Precision optomechanics for geometrically modematched Fabry-Perot cavities in ALPS II

Challenging optical resonant gain achieved via the use of two geometrically modematched Fabry-Perot cavities is anticipated in Any Light Particle Search II (ALPS II) to extend the search sensitivity of light-weight sub-eV dark matter candidates to uncharted parameter space of scientific interest. We report on the precision optomechanics developed for geometrical modematching of optical cavities. The general concept, the mechanical mounting scheme, and the use of an autocollimator to streamline the metrology procedure are rigorously examined using optical interferometry, all of which meet the requirements of ALPS II.