How it began
Jagadis Chandra Bose, born in India in 1858, studied at Cambridge, where Lord Rayleigh was one of his lecturers, and returned to India as officiating professor of physics at Presidency College in Calcutta. In 1894 he began experiments there on the refraction, diffraction and polarization of electromagnetic waves at wavelengths from 2.5 cm down to 5 mm. In 1895 he gave his first public demonstration of electromagnetic waves in Calcutta. In January 1897, invited by Lord Rayleigh, he reported on the experiments at the Royal Institution in London.
How it works
Bose built a complete set of millimeter-wave components. The IEEE milestone record lists a spark transmitter, a coherer, a dielectric lens, a polarizer and a horn antenna. He used round, square and rectangular waveguides and a pyramidal horn antenna, which he was the first to use. Lenses were designed from the refractive index he measured at the working wavelength. Polarizers included twisted jute and a book with sheets of tinfoil between its pages. To receive the waves he used point-contact junctions connected to a sensitive galvanometer, including detectors made of galena crystal.
What changed first
In 1896 the Daily Chronicle of England reported that Bose had transmitted signals to a distance of nearly a mile. David Emerson of the National Radio Astronomy Observatory notes that Bose's public demonstration of 1895 came before Marconi's signaling experiment on Salisbury Plain in May 1897. Bose published his results in the Proceedings of the Royal Society in 1897. Patent rights for the use of galena crystals to detect electromagnetic radiation were granted to him in 1904.
What lasted
Emerson writes that many microwave components familiar today, including waveguide and horn antennas, were in use in Bose's laboratory, and that further work at millimeter wavelengths was almost nonexistent for nearly 50 years afterward. A later review of semiconductor history gave Bose priority for the use of a semiconducting crystal as a detector of radio waves. The IEEE has recognized the work as a Milestone titled First Millimeter-wave Communication Experiments by J. C. Bose, 1894-96.
Where it stands today
Some of Bose's original equipment still exists at the Bose Institute in Calcutta, where Emerson examined and photographed it in 1985. Emerson also reports that a receiver operating at a wavelength of 1.3 mm on the 12 Meter Telescope of the National Radio Astronomy Observatory drew on a concept from Bose's apparatus. Bose was elected a Fellow of the Royal Society in 1920.
