[19p-431B-1~18] 3.5 Laser system and materials

[19p-431B-12] Thermal lens effect in Input Mode Cleaner of the gravitational-wave detector KAGRA

〇Issei Sugai¹, Masashi Ohkawa², Kentaro Somiya³, Seiji Kawamura⁴, Keiko Kokeyama⁵, Takamasa Suzuki¹, Takashi Sato² (1.Grad. School of Sci. and Tech., Niigata Univ., 2.Fac. of Eng., Niigata Univ., 3.Dept. of Phys., Tokyo Tech., 4.Grad. School of Sci., Nagoya Univ., 5.ICRR, Univ. of Tokyo)

Keywords:thermal lens effect, gravitational wave detector, KAGRA

A Japanese gravitational-wave antenna, called KAGRA, is a 3-km Michelson-type laser interferometer to detect gravitational waves. In the input optics system of the KAGRA, the input mode cleaner (IMC) plays important roles to stabilize the pre-stabilized laser beam in TEM₀₀ mode content and position. Since the IMC is a three-mirror triangular ring cavity, power density in the IMC is extremely high due to resonance. The high power density can bring unnecessary heating, which causes thermal lens effect, to the mirrors. So, in this study, influence of the thermal lensing on transmitted light from the IMC was considered by numerical simulation using FINESSE.