Dual-Wavelength Ultra-Stable Optical Cavity

We present the development of a dual-wavelength ultra-stable optical cavity operating at 1064 nm and 908 nm – the wavelengths that, after frequency quadrupling, correspond to Hg clock transitions at 266 nm (
¹
S
0
-
³
P
0
) and 227 nm (
¹
S
0
-
³
P
2
). The cavity will be applied for precise spectroscopic measurements of clock lines of Hg atoms.