obituary In memory of Narinder Singh Kapany The Indian scientist and passionate entrepreneur responsible for pioneering work on optical fbres and biomedical optics has passed away aged 94.

arinder Singh Kapany is considered While less well known, Kapany’s by many as the unsung hero and contributions to push the frontiers of Nfather of fibre optics, with his diverse biology and biomedical optics were also pioneering achievements in the area arguably crucial. Following the invention of the laser not receiving the level of recognition that in 1960, he promptly systematically studied they truly deserve. Kapany was one of the interaction between green and infrared the first physicists to demonstrate that a laser pulses and the eye’s retina, resulting in bundle of fine glass fibres could transmit the ability to laser weld a detached retina to high-resolution images, and performed the eye’s choroid in the early 1960s to cure many early experiments to investigate the retinal blindness5. He was also one of the physics of coupling and propagation of light first scientists to design a fibre-optics-based in fibres1–3. In biomedical optics, he designed scheme for optical oximetry of blood6, fibre-optic hypodermic probes for imaging which measures the level of oxygen of living human tissue4, conducted early saturation in blood via its optical absorption experiments to cure retinal detachment characteristics. Optical pulse oximetry with lasers5 and also demonstrated optical has since evolved to become a routine and oximetry of blood6. He also designed important optical technique today. key components for fibre-optics-based Still fascinated by the potential for 7 communication systems and made A line sketch of N. S. Kapany. image transmission through optical fibres, pioneering contributions in solar energy. Kapany later used pulsed light sources to Kapany died in Redwood City, California, transfer a three-dimensional image11,12 and USA, on 4 December 2020, aged 94. in both academia and industry. He first performed extensive analysis of point-spread Today, optical fibres are indispensable spent time on the east coast at the University functions and image assessment parameters to a wide variety of fields. They form the of Rochester and the Illinois Institute of in optical systems3. These early works paved backbone of optical data transmission Technology before in 1960 moving to the way to modern engineering tools for systems that carry the Internet around California to found several business ventures laser ranging, laser-scanning and distance the world, and generate and guide intense and conduct research at the University of measuring tools. laser light for tasks in material processing, California at Santa Cruz. Kapany also had interest in harnessing biomedicine diagnostics and laser Ever since his schooldays, Kapany had solar energy for practical applications. He surgery8. Fibres also play a critical role in been curious about the idea of bending the improved design of efficient solar panels that spectroscopy and optical sensing of chemical propagation of light and using it for imaging can be mounted on walls or windows, and and biological substances. The genesis of the and medical applications. His interests obtained several patents for apparatus for field of fibre optics owes much to Kapany, resonated well with his PhD supervisor solar window and solar walls for cooling an who was not only responsible for many in London, Harold Hopkins, who advised environment13. scientific papers and patents in the area but him to experiment with a bundle of glass After early experiments around 1960, also authored the first comprehensive book cylinders. Kapany worked tirelessly to the experimental work on fibre optics had on the topic (Fiber Optics: Principles and assemble a coherent bundle of hundreds virtually stopped; both Hopkin and van Applications) in 1967. of glass fibres with a diameter of a few tens Heels abandoned the field but Kapany Kapany was born in Moga, Punjab, of micrometres and used them to build a remained steadfast. He continued with his India, on 31 October 1926 and his early flexible fibrescope for transmitting images passion of image transmission, biomedical schooling took place in Dehradun, a that was described in a paper published instrumentation and sensors using fibre beautiful city in the foothills of the with Hopkins in Nature on 2 January 19541. optics throughout his career. Himalayas. His career first started with The work was simultaneously published After highly transparent fibres were employment in a local ordinance factory alongside a paper by Abraham Cornelius fabricated in the 1960s by Charles Kao14, where he designed and fabricated optical Sebastiaan van Heel from Delft, the who received the 2009 Nobel Prize in instruments before moving to London in Netherlands, describing similar research on Physics for his achievements, Kapany was the early 1950s for his higher studies. He fibre-based light transmission9, and the two instrumental in making technological undertook a PhD at Imperial college in papers inspired the development of modern innovations such as fibre couplers, (de-) London, UK, during which he experimented fibre endoscopes. multiplexers and amplifiers to push forward with micrometre-diameter optical fibres Kapany went on to devise ingenious optical fibre optical communication system7. for image transmission and fabricated a ways to characterize quality of optical He had about 100 patents and a similar flexible fibrescope1 — a precursor to modern fibre during the fabrication using optical number of publications. endoscopes. interferometry10. He also designed apparatus Kapany was a passionate entrepreneur After receiving his PhD in 1955 he to fabricate a glass fibre with a cladding, who launched several companies relocated to the United States, where he a technique still used to produce modern related to optical technologies as well stayed for the remainder of his life, working fibres commercially. as the commercialization of optical

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instrumentation, notably Optics Technology extraordinary. He remained indefatigably References in 1960, Kaptron in 1973 and K2 Optronics enthusiastic about science, innovation and 1. Hopkins, H. & Kapany, N. S. Nature 173, 39–41 (1954). 2. Kapany, N. S. Nature 184, 881–883 (1959). in 2000. entrepreneurship, and continued working 3. Kapany, N. S. Nature 188, 1083–1086 (1960). When asked about why he named his into his late 80s. His curiosity of bending 4. Capellaro, D., Kapany, N. S. & Long, C. Nature 191, 927–928 company K2 Optronics after the second light changed the course of history. ❐ (1961). 5. Kapany, N. S., Peppers, N. A., Zweng, H. C. & Flocks, M. Nature highest mountain in the world, “one 199, 146–149 (1963). must be modest” was his reply. He also Kamal P. Singh ✉ 6. Kapany, N. S. & Silbertrust, N. Nature 204, 138–142 (1964). made donations to support the creation Department of Physical Sciences, Indian Institute of 7. Kapany N. S. & Unterleitner, F. C. US patent 4,479,697 (1984). 8. Fermann, M. & Hartl, I. Nat. Photon 7, 868–874 (2013). of scientific chairs at institutions and Science Education and Research Mohali, Manauli, 9. van Heel, A. C. S. Nature 173, 39 (1954). contributed generously for spreading Indian Punjab, India. 10. Reifel, L. & Kapany, N. S. Rev. Sci. Instrum. 31, 1136 (1960). culture through his unique collection of ✉e-mail: [email protected] 11. Kapany, N. S. Proc. SPIE https://doi.org/10.1117/12.953588 (1973). 12. Kapany, N. S. US patent 3,682,553 (1972). paintings and arts. 13. Kapany, N. S. & Hintzke, M. A. US patent application 13/050,887 The passion, creativity and practical Published online: 21 April 2021 (2012). instrumentation skills of Kapany were https://doi.org/10.1038/s41566-021-00812-z 14. Kao, K. C. & Hockham, G. A. Proc. IEE 113, 1151–1158 (1966).

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