Subject2D materials based metasurfaces & THz near-field spectroscopy
Date2020.02.11 (Tue) 14:00
SpeakerTeunteun Kim (Institute for Basic Science)
Manipulation of light is of paramount importance in optics. Recently, progress has been made over a class of new artificial media, metamaterials, which consist of the arrangement of periodic subwavelength optical elements that exhibit unusual optical properties beyond what natural materials can offer. Since their effective electromagnetic properties can be engineered by designing subwavelength scale metallic structures, called ‘meta-atoms’, these artificially constructed materials have promised a vast variety of otherwise unexpected physical phenomena such as a negative index of refraction, gigantic chirality, and invisible cloak. Even though fascinating effects can be obtained by passive metamaterials described above, for practical applications, it is highly desirable to enable dynamic tunability to their operations.
In this talk, I will introduce electrically controllable unique optical properties such as optical activity , anomalous refraction and focusing , and analogue of electromagnetically induced transparency (EIT)  by integrating 2D graphene layer onto metamaterials with different functional unit cells. The switching and linear modulation of unique optical properties are realized by changing coupling among meta-atoms or electrical conductivity of metallic structures caused by increased sheet conductivity of the single layer graphene. Besides, I will introduce a single annular aperture as a practical platform for THz absorption spectroscopy. THz tip-probe near-field measurement system is used to investigate the electric field distribution in a single annular aperture and near-field image clearly shows that the electric field is strongly confined at the gap. After inserting lactose in the gap, we can couple the intense optical fields of the single annular gap into the vibrational modes of lactose molecules. We observed high contrast THz absorbance signals drastically suppressing of the transmitted light. This result indicates that the single annular aperture can be used as a platform that is promising avenues toward future drastic miniaturization of THz devices and sensors.