Modal instability suppression in a high-average-power and high-finesse Fabry-Perot cavity.

An experimental method to remove modal instabilities induced by thermoelastic deformation in optical high-finesse resonators is presented and experimentally investigated in this paper. The method is found suitable for multi-mirror folded monolithic and compact cavities, such as those used in the particle accelerator environment. It is also suitable for very high stacked average power. Here we demonstrate stable operation at the 200 kW intracavity average power.

Polarization induced instabilities in external four-mirror Fabry-Perot cavities.

Various four-mirror optical resonators are studied from the perspective of realizing passive stacking cavities. A comparative study of the mechanical stability is provided. The polarization properties of the cavity eigenmodes are described, and it is shown that the effect of mirror misalignments (or motions) induces polarization and stacking power instabilities. These instabilities increase with the finesse of the Fabry-Perot cavity. A tetrahedral configuration of the four mirrors is found to minimize the consequences of the mirrors' motion and misalignment by reducing the instability parameter by at least 2 orders of magnitude.

On the nonparaxial modes of two-dimensional nearly concentric resonators.

A nonparaxial scalar diffraction integral is used to determine numerically the resonance modes of a two-dimensional nearly concentric Fabry-Perot resonator. Numerical examples are provided, and results are compared to those published by Laabs and Friberg [IEEE J. Quantum Electron. 35, 198 (1999)]. Discrepancies are reported and further discussed on the basis of the difference between the solution space supported by the numerical method used here and the one used by Laabs and Friberg.