We present and analyze a method of laser frequency stabilization via steady-state patterns of spectral-holes in Eu3+:Y2SiO5. Three regions of holes are created, spaced in frequency by the ground state hyperfine splittings of 151Eu3+ . The absorption pattern of the holes is shown not to degrade after days of probe laser stabilization. An optical frequency comparison between a laser locked to such a steady-state spectral-hole pattern, an independent cavity-stabilized laser, and a Yb optical lattice clock demonstrates a spectral-hole frequency stability of 1x10-15tau-1/2 that averages to 8.5 (+4.8 -1.8) x 10-17 at tau = 73 s. Residual amplitude modulation is reduced by an active servo that feeds back to the DC offset of the RF drive applied to the fiber coupled electro-optic modulator to less than 1x10-6 fractional amplitude modulation at tau > 1 s. The contribution of residual amplitude modulation to the laser frequency instability is further reduced by digital division of the transmission and incident photodetector signals to less than 1x10-6 at tau > 1 s.
Physical Review Letters
laser frequency stabilization, spectral hole burning, spectral diffusion, residual amplitude modulation