Femtosecond enhancement cavity with kilowatt average power

Zhang Jin^{1, 2}, Hua Lin-Qiang^{1, †}, Yu Shao-Gang^{1, 2}, Chen Zhong^{1, 2}, Liu Xiao-Jun^{1, ‡}

(a) PDH error signal and the intensity of transmission when the length of the cavity is slowly swept. (b) After locking, the intensity of transmission maintains maximum and the PDH error signal becomes a flat line.