Photoelectric Mixing As a Spectroscopic Tool

Photoelectric mixing is at present an effect which can be displayed with great difficulty. When combined with optical masers (or lasers), it may provide the basis of relatively simple optical measurements using radio-frequency-like receivers. In these receivers the detector or mixer is a photocell or other photoelectric device. Two general receiver types are considered and termed, following rf terminology, low-level and superheterodyne receivers. The low-level receiver offers the possibility of simple observations of the special shape of the laser output. The superheterodyne receiver offers the possibility of measurement of the shapes of ordinary spectral lines although good resolution will require long observation times. As an instrument for comparing two laser outputs the superheterodyne optical receiver is capable of such extraordinary sensitivity that two lasers may be compared out to physical separations of 106 km.