Discrete Fourier transform spectroscopy using precisely periodic pulse train of THz comb

 

Takeshi Yasui

Tokushima University, Japan

e-mail: yasui.takeshi@tokushima-u.ac.jp        http://femto.me.tokushima-u.ac.jp/eng/

 

 

Fourier transform spectroscopy (FTS) has been widely used in a variety of fields due to its high signal-to-noise ratio, simultaneous acquisition of a broad spectrum, and versatility for different radiation sources. Further improvement of the spectroscopic performance will widen its scope of applications. Here, we demonstrate improved spectral resolution by overcoming the time-window size limitation using a mode-locked terahertz (THz) pulse train as precisely periodic pulsed radiation in discrete Fourier transform spectroscopy (dFTS) [Optica, 2, 460 (2015)]. Since infinitesimal resolution can be achieved at harmonic components of its repetition frequency 1/T when the time-window size is exactly matched to the repetition period T, a combination of dFTS with a spectral interleaving technique achieves a spectral resolution limited only by the spectral interleaving interval. Linewidths narrower than 1/(50T) are fully resolved by THz-dFTS, allowing rotational-transition absorption lines of low-pressure molecular gases to be attributed within a 1.25 MHz band. Furthermore, I will present the application of this technique for the near-infrared region using the optical comb [Opt. Express, 23, 33184 (2015)].

 

 

Biography

Takeshi Yasui received his Ph.D. degree in mechanical engineering from the Tokushima University, Japan, in 1997, and Ph.D. degree in medical science from the Nara Medical University, Japan, in 2013.

   From 1997 to 1999, he worked as a Postdoctoral Research Fellow in the National Research Laboratory of Metrology, Japan. He was with the Graduate School of Engineering Science, Osaka University, Japan, from 1999 to 2010, and was briefly with the University of Bordeaux, France, in 2007, the University of Littoral Côte d'Opale, France, in 2010, and Osaka University, Japan, since 2010 as an Invited Professor. He is currently a Professor in the Graduate School of Science and Technology, the Tokushima University, Japan, and a Vice President in the same university. His research interests include THz instrumentation and metrology, nonlinear optical microscopy, and optical comb.

   Prof. Yasui received the Award for the Most Promising Young Scientist from the Optical Society of Japan in 1998, the Sakamoto Award from the Japan Society of Medical Electronics and Biological Engineering in 2006, the Optics Paper Award from the Japan Society of Applied Physics, and the Funai Award from the Japan Society of Mechanical Engineers in 2009.