S. Pancharatnam

Shivaramakrishnan Pancharatnam (1934-1969) was an Indian physicist who did significant work in the field of optics. He is most famous for his discovery of a type of geometric phase known as Pancharatnam phase for polarized beams passing through crystals. He was born in Tiruchirapalli in South India in 1934. He was elected a Fellow of the Indian Academy at the early age of 25. From 1964 until his death in 1969 at the age of 35 he was a Research Fellow of St. Catherine's College, Oxford, working in association with G. W. Series, F. R. S. His publications for this period were mainly concerned with the theory of effects found in experiments on optical pumping, e.g. double refraction in a gas due to spin alignment. Professor Series has written a brief but very valuable introduction on the life and work of Pancharatnam. He also prepared, for the Proceedings of the Royal Society, the last three papers from notes left by Pancharatnam.

Pancharatnam's work has generated interest amongst optical engineers who are looking for practical applications of his discoveries. This has already been incorporated in the the design of achromatic quarter and half-wave plates. Although another method has been used in the Zeiss version of the tuneable Lyot-Ohman filter, application for that due to Pancharatnam may still be found. He studied crystals for which the ellipsoid associated with the dichroism (or absorption index) does not have the same axial directions as the ellipsoid associated with the real part of the refractive index. Some of the peculiar effects which he discovered theoretically and demonstrated experimentally, may well have applications. Knowledge of others may warn the inventor of devices depending on birefringence that, in many crystals, certain devices will not work.

If Pancharatnam had lived longer he may have written a monograph on the optics of absorbing crystals. He was qualified to do so by his own contributions and by his erudition in regard to work done in the past 150 years and published in many languages.

Classic papers which brought out the concept of Anholonomy during parallel transport of Polarization states of light long before Michael Berry came up with the idea thereby making it apt to call it as Pancharatnam - Berry Phase.