Input optics systems of the KAGRA detector during O3GK
Authors: Akutsu T , Ando M , Arai K , Arai Y , Araki S , Araya A , Aritomi N , Asada H , Aso Y , Bae S , Bae Y , Baiotti L , Bajpai R , Barton M A , Cannon K , Cao Z , Capocasa E , Chan M , Chen C , Chen K , Chen Y , Chiang C-I , Chu H , Chu Y-K , Eguchi S , Enomoto Y , Flaminio R , Fujii Y , Fujikawa Y , Fukunaga M , Fukushima M , Furuhata T , Gao D , Ge G-G , Ha S , Hagiwara A , Haino S , Han W-B , Hasegawa K , Hattori K , Hayakawa H , Hayama K , Himemoto Y , Hiranuma Y , Hirata N , Hirose E , Hong Z , Hsieh B-H , Huang G-Z , Huang H-Y , Huang P , Huang Y-C , Huang Y-J , Hui D C Y , Ide S , Ikenoue B , Imam S , Inayoshi K , Inoue Y , Ioka K , Ito K , Itoh Y , Izumi K , Jeon C , Jin H-B , Jung K , Jung P , Kaihotsu K , Kajita T , Kakizaki M , Kamiizumi M , Kanbara S , Kanda N , Kang G , Kataoka Y , Kawaguchi K , Kawai N , Kawasaki T , Kim C , Kim J , Kim J C , Kim W S , Kim Y-M , Kimura N , Kita N , Kitazawa H , Kojima Y , Kokeyama K , Komori K , Kong A K H , Kotake K , Kozakai C , Kozu R , Kumar R , Kume J , Kuo C , Kuo H-S , Kuromiya Y , Kuroyanagi S , Kusayanagi K , Kwak K , Lee H K , Lee H W , Lee R , Leonardi M , Li K L , Lin L C-C , Lin C-Y , Lin F-K , Lin F-L , Lin H L , Liu G C , Luo L-W , Majorana E , Marchio M , Michimura Y , Mio N , Miyakawa O , Miyamoto A , Miyazaki Y , Miyo K , Miyoki S , Mori Y , Morisaki S , Moriwaki Y , Nagano K , Nagano S , Nakamura K , Nakano H , Nakano M , Nakashima R , Nakayama Y , Narikawa T , Naticchioni L , Negishi R , Quynh L Nguyen , Ni W-T , Nishizawa A , Nozaki S , Obuchi Y , Ogaki W , Oh J J , Oh K , Oh S H , Ohashi M , Ohishi N , Ohkawa M , Ohta H , Okutani Y , Okutomi K , Oohara K , Ooi C , Oshino S , Otabe S , Pan K-C , Pang H , Parisi A , Park J , Arellano F E Peña , Pinto I , Sago N , Saito S , Saito Y , Sakai K , Sakai Y , Sakuno Y , Sato S , Sato T , Sawada T , Sekiguchi T , Sekiguchi Y , Shao L , Shibagaki S , Shimizu R , Shimoda T , Shimode K , Shinkai H , Shishido T , Shoda A , Somiya K , Son E J , Sotani H , Sugimoto R , Suresh J , Suzuki T , Suzuki T , Tagoshi H , Takahashi H , Takahashi R , Takamori A , Takano S , Takeda H , Takeda M , Tanaka H , Tanaka K , Tanaka K , Tanaka T , Tanaka T , Tanioka S , Tapia San Martín E N , Telada S , Tomaru T , Tomigami Y , Tomura T , Travasso F , Trozzo L , Tsang T , Tsao J-S , Tsubono K , Tsuchida S , Tsutsui T , Tsuzuki T , Tuyenbayev D , Uchikata N , Uchiyama T , Ueda A , Uehara T , Ueno K , Ueshima G , Uraguchi F , Ushiba T , Putten M H P M , Vocca H , Wang J , Washimi T , Wu C , Wu H , Wu S , Xu W-R , Yamada T , Yamamoto K , Yamamoto K , Yamamoto T , Yamashita K , Yamazaki R , Yang Y , Yano K , Yokogawa K , Yokoyama J , Yokozawa T , Yoshioka T , Yuzurihara H , Zeidler S , Zhan M , Zhang H , Zhao Y , Zhu Z-H , Goetz R , Heintze M , Liu J , Müller C , Savage R L , Tanner D B 
Published: December 2022

Abstract
KAGRA, the underground and cryogenic gravitational-wave detector, was operated for its solo observation from February 25 to March 10, 2020, and its first joint observation with the GEO 600 detector from April 7 to April 21, 2020 (O3GK). This study presents an overview of the input optics systems of the KAGRA detector, which consist of various optical systems, such as a laser source, its intensity and frequency stabilization systems, modulators, a Faraday isolator, mode-matching telescopes, and a high-power beam dump. These optics were successfully delivered to the KAGRA interferometer and operated stably during the observations. The laser frequency noise was observed to limit the detector sensitivity above a few kilohertz, whereas the laser intensity did not significantly limit the detector sensitivity.