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

 

This project focuses on study and control of nano- and micro- scale thermal transport degradation in nanostructured and swift heavy 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 metal oxides, nitrides, alikali halides as well as novel nanostructured thin films are researched. We are also conducting machine learning simulation to predict maximum thermal conductance across dissimilar interfaces.

 

2) Raman and photoluminecense micro-spectroscopy of nanostructured and irradiated materials

We are investigating thermal transport and confined phonon modes in various Si-based nano-engineered structures using confocal Raman opto-thermal micro-spectroscopy for thermal management,  photovoltaics and nanoelectronics applications. We are also exploring surface plasmon enhanced Raman scattering effects using Si nanowire structures and phonon-assisted anti-Stokes PL in nanostructured perovskites, as well as color center radiation defects quantification and qualification by PL and potical absorption spectroscopies. 

 

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

We are investigating hypersonic viscoelastic properties of irradiated functional polymers, complex fluids, nanoparticle colloids, and biomaterials (protein solutions, mammalian bones and animal meat muscles, plant leaves, human body fluids) by Brillouin light scattering micro-spectroscopy using scanning 6-pass tandem Fabry-Perot interferometry coupled with confocal microscope 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) 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 to nuclear & fusion energy and aerospace applications. We are also conducting molecular dynamics simulation of solid-to-melt phase transitions in refractory metals under complex stress states.