Some relations between microwaves and optics

Summary form only given. The many quasi-optical techniques used with microwaves are now well-known, but the development of these provides a number of interesting case histories. In addition to the ties based upon field theory, there were important interchanges in circuit concepts, Schelkunoff demonstrated the importance of impedance concepts in wave problems, the scattering matrix approach found use with lumped-element circuits, and filter concepts were interchanged between the two fields. More recently, systems concepts based upon chirp radar and spread-spectrum techniques have played a role in the development of the ultrashort optical pulses. These pulses in turn have been used in the study of materials in the millimeter-wave region.<>