Nonlinear interaction of laser modes

William R. Green

Daniel S. Elliott

A number of experimental investigations have been carried out over the past fifteen years which have been used to study the effect of the bandwidth of the laser on various nonlinear optical interactions. These are useful and interesting for a number of reasons. On the technical side laser bandwidth effects can limit the accuracy of measurements of the frequency of atomic transitions as well as the determination of the strength of the interaction. Of a more fundamental interest is the question of the behavior of the nonlinear atomic system when interacting with the non-monochromatic field. In the first experiments carried out to investigate these effects lasers were used which could be operated on a single longitudinal mode or on multiple modes corresponding to the presence or absence of an intra-cavity etalon. Following this a number of techniques were developed to modulate the amplitude phase and/or frequency of the output of a stabilized cw laser with a random (but well-characterized) signal. In this way laser fields could be generated in the laboratory which closely approximate models of laser fields on which theorists have based calculations of laser bandwidth effects. These works allow direct quantitative comparison of results with theory. A number of these field models which can now be generated in the laboratory will be discussed as well as measurements of the role they play in nonlinear interactions.

P G Eliseev

The spectral perturbation is considered in a semiconductor active medium in the vicinity of the frequency of a strong electromagnetic wave. The nonlinear interaction of waves via the dynamic interference grating, or nonlinear scattering by population waves leads to the shift of resonance frequencies, which is manifested, in particular, in a change of the mode-beating spectrum of the laser. The spectral profile of this perturbation depends on the amplitude—phase coupling factor α. For large α, the profile becomes symmetrical in detuning from the strong-mode frequency. A change in the group refractive index corresponding to the 'slowing' of light is also calculated.

L. Lynds, Albert W. Angelbeck, B. Burdick

R. Kh. Gainutdinov, Aigul A. Mutygullina

We show that for some intensities of a driving laser field not only the laser modes but also the vacuum ones are involved into the strong atom-laser interaction and this has a significant effect on processes of resonance fluorescence.

K. Kaufmann, Wolfgang Weidlich