Response of two-level atoms to intense amplitude modulated laser beams

Surya P. Tewari, Manisha Kumari

Stanislav D. Tvorogov, Vitaly Fedoseev, К. Н. Югай

Heung‐Ryoul Noh, Sang Eon Park

Barbara Blind, P. Fontana, P Thomann

The spectrum of light scattered by a two-level atom in an intense laser beam with amplitude modulated light is calculated. The spectrum is obtained by evaluating the Fourier transform of the autocorrelation function of the dipole moment. The modulation introduces new components in both the coherent and incoherent parts of the frequency distribution. The total intensity when plotted as a function of the average Rabi frequency exhibits parametric resonances.

Vladimir Leonardovich Derbov, Inna L. Plastun

On-resonance self-action of a beam with periodically modulated amplitude in a two-level saturable absorber is studied numerically. When the period of modulation is comparable with relaxation times, one cannot describe the medium by means of susceptibility, and the response of the medium to the amplitude variation is not immediate. We solve the Bloch equations in each point of the medium to find this response correctly. Transient behavior followed by stable oscillations of population difference and polarization vector is shown to depend strongly on the frequency and amplitude of modulation. Beam propagation is considered using a simplified model of a thin absorber followed by free space, the propagation distance being small compared with the modulation wavelength. Manifestations of non-stationary response of the medium in the output intensity behavior are analyzed.

Stephanos Papademetriou, Stephen H. Chakmakjian, Carlos R. Stroud

The interaction of a strong bichromatic field with a two-level atom has been the subject of numerous experimental and theoretical investigations. We performed an experimental study of the Interaction of an intense 100% amplitude-modulated (AM) field with an ensemble of homogeneously broadened two-level atoms. An optically pumped sodium atomic beam is used as the atomic medium. The field is created by interfering two intense frequency-stabilized laser fields. The frequency of one field is held fixed while another field of equal amplitude is scanned in frequency. The beat frequency produced by interfering the two laser fields is equal to twice the modulation frequency of a 100% AM field. We monitor the time-averaged fluorescent intensity of the atoms as the frequency separation between the two fields is varied. A similar experiment was done in the past in the rf regime.1 For the first time, we report the observation of multiple, well-resolved resonances in the absorption spectrum of the field in the optical regime. We present data and theory for several values of detuning between the fixed field and atomic resonance. The experimental results are in good agreement with theory.