Ever wondered how those temperature scanners that we see everyday from malls to hospitals, actually work? These devices employ infrared technology -- the long wavelength part of light, which we cannot see with bare eyes. Atoms are always moving and their speed determines the temperature of an object. These moving atoms emit radiation not as a visible light but as heat and for most everyday temperatures, these emitted wavelengths are quite long.
Infrared technology is everywhere. Infrared cameras are designed to record thermal gradients, where these cameras can be mounted on drones and used to monitor and security of the wildlife sanctuaries. Infrared imaging can be beneficial in medical science, just like ultrasound and X-ray imaging, where it can help in the diagnosis of abnormalities in the underlying tissues through variation of temperature of the skin. Further, polarization-resolved IR imaging can be even more valuable as it adds contrast between the objects and the ambient, which is crucial for medical science and security applications. During the recent CoVID-19 pandemic, infrared imaging has proven vital for detecting and containment of global pandemic outbreaks. Climate change is an extremely important global challenge and this year’s Nobel prize in Physics was awarded for the reliable prediction of global warming. In this context, infrared technology can help track changes in the climate by enabling monitoring of not only the temperatures of the ocean and landmass but also the composition of the atmosphere.
Despite all these cool applications, one of the major challenges in infrared technology is the miniaturization of the devices (such as waveplates, polarizers, and others) so that the size of the conventional platforms can be reduced up to a handheld device and even to chipscale. To address this, researchers at the Laboratory of Optics of Quantum Materials (LOQM), Indian Institute of Technology Bombay, with their collaborators at Massachusetts Institute of Technology (MIT), have successfully demonstrated an exotic property of extremely thin materials called hyperbolicity for making a robust ultrathin polarizer. Their findings are published in the journal Advanced Optical Materials, Wiley-VCH. The research article also has Mr. Anuj Kumar Singh from IIT Bombay and Professor Nicholas Fang and Dr. Sang Hoon Nam from MIT as coathors.
“Light waves have electric fields oscillating in different directions. Hyperbolicity in our grown crystals makes them behave like a shiny metal for electric field oscillating in one direction and like an insulator such as glass for the perpendicular direction”, explains Dr. Saurabh Dixit, an equally contributing lead author of the work. This property of hyperbolicity arises from the peculiar direction in which the atoms of this exotic material molybdenum oxide vibrate. The researchers demonstrated that if we choose the geometry intelligently, one can exploit these vibrations to make ultrathin infrared optical components which are not only high performance at room temperature but also show robustness at higher temperatures! “This is a very important result because when these devices are deployed on the field, one cannot maintain laboratory-like temperature conditions”, remarks Nihar Ranjan Sahoo, equally contributing lead author of the work.
Such materials have importance in designing low-cost, miniaturized, and flat IR optical components and devices. “In this wavelength range, typical components are made by making nanoscale or micron scale patterns, where complex and expensive lithography techniques are required. In this work, we demonstrate that these exotic crystals grown in our lab can provide these functionalities as it is without the associated fabrication complexity. This is the first time we show that these infrared devices can withstand high temperatures. Our current focus is on chip-scale integration and achieving even larger operational bandwidth than the current demonstration”, says Professor Anshuman Kumar, lead principal investigator of the research project, commenting on the technological significance and future directions of this research.
Article written by
Dr. Saurabh Dixit and Nihar Ranjan Sahoo
Author(s) of the research/ study
Nihar Ranjan Sahoo*, Saurabh Dixit*, Anuj Singh, Sang-Hoon Nam, Nicholas X. Fang, Anshuman Kumar
* equal author contribution
Image/ Graphics credit