Abstract: An improved design of Faraday Optical Isolator at 780nm is developed. Numerical simulation is used to confirm the design. It has advantage of more uniform magnetic field, smaller size and better isolation. This design of magnet called style “π” divides a whole hollow cylinder into 3 parts including several fan-shaped magnets. It can increase the use ratio of the remanence of magnet. The design of one-stage isolator has a volume of 52cm3 with a volume of magnet of 18cm3, which is small. The optical clear aperture is 5mm with a 34.6-dB isolation and 90.9% transmission rate. Style “II” may also be optional for having a smaller volume but less uniformed magnets. The isolator developed according to style “π” has better performance than common used optical isolators in terms of atomic, molecular and optics (AMO) physics at the special wavelength of 780nm in order to meet the demands of the ultracold atom system.

Key words: Laser devices; Faraday optical isolator; Numerical simulation; Bose-Einstein condensation; Cold atom