Polarization instability of ring lasers

C. A. Schrama, Martijn A. van Eijkelenborg, J. P. Woerdman +1 more

Mark D. Matlin, R. S. Gioggia, N. B. Abraham +2 more

M. Arjona, R. Corbalán, Ferran Laguarta +2 more

The dynamic behavior of a coherently pumped ring laser with a homogeneously broadened four-level medium is analyzed theoretically, considering linearly polarized pump and generated laser beams. The laser is shown to be much more stable when these polarizations are parallel than when they are orthogonal. In the latter case the instability pump threshold can be as low as four times the first laser threshold, and the laser dynamics shows Lorenz-type features.

N. B. Abraham, E. Arimondo, Maxi San Miguel

Andrea Li Bassi, Franco Prati, Luigi A. Lugiato

We start from the Maxwell-Bloch equations that govern the dynamics of Fabry-Perot lasers and, considering a doubled cavity, generalize our traveling wave formalism to the case in which the two-level medium does not fill the cavity but occupies only a portion of it. We linearize these equations and focus on the adiabatic elimination of both atomic fluctuations. Next, we restrict our attention to free running lasers under resonant conditions and analyze amplitude and phase instabilities. The examination of the unstable domain leads to the conclusion that the multimode Fabry-Perot instability arises near threshold only when the ratio of the longitudinal to the transverse atomic relaxation rate is substantially smaller than unity. This result agrees with our previous study in the limit of adiabatic elimination of the atomic polarization fluctuations only. We describe the self-pulsing behavior that arises from the multimode instability, and exhibits hysteretic behavior when the pump parameter is swept forward and backward. Finally, we investigate the single-mode instability and show that in the Fabry-Perot case there is no longer the correspondence between single-mode and multimode instabilities that is well known in the case of ring lasers. We confirm that in the case of resonant Fabry-Perot lasers the single-mode amplitude instability arises very far from threshold.

E. M. Pessina, Franco Prati, Javier Redondo +2 more

We analyze the conditions under which the Risken-Nummedal-Graham-Haken multimode instability can be observed in ring-cavity class-B three- and four-level lasers. Relevant examples of these are rare-earth doped fiber lasers. We show that the standard two-level laser model can be applied to three- and four-level laser systems under quite general conditions. We take advantage of this isomorphism to derive the conditions for the observation of the instability. The analysis is extended to the case in which the uniform field limit does not apply in order to cover more realistic situations.