Photoacoustic Effect in Condensed Matter — Historical Development

Abstract

The concept on which photoacoustic effects and spectroscopy are based was first reported in 1880 by Alexander Graham Bell¹. One of the transmitters of Bell’s so-called “photophone”, which he built together with Sumner Tainter, consisted of a mirror, which was activated by the sound waves of a voice, Fig. 1. A receiver section was made up of a hearing tube. It was mounted in that way that a hard rubber diaphragm was in the focus of a lens, Fig. 2. To explain the experimental observations Bell suggested that the illuminated front side of the diaphragm is heated and cooled periodically more than the rare side. The varying thermal expansion along the diaphragm leads to a periodically varying bending. This explanation was supported by calculations of Lord Rayleigh². The intensity of a beam of sunlight also was modulated by the mirror. Bell wrote to his father on the behave of this discover: “I have heard articulate speech produced by sunlight: I have heard a ray of the sun laugh and cough and sing! I have been able to hear a shadow, and I have even perceived by ear the passage of a cloud across the sun’s disk...