Eminent physicist P. Hariharan died on Sunday in Berkeley, California. He was 89.

Dr. Hariharan was the son of Prof. H. Parameswaran (H. P. Waran) of Presidency College and the son-in-law of Alladi Krishnaswamy Iyer. He was born on December 24, 1926.

He worked at the National Physical Laboratory (NPL), New Delhi from 1949 to 1951 and then at the National Research Council, Ottawa from 1951- 1954. On returning to NPL, Dr. Hariharan received a PhD for his work on photographic resolving power. Subsequently, he held key posts at several scientific institutes and organisations and was also an honorary visiting professor at the University of Sydney.

Dr. Hariharan's research contributions include the design of a new three-beam interferometer, the double-passed Fabry-Perot interferometer, and the first practical radial-shear interferometer. He was also the first to apply digital phase-shifting techniques to holographic interferometry for measurements of vector displacements and strains. Dr. Hariharan has published more than 200 papers and has authored four books. Dr. Hariharan was a recipient of several awards, including the Joseph Fraunhofer Medal of the Optical Society of America, the Thomas Young Medal of the Institute of Physics, London and the Walter Boas Medal of the Australian Institute of Physics.

Dr. Hariharan is survived by two children, Dr. Iswar Hariharan and Dr. Lakshmi Hariharan, with whom he was living in the United States.