Integrated optics

The appearance of “Integrated Optics: An Introduction” by Stewart E. Miller in the September 1969 Bell System Technical Journal signalled the birth of an activity that now occupies thousands of researchers. Bell Labs, among others, had been concerned with optical communications for some time, encouraged in this activity by the advent of the laser. Miller pointed out that the then typical optical telephone repeater, involving a laser, modulator, detector, lenses, and so on, spread out on an optical bench, was a form of extremely short‐range radio communication and as such suffered from a number of difficulties. The apparatus was sensitive to ambient temperature gradients, to temperature changes, to mechanical vibrations of the separately mounted parts. The elegant solution to these problems proposed by Miller was to combine the separate components on the same substrate or chip, connecting them by miniature transmission lines or waveguides. Because the size of the components need only be of the order of the wavelength of light in one, and possibly two, dimensions, the substrate could be quite small—centimeters or less. He proposed calling such an assembly of components an “integrated optical circuit,” in view of its analogy to the assembly of electrical components on an integrated circuit chip.