confined in the intersection volume of two

hollow beams and a splitter of the atomic density.

The second part of this dissertation is devoted to the spectroscopic measurements

of the Rydberg blockade effect, a conditional suppression of Rydberg excitations

depending on the state of a control atom. We assembled a narrow-linewidth,

tunable, frequency stabilized laser system at 480 nm to excite laser-cooled rubidium

atoms to Rydberg states with a high principal quantum number n ~ 50 through a

two-photon transition. We applied the laser system to observe the Autler-Townes

splitting of the intermediate 5p state and used the broadening of the resonance

features to investigate the enhancement of Rydberg-Rydberg interactions in the

presence of an external electric field.