title: Ultrafast optical control of group delay of narrow-band terahertz waves.
abstract: We experimentally demonstrate control over the group delay of narrow-band (quasi continuous wave) terahertz (THz) pulses with constant amplitude based on optical switching of a metasurface characteristic. The near-field coupling between resonant modes of a complementary split ring resonator pair and a rectangular slit show an electromagnetically induced transparency-like (EIT-like) spectral shape in the reflection spectrum of a metasurface. This coupling induces group delay of a narrow-band THz pulse around the resonant frequency of the EIT-like spectrum. By irradiating the metasurface with an optical excitation pulse, the metasurface becomes mirror-like and thus the incident narrow-band THz pulse is reflected without a delay. Remarkably, if we select the appropriate excitation power, only the group delay of the narrow-band THz pulse can be switched while the amplitude is maintained before and after optical excitation.
authors.affiliation: Department of Physics, Faculty of Science, Shinshu University, 3-1-1 Asahi, Matsumoto, Nagano, Japan.
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Miyamaru
authors.affiliation: Department of Physics, Faculty of Science, Shinshu University, 3-1-1 Asahi, Matsumoto, Nagano, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Morita
authors.affiliation: Department of Physics, Faculty of Science, Shinshu University, 3-1-1 Asahi, Matsumoto, Nagano, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Nishiyama
authors.affiliation: Department of Physics, Faculty of Science, Shinshu University, 3-1-1 Asahi, Matsumoto, Nagano, Japan.
authors.forename: Tsubasa
authors.initials: T
authors.lastname: Nishida
authors.affiliation: Department of Electronic Science and Engineering, Kyoto University, Kyoto, Japan.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Nakanishi
authors.affiliation: Department of Electronic Science and Engineering, Kyoto University, Kyoto, Japan.
authors.forename: Masao
authors.initials: M
authors.lastname: Kitano
authors.affiliation: Department of Physics, Faculty of Science, Shinshu University, 3-1-1 Asahi, Matsumoto, Nagano, Japan.
authors.forename: Mitsuo W
authors.initials: MW
authors.lastname: Takeda