Abstract
The generation, detection, and applications of terahertz waves (electromagnetic waves whose frequency
ranges from about 0.1 THz ~ 10 THz) have been attracting great interest for about 20 years.
Unfortunately, the generation and detection of terahertz waves are complicated because this band is located
on the border between electronics and photonics. However, recent advancements, particularly in
devices that emit continuous or quasi-continuous terahertz waves and in unique applications of time domain
spectroscopy are opening up real-world applications. In this preface, we briefly summarize the related
history and give an overview of this special issue.
