A highly stable monolithic enhancement cavity for second harmonic generation in the ultraviolet

We present a highly stable bow-tie power enhancement cavity for critical second harmonic generation (SHG) into the UV using a Brewster-cut β-BaB2O4 (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 h uninterrupted operation without decay in output power at 313 nm. The robustness of the system has been confirmed by exposing it to accelerations of up to 1 g with less than 10% in-lock output power variations. Furthermore, the cavity can withstand 30 min of acceleration exposure at a level of 3 grms without substantial change in the SHG output power, demonstrating that the design is suitable for transportable setups. © 2018 Author(s)

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

We present a highly stable bow-tie power enhancement cavity for critical second-harmonic generation into the UV using a Brewster-cut $\beta$-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