[15p-PB01-1~5] 3.8 Terahertz technologies (formerly 3.9)

[15p-PB01-5] Correction of Refractive Indices Obtained by Low-Cost sub-THz Spectrometer at Focus

〇Osamu Morikawa¹, Ai Hattori¹, Kohji Yamamoto², Kazuyoshi Kurihara², Takashi Furuya², Fumiyoshi Kuwashima³, Hideaki Kitahara², Masahiko Tani² (1.JCGA, 2.Univ. Fukui, 3.FUT)

Keywords:THz-TDS, focusing, refractive index

Terahertz time-domain spectroscopic systems (THz-TDSs) are broadly used for sample characterization in the THz region. If one can prepare only a small sample, it must be placed at the focus of the THz beam. In such cases, obtained refractive index is a little bit larger than that obtained by placing large sample with the same material in the parallel beam. Therefore, correction is required. The previously reported correction method is based on the Gouy phase shift at the detector position caused by the sample insertion. However, this correction method assumes that (a) the sample is optically thin, (b) the beam waist shift caused by the sample insertion and Rayleigh length around the beam waist are much smaller than the distance between optics and beam waists, and (c) the detector is EO type without Si hemispherical lenses. In this study, we directly calculated the complex parameter of the THz beam at the detector position using the ABCD matrices including the Si lenses to obtain the Gouy phase shift and to avoid the assumptions mentioned above.