This paper treats the issue of locking a solid state laser, pumped by high power diodes (Verdi V5), to a twenty meter long optical resonator for OSQAR LSW - light shining through the wall, dark matter search experiment. In this paper the optical design and a possible locking scheme are presented. The environmental conditions in SM18 testing hall at CERN, where OSQAR experiment is based, are discussed. The main focus is put on the vibration analysis, cavity transversal modes behaviour, possible clipping in the anticryostat of LHC – Large Hadron Collider magnet bore and locking loop parameters required for future experimental testing. The expected finesse of resonator will be presented and discussed in the sense of OSQAR LSW; its impact on possible new exclusion limits is discussed.
A sensitive method for optical birefringence measurement is presented. To optimize the signal over the noise ratio, the polarization of the laser beam is modulated exceptionally with a high frequency electro-optical modulator. The specially developed optical apparatus exhibits high sensitivity and accuracy, which were checked by measuring the Cotton-Mouton effect in nitrogen as a function of the pressure. It is able to measure the retardance down to 2x10<sup>-4</sup> rad. This apparatus will be used with the locked optical cavity. The optical cavity will serve as an optical path multiplier for increasing the sensitivity. This proposed set-up will be able to measure the Cotton-Mouton effect in helium, where the birefringence effect is Δn ≈ 2.4x10<sup>-16</sup>.
This paper gives short overview of laser-based experiment OSQAR at CERN which is focused on search of axions and
axion-like particles. The OSQAR experiment uses two experimental methods for axion search – measurement of the
ultra-fine vacuum magnetic birefringence and a method based on the “Light shining through the wall” experiment.
Because both experimental methods have reached its attainable limits of sensitivity we have focused on designing a
vacuum laser resonator. The resonator will increase the number of convertible photons and their endurance time within
the magnetic field. This paper presents an opto-mechanical design of a two component transportable vacuum laser
resonator. Developed optical resonator mechanical design allows to be used as a 0.8 meter long prototype laser resonator
for laboratory testing and after transportation and replacement of the mirrors it can be mounted on the LHC magnet in
CERN to form a 20 meter long vacuum laser resonator.