A Mode Cleaner Cavity for Improved Stability of an Optical Dipole Trap

The use of optical dipole traps has become a standard technique to trap ultracold atoms. Generated by a focused, far-detuned laser beam, our single-beam optical dipole trap is intended to be a strictly TEM$_{00}$ mode, as the presence of higher order modes can introduce instabilities in the trap. In particular, the location of the laser beam focus can vary over time when higher-order modes are present. We implement a monolithic mode cleaner cavity designed to pass the TEM$_{00}$ mode and suppress higher-order transverse modes. The cavity consists of four mirrors in a bow-tie configuration and is locked on resonance by using the tilt locking method\footnote{D. Shaddock, M. Gray, and D. McClelland, Opt. Lett. 24, 1499-1501 (1999).}. We characterize the performance of the cavity and its effect in improving the stability of an optical dipole trap used in experiments with bright matter-wave solitons.