This is Photonics.

The endeavour of measurement is integral to the construction of knowledge in the natural sciences. The finer and more reliable our measuring ruler is, the more confident we can be about the evidence we present and the worldview we construct. Light provides us with such a precise ruler.

It is an established fact that the speed of light in vacuum, often written as \(c\), is a universal constant, while its colour defined by its optical frequency, is intrinsic to the very atomic structure of the source that produces it. With these two quantities pinned down, we can with a very high degree of confidence use light as a ruler, measuring lengths all the way from microscopic scales (\(\sim10^{-9} m \)) to the astronomical (\(\sim10^{5} m \)).

But light can be more than just a ruler.

Photonics is usually defined as the study of the science of light and its applications. But its epithet of being a key enabling technology is more appropriate, given the widespread social and economic impact it generates. Our understanding of light, how it interacts with matter gave us lasers, and the world never has remained the same since. The world has been made simultaneously smaller and larger by the Internet, which owes its existence to the transoceanic high-speed fibre-optic network. The ruler-like capabilities of light have spawned the multi-billion-dollar industry of optical sensors, offering devices that can measure surface roughness, millimolar gas concentrations and gyroscopes. Lasers have given us optical tweezers, with the ability to literally unzip DNA. We now have microscopes that reveal the structure of biological features with unprecedented details, and even see their dynamics down to the single-molecule level. And then there is the sub-discipline of nanophotonics and metamaterials spawning devices with the potential to completely transform our technological ecosystem.

Photonics is a gateway discipline.

Photonics has the the ability to offer incredible insights in seemingly disconnected disciplines. The tests of Einstein’s General Theory of Relativity are particularly exemplary, starting from Sir Arthur Eddington’s detection of deflected starlight by the Sun back in 1919, all the way to the more recent Nobel prize winning confirmation of gravitational waves. Another interesting example is in the study of turbulence, a long-standing prize problem in physics, which is finding an unusual ally in the field of nonlinear fibre optics. The beauty of it is, a scientist or engineer can utilize the fundamental principles of photonics and the tools offered by it in their own areas of work, or even enter a field distinctly different from their own, yet arrive at a fresh perspective of the underlying mechanics they set out to investigate. Photonics thus offers a way to bridge the gap between seemingly disjoint domains, facilitating fruitful interdisciplinary research in the process.

Our unending quest for understanding the very nature of light has yielded (and continues to yield) remarkable insights, leading to fantastic discoveries that expand our knowledge of the universe we live in. In its most rudimentary form, photonics may just conjure a ruler. But in its most potent avatar, it stands to deliver unprecedented insight, with the potential to enable significant leapfrogging advances.

May 16th is the International Day of Light. Learn more at https://www.lightday.org/

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This is Photonics. by Srikanth Sugavanam is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.