Lateral displacement of the mode axis in a misaligned Porro prism resonator.
The lateral shift of the mode axis in a misaligned Porro prism resonator is analyzed. A method to find the tilted mode axis in a misaligned Porro prism resonator is introduced. Expressions for the displacement of the mode axis are deduced. They predict that the lateral displacement of the mode axis is proportional to the horizontal misalignment angle beta and highly dependent of the prism azimuth angle theta. Experimental results obtained agree well with theory.
Roof-mirror resonators
Modes, losses, and phase shift are determined for an open resonator formed by two equal and symmetric roof mirrors with roof angle α ranging from −8° to 100°. In all cases, the Fresnel number of the resonator was N = 1 and the mirror spacing L = 100λ. The results of the numerical analysis show two stability regions that correspond to quasi-flat-roof resonators and to quasi-90° roof resonators, respectively. The equivalence between a resonator with a small roof angle α (quasi-flat roof) and a resonator with roof angle (π + α)/2 is discussed. A quasi-90° roof resonator presents losses generally smaller than the equivalent flat-roof resonator.
Dihedral optical resonators and prism beam waveguides.
A simple theory is developed for optical resonators, in which the mirrors are each composed of two planes forming a nearly straight dihedral angle and an equivalent beam-waveguide comprising a sequence of narrow angle prisms. Geometric optical considerations yield the variation of the intensity within the resonator in a manner analogous to (although not entirely as satisfying as in) the case of the spherical mirror resonator. Modes of the continuous medium, identified as the limit of particular sequences of closely spaced weak prisms, characterized by a parameter Omega, are found in terms of Airy functions. An appropriate spot size parameter is given by [Omega/2k0(2)]1/3, where k(0) is the wavenumber.