Exploring frontiers between optics and electronics—1950 to the present: A prominent period

Progress in far-infrared (FIR) and terahertz (THz) techniques are described. There are three ways of approach to this frontier region; optic, electronic and quantum electronic approach. This paper describes optic, i.e., grating and Fourier transform spectroscopy, and quantum electronic, i.e. far-infrared lasers and terahertz time-domain spectroscopy/imaging (THz-TDS). Applications by use of each method are shown.