Speaker: Prof Yukio Kawano

　  Time: Mar.20,2014 10:00AM

　　Venue:No. 101 Meeting Room, IOS, CAS 

The advantageous properties of terahertz (THz) waves, such as the important energy spectrum in the meV range, enable various applications of imaging and spectroscopy. However, since the THz region is located between the electronic and photonic bands, even basic components like detector and source have not been fully established, compared to the other frequency regions. The THz wave also has the problem of low imaging resolution, which results from a much longer wavelength than that of the visible light. By employing nanoelectronic devices based on a carbon nanotube (CNT), graphene, and a 2DEG in a semiconductor heterostructure, we have created a new type of THz sensing and imaging devices: 1) THz-photon sensor with a CNT/2DEG hybrid device: In order to achieve highly sensitive THz detection, we have studied THz response of a CNT/2DEG hybrid device. The utilization of the present device structure has enabled the detection of individual THz photons. 2) Near-field THz imager on one chip: The development of near-field THz imaging has been hindered by the lack of high transmission wave line and the low sensitivity of commonly used detectors. We present a new designed THz near-field imager, in which all the components: an aperture, a probe, and a detector are integrated on one semiconductor chip. The development of this device has made it possible to achieve nm resolution (~λ/540) even for the wavelength of 100-300mm. Electronic and molecular structures of semiconductors, plasmonic devices, and polymers have been visualized with this imaging device. 3) Wide-band, frequency-selective THz spectrometer with grapheme: We previously imaged THz emission distribution from GaAs-based 2DEGs. We have recently succeeded in observing THz photoconductivity of Dirac fermions in graphene, ranging over a wide frequency band of 0.8-33THz. This result demonstrates that the graphene device works as a wide-band, frequency-selective THz spectrometer. We have imaged potential fluctuations in the graphene device, suggesting the strong relation to the THz photoconductivity.

Yukio Kawano received the M. S. degree in basic science and engineering from University of Tokyo in 1998, and the Ph.D. degree in solid-state physics and engineering from the University of Tokyo in 2001. He worked as an assistant professor at the Department of Physics, University of Tokyo in 2001–2006 and as a Research Scientist at RIKEN during the period 2006–2011. He moved to the Tokyo Institute of Technology in 2011. His current position is associate professor at the Tokyo Tech. His research interests include THz technologies, scanning probe microscopy, and their applications to materials and devices research.