The Suppressed Cavity-Pulling Effect in Dual-Wavelength Active Optical Clock Based on Twice Cavty-Locking Technique

We have proposed a new scheme for the realization of an excellent active optical frequency standard by utilizing fast and slow twice cavity-locking technique in dual-wavelength active optical clock. The performance is expected to achieve the short term stability of $3.8\times 10^{-16}$ at 1 s and long-term stability of 10−18 magnitude. Also, the linewidth is expected to reach the quantum limited linewidth with the frequency shift of $7.1\times 10^{-5} \text{Hz}/\mathrm{s}$. The system includes four main technologies: dual-wavelength active optical clock, Pound-Drever-Hall technique, phase-stabilized femtosecond laser comb and high speed feedback technique. The cavity length is relocked through slow and fast feedback to two piezoelectric translators of the main-cavity. Therefore, the residual cavity-pulling effect influencing the long-term frequency stability in four-level active optical clock can be suppressed by square times of the bad-cavity coefficient. The frequency stability and the frequency shift of the active optical frequency standard are expected to be two orders and four orders of magnitude better than the ultra-stable reference cavity laser, respectively.