1) Nano- and micro- scale thermal transport in solid structures by ultrafast optical pump-probe technique

 

This projects focuses on the control of nano- and micro- scale thermal transport degradation in swift heavy & slow light ion irradiated solids by ultrafast laser optical technique called picosecond time-domain thermorelfectance (TDTR) for nuclear and fusion energy applications. Phonon mediated thermal conduction in varios irradiated oxides, nitrides as well as novel thin films and superlattice-based thermal barrier coatings are researched. We are also conducting machine learning simulation to predict maximum thermal conductance across dissimilar interfaces.

 

2) Fast melting & ultrasonics in refractory metals by nanosecond pulse laser radiation

 

We are developing all-optical technique for automated high temperature control of thermophysical properties of refractory materials using nanosecond laser pulse-induced heating, melting and ablation and their detection by nanosecond time-resolved spectral radiometry and two-wave mixing photorefractive interferometric laser vibrometry. These techniques aim for laser pulse-based melting & real-time diagnostics of materials suitable for harsh conditions pertinent in nuclear & fusion energy and aerospace applications. We are also conducting molecular dynamics simulation of solid-to-melt phase transition in refractory metals under complex stress states.

 

3) Visco-elastic properties of complex fluids, nanoparticle colloids, biomaterials and GHz phononic crystals by Brillouin spectroscopy

 

We are investigating hypersonic viscoelastic properties of complex fluids, nanoparticle colloids, and biomaterials (protein solutions, mammalian bones, plant leaves, human body fluids) by Brillouin light scattering micro-spectroscopy using scanning 6-pass tandem Fabry-Perot interferometry coupled with confocal microscope imaging and single photon counting and VIPA spectrometer. This project pursues variety of optical sensing applications in biomedical, agricultural and petroleum sectors. Using this technique we also investigate phononic band-gap properties of oil-infiltrated periodically nanostructured polymeric phononic band-gap crystals periodically nanostructured by femtosecond laser-induced two-photon polymerization for potential application in the control of GHz acoustic waves and heat. We have also demonstrated surface plasmon-mediated enhancement of Brillouin scattering.

 

4) Raman micro-spectroscopy of Si-based nanostructures

 

We are investigating thermal transport and confined phonon modes and in various Si-based nano-engineered structures using confocal Raman micro-spectroscopy for thermal management,  photovoltaics and nanoelectronics applications.