Frequency shifts of laser modes in solid state and gaseous systems

Paul Mandel

F Ahmad

The semi-classical laser equations are analysed outside the rotating-wave approximation and a new exact steady-state solution for stationary but inhomogeneously broadened atoms is obtained. Results applicable to any solid-state laser are derived and these are also relevant to a gas laser working near threshold or at very high intensities. The resonance frequency exhibits a Bloch-Siegert shift. New results in the theory of frequency pulling and pushing are obtained.

Victor R. Blok, Gennady M. Krochik

We here present the theory of lasing without inversion for systems with a split upper laser level. We show that the effect of amplification without inversion may be realized for at least two different situations. In the first situation, the effect is due to the asymmetry of radiative characteristics of quasidegenerate transitions. In the second situation, the effect can be provided without any asymmetry and is achievable for the definite phase of the transfer of coherence between the quasidegenerate levels (quasiparametric amplification). We also show that for laser amplification without inversion, the rate (frequency) of mixing of the quasidegenerate levels should be significantly higher than the linewidths of these levels. This mixing of quasidegenerate levels can be realized by low-frequency electromagnetic radiation or by interaction with an auxiliary third level. In addition, we derive the conditions for providing laser action for such systems rigorously, and we give some specific examples for the realization of this effect in gaseous and solid-state media. One of the most promising configurations may be realized in solid-state media when two narrow quasidegenerate levels are embedded in quasifree states (low-density state conduction band). We also discuss the use of a parametric mechanism for the creation of spatial gratings and for the construction of new types of electro-optical devices.

Richard M. Friedberg, Sven R. Hartmann, Jamal T. Manassah

Hermann Haken, H. Sauermann

Jian Wu, Heping Zeng

We suggest that subfemtosecond pulses can be generated by using high-order stimulated Raman scattering when a Raman transition is driven by three intense single-mode laser beams with two different modulation frequencies. An oscillatory strong Raman coherence is established by the modulated molecular modulation. Numeric simulations based on the first fundamental vibrational Raman transition of gaseous and solid deuterium indicate that subfemtosecond pulses can be generated by Raman excitations with above, below, or opposite Raman detunings.