title: Research on beam characteristics in a large-Fresnel-number unstable-waveguide hybrid resonator with parabolic mirrors.
abstract: Large-Fresnel-number unstable-waveguide hybrid resonators employing spherical resonator mirrors suffer from spherical aberration, which adversely affects beam quality and alignment sensitivity. In this paper, we present experimental and numerical wave-optics simulations of the beam characteristics of a negative-branch hybrid resonator having parabolic mirrors with a large equivalent Fresnel number in the unstable direction. These results are compared with a resonator using spherical mirrors. Using parabolic mirrors, the output beam has a smaller beam spot size and higher power density at the focal plane. We found that the power extraction efficiency is 3.5% higher when compared with a resonator using spherical mirrors as the cavity length was varied between -1 and 1 mm from the ideal confocal resonator. In addition, the power extraction efficiency is 5.6% higher for mirror tilt angles varied between -6 and 6 mrad. Furthermore, the output propagating field is similar to a converging wave for a spherical mirror resonator and the output beam direction deviates 3.5 mrad from the optical axis. The simulation results are in good agreement with the experimental results.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Yingxiong
authors.initials: Y
authors.lastname: Qin
authors.forename: Yu
authors.initials: Y
authors.lastname: Xiao
authors.forename: Lijing
authors.initials: L
authors.lastname: Zhong
authors.forename: Chao
authors.initials: C
authors.lastname: Wu
authors.forename: Zhen
authors.initials: Z
authors.lastname: Wang
authors.forename: Wen
authors.initials: W
authors.lastname: Wan
authors.forename: Xiahui
authors.initials: X
authors.lastname: Tang