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arXiv · 1709.07188

A highly stable monolithic enhancement cavity for SHG generation in the UV

S. Hannig·J. Mielke·J. A. Fenske·M. Misera·N. Beev·C. Ospelkaus·P. O. Schmidt
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Abstract

We present a highly stable bow-tie power enhancement cavity for critical second-harmonic generation into the UV using a Brewster-cut $β$-BaB$_2$O$_4$ (BBO) nonlinear crystal. The cavity geometry is suitable for all UV wavelengths reachable with BBO and can be modified to accommodate anti-reflection coated crystals, extending its applicability to the entire wavelength range accessible with non-linear frequency conversion. The cavity is length-stabilized using a fast general purpose digital PI controller based on the open source STEMlab 125-14 (formerly Red Pitaya) system acting on a mirror mounted on a fast piezo actuator. We observe $130\,\mathrm{h}$ uninterrupted operation without decay in output power at $313\,\mathrm{nm}$. The robustness of the system has been confirmed by exposing it to accelerations of up to $1\,\mathrm{g}$ with less than $10\%$ in-lock output power variations. Furthermore, the cavity can withstand 30~minutes of acceleration exposure at a level of $3\,\mathrm{g}_\mathrm{rms}$ without substantial change in SHG output power, demonstrating that the design is suitable for transportable setups.

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S. Hannig, J. Mielke, J. A. Fenske, M. Misera, N. Beev, C. Ospelkaus, P. O. Schmidt. 2017-09-21. A highly stable monolithic enhancement cavity for SHG generation in the UV. https://doi.org/10.1063/1.5005515

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