Welcome to my homepage!
I am Dr. Chinmay Khandekar. You will find here a compilation of my current and previous research works with collaborators, and other useful resources
related to optics and photonics. This research work focusses on fundamental understanding of light and using that to advance technology applications such as information displays, energy harvesting, light sources with highly specific requirements, imaging methods, sensors and detectors, thermal management solutions etcetera.
Feel free to leave a question or feedback. If you would like to work with me on interesting problems, check out opportunities and don't hesitate to contact. I will reply.
Solid-state thermal refrigeration technology based on light and nonlinear materials
Nonlinear Optics to beat the fundamental blackbody limit imposed by Kirchhoff's law
New Kirchhoff's laws
for nonreciprocal media
Thermal memory to store information as temperature
Pushing the frontier of Energy Harvesting
Passive nonlinear upconversion of infrared thermal radiation
Imagine being able to harness the untapped heat radiation from everyday objects around us, from your coffee cup to large-scale industrial waste heat. It sounds too good to be true, but what if we could fundamentally alter the thermal radiation from hot objects to make it usable? This is the question we set out to answer in this work. We explore the idea of upconverting long-wave infrared radiation to near-infrared wavelengths without using any external source of energy. The only physically viable approach to achieve this is through the nonlinear mixing of photons in the emitter itself. Thanks to advancements in nonlinear optics, we can now heat highly efficient nonlinear nanophotonic systems to make this a reality. However, the theoretical modeling of this mechanism is quite subtle as it requires consistency with known thermodynamic laws. We've developed a consistent theoretical framework to address this issue and have shown that we can indeed utilize the nonlinear upconversion mechanism to convert mid- and long-wave infrared photons to near-infrared photons which can then be harnessed using photovoltaic cells. This could potentially revolutionize the way we harness and utilize heat energy.
In short, we're working on a way to make heat energy usable by converting thermal radiation from everyday objects to a wavelength that can be harnessed with current technology. This could pave the way for new and innovative ways to generate electricity and reduce waste.
Advancing Augmented Reality Displays for a new era of Spatial Computing
Diffractive waveguide for augmented reality display
Are you ready for the future of human-computer interaction? With the augmented reality headset developed by Magic Leap, you'll be transported to a whole new world where digital 3D holograms seamlessly overlay the real world. At the heart of this technology is the diffractive optical waveguide, a glass waveguide with nanoscale patterns that guide light inside it. The projector launches light into the waveguide as totally internal reflected light rays, which travel inside the glass (in a manner similar to optical light confinement inside optical fibers) and get outcoupled upon encountering another diffraction grating. The outcoupled rays reach the eye and the user can see the digital content from the projector, while at the same time being able to see the real-world through the glass.
I currently work on designing these waveguides to provide the best-in-class augmented reality display experience. This technology is not just a simple upgrade, it's a leap forward in human-computer interaction, enabling spatial computing and opening the door to unique use cases across many industries such as healthcare, education, manufacturing, defense and engineering. With concurrent advances in AI, computer vision, and computing hardware, the augmented reality technology will change the way we interact with the world in the coming two decades, and the possibilities are endless.
Company website: MagicLeap
Designing a detector array for futuristic Direct Infrared Vision capability
Nanophotonic detector array to enable direct thermal infrared vision
Imagine being able to see the world in a whole new light, beyond the limitations of our natural vision. With specially engineered detector arrays, we can detect light outside the visible spectrum, allowing us to see the world in ways we never thought possible. One such example is thermal infrared (IR) cameras, which can detect mid- and long-wave infrared photons (typically in the range of 4 microns to 20 microns) generated thermally by objects. These cameras are now widely used for a variety of applications, such as electrical, mechanical, and structural inspection and maintenance, medical diagnosis, firefighting, and even defense.
What if this technology could be taken to the next level? Instead of being limited to handheld devices, IR cameras could be combined with head-mounted displays, allowing for a more immersive and hands-free experience. This is already being explored by some startups, and the possibilities are endless [video link].
In this work, we intend to take this concept even further by exploring the use of nanophotonic detector arrays in place of traditional microbolometer detectors. By using these arrays, we can directly provide an IR image without needing separate information displays. This not only simplifies the technology, but also makes it more lightweight and wearable, bringing us one step closer to a future where we can see the world in infrared in a technologically sleek manner.
Publications: OPEX2022 Editor's Pick
Discovery of New kinds of Circularly Polarized Light Sources
Thermally reconfigurable circularly polarized light source
Circularly polarized light has many applications, from medical imaging to high-speed data communication. In our recent work, we have made a breakthrough discovery that opens the door to a new way of producing circularly polarized light.
We stumbled upon the fact that thermal radiation from a system of two subwavelength antennas at unequal temperatures can be circularly polarized. This is a game-changer because it relies on thermal nonequilibrium or temperature gradients at the nanoscale, rather than the previously known concepts of using a chiral light source or a polarization conversion device. The mechanism has the potential to design reconfigurable circularly polarized light sources at mid-infrared wavelengths. By switching the temperature profile, the circular polarization of emitted light can be easily flipped. This means that we can harness the power of temperature gradients to create highly functional, reconfigurable light sources that have a wide range of applications.
Our discovery is a step forward in the field of nanophotonics and we are excited to continue exploring the full potential of this discovery and how it can be applied in various fields. See also follow-up work at PRAPPL2022
New approaches of Microscale and Nanoscale Heat Management using light
Nanoscale solid-state thermal refrigeration using nonlinear optics
Traditional thermoelectric coolers used for electronics heat-management can cool devices upto T~170K. To go below this temperature limit, the only other solid-state approach without using cryogenics and moving parts is that of laser cooling of solids containing rare earth ions. With that approach, temperatures as low as T~90K have been realized [See Melgaard et al]. To go further below this temperature, there is an incentive to think outside the box and conceptualize new solid-state refrigeration devices. Also, given the rapid miniaturization of all technologies, new refrigeration approaches can be quite useful in the near future for micro- and nanoscale heat management.
In this work, we propose a new method which uses resonantly enhanced nonlinear mixing of laser light with near-field thermal radiation. The most basic concept behind a thermal refrigeration is a reversed heat engine where work done by an external agent allows heat to flow from a cold body to a hot body. In our setup, the externally incident laser light drives a guided electromagnetic mode inside a slab with a nonlinear medium on top. The guided mode interacts evanescently with surface electromagnetic waves of an object placed within 100 to 300nm distance via a nonlinear frequency mixing mechanism. The work done or energy supplied by the incident laser light allows extraction of the thermal energy from the object thereby cooling it to lower temperatures. With this method, in principle, highly efficient thermal refrigeration can be performed using nanophotonic engineering and very low temperatures of T~10K can be realized starting from the device at ambient temperature.