title: Measurement of beam profiles by terahertz sensor card with cholesteric liquid crystals.
abstract: We demonstrate a sensor card with cholesteric liquid crystals (CLCs) for terahertz (THz) waves generated from a nonlinear crystal pumped by a table-top laser. A beam profile of the THz waves is successfully visualized as color change by the sensor card without additional electronic devices, power supplies, and connecting cables. Above the power density of 4.3  mW/cm2, the approximate beam diameter of the THz waves is measured using the hue image that is digitalized from the picture of the sensor card. The sensor card is low in cost, portable, and suitable for various situations such as THz imaging and alignment of THz systems.
authors.forename: Yuzuru
authors.initials: Y
authors.lastname: Tadokoro
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Nishikawa
authors.forename: Boyoung
authors.initials: B
authors.lastname: Kang
authors.forename: Keisuke
authors.initials: K
authors.lastname: Takano
authors.forename: Masanori
authors.initials: M
authors.lastname: Hangyo
authors.forename: Makoto
authors.initials: M
authors.lastname: Nakajima