Frequency stabilization of Nd:YAG lasers with a most probable linewidth of 06 Hz

Two Nd:YAG lasers at 1064 nm are independently frequency-stabilized to two separately located, vertically mounted ultrastable Fabry–Perot reference cavities. Measurements show that each laser system has achieved a most probable linewidth of 0.6 Hz and fractional frequency instability of ∼1.2×10−15 between 1 and 40 s averaging time. Systematic evaluation shows that the performance of each laser system is limited by thermal noise of the reference cavity.