Chandra Roychoudhuri

Honoring Leonard Mandel, Brian Thompson, Michael Hercher and James M. Burch

Submitted by Chandra Roychoudhuri

Tribute to Leonard Mandel, Brian Thompson, Michael Hercher and James M. Burch

I came to USA with a Fulbright Scholarship to understand the fundamental nature of light through experiments. Prof. L. Mandel of the Physics Dept. had accepted me. After a long discussion, Mandel transferred me to Prof. Brian J. Thompson with the instructions that I must learn diverse optical phenomena in depth to pursue my interests. I proposed to Brian that I would like to construct a compact pulsed Nd-glass laser with a large TEM00 mode. Prof. M. Hercher presented the design in a summer class. Brian suggested that I study the coherence properties of my home-built Nd-laser, which I started. Soon, Mandel donated his older pulsed Ruby laser (also home-built) to fix the cooling system and study its coherence properties. This was the laser that Mandel used to demonstrate his original single photon experiments.

I was employing the “local reference beam” holographic method with a Mach-Zehnder interferometer (MZ) to “freeze” the beam characteristics on the hologram and decipher the coherence information by analyzing the reconstructed wave front using CW He-Ne laser. Special films were made for this work by Kodak sensitive to 1µ. However, the vibrations due to the pulsed pump current to the lasers were reducing the hologram quality. The vibration was unavoidable as the pulsed laser was sitting inside one arm of the MZ. The visiting professor, Dr. J. M. Burch (the then Director of NPL, UK) solved the problem. I simply had to connect each of the four MZ mounts with four separate thin wooden sticks using bee’s wax to dampen the vibrations. The project was successful with a publication.

Then I needed a new project that had continuing funds to support me. Prof. Hercher came with the project to build a super stable multi-pass Fabry-Perot spectrometer to resolve directly the Brillouin spectra from solid crystals. He gave me an unusually innovative design and I built it successfully to record the resolved spectra. It is still preserved at the Institute. I got my PhD!

In 2014 I have published the book, “Causal Physics: Photon by Non-Interaction of Waves”, which was my goal when I came to USA. Mandel’s advice was critical to take the transfer to the Institute of Optics. I was able to diversify my deeper understanding of diverse optical phenomena because of systematic mentoring by Thompson, Hercher and Burch. I am very grateful to all these four great teachers.

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