When you focus sunlight with a magnifying glass on a piece of paper, you burn the paper. Most of us have done this for fun when we were kids. While it is no doubt rather amazing to see paper burn by mere sunlight, those who are inclined to dive a bit deeper would ask ‘Why did the paper burn?!’

The answer is simple, yet can lead to great complexity. When you focus light by a lens, you confine it into a tiny spot - the smaller the focal length of the lens (meaning larger the magnification) - the larger is the light intensity (intensity being the power upon a unit area), so that a lot of power is incident on a very small area of paper. This causes the temperature of that region to become higher than that needed to burn paper. 

Similarly, if laser light - that can be focused into tinier spots than sunlight - can be focused into a liquid - say water, where tiny objects such as glass or plastic microspheres, metal nanoparticles or even bacteria or viruses are floating around - the focused light can actually ‘trap’ or confine the particles in its focal region. 

This is called Optical Tweezers.

Optical Tweezers have revolutionized the study of matter at the mesoscopic scale by their ability to trap such matter for very long periods of time in fluidic environments that are very well characterized. Such has been their effect on scientific research, that the Nobel Prize in Physics for 2018 was awarded to Prof. Arthur A Ashkin - the scientist who first discovered this novel technology way back in 1985 (see the paper here). While Ashkin was primarily awarded the Nobel for the knowledge that the technology has uncovered in Biology (see a nice review of Optical Tweezers in Biology here (put Perkins paper)), Optical Tweezers have opened new frontiers of research in every branch of science.

At the Light Matter lab in IISER Kolkata, we employ Optical Tweezers to study very diverse research areas - that range from studying the exotic properties of light itself to its effect on matter in a myriad ways which help uncover and understand the properties of microscopic matter, and thereby help facilitate new applications. Other than Optical Tweezers, we are also interested in biophotonics and frequency metrology, where in case of the latter - we are attempting to uncover new paradigms in hyperspectral imaging using Adaptive Optics, primarily towards space applications.

Broadly, our research areas may be categorized in the following areas: