Dr. Sri Ram Gopal Naraharisetty

Research Interests

• (1) Nonlinear Spectroscopy: Nonlinear Spectroscopy We utilize two independently tunable femtosecond laser pulses, covering the 350 nm to 10 µm spectral range. These pulses, generated using an optical parametric amplifier (OPA) and custom-built optical mixers, enable a wide range of experiments: (a) Two-beam pump-probe geometry. (b) Three-beam boxcar geometry for multidimensional spectroscopy. These setups allow us to explore ultrafast electronic and vibrational dynamics in complex materials
• (2) Pump-Probe Spectroscopy on 2D TMDC Materials: We have developed a home-built pump-probe setup specifically for studying 2D transition metal dichalcogenides (TMDCs). The pump energy is tuned above the bandgap or into the continuum (visible to UV), while probe pulses range from 1 to 10 µm via custom difference-frequency generation (DFG). A low-noise, fast-acquisition detection system enables the tracking of defect-mediated electronic recombination pathways. Both pump and probe beams offer flexible polarization control (linear, horizontal, left/right circular), allowing exploration of valleytronic decay dynamics.
• (3) Transient Absorption Spectroscopy for Solutions and Thin Films: We recently developed (2025) an in-house transient absorption spectrometer capable of pump-probe measurements with white-light continuum probing. Separate optical paths using silver and aluminum mirrors are designed for visible and UV pump pulses. A high-speed camera at the spectrometer image plane captures pulse-to-pulse spectra of both signal and reference beams, ensuring high temporal and spectral resolution.
• (4) Nonlinear Optical Characterization: We collaborate with multiple research groups to measure nonlinear optical properties such as third-order susceptibility using Z-scan and boxcar geometries. Our capabilities include custom setups for measuring photoluminescence, circular dichroism, and other optical responses in solutions, films, and photonic crystals, tailored to collaborative needs.
• (5) Laser Surface Patterning: Our laser-based surface structuring techniques enable fabrication of ultrablack surfaces with exceptional optical properties—achieving up to 99.2% hemispherical absorbance on stainless steel in the visible range. We also pattern metals and dielectrics to engineer wetting properties (from hydrophilic to superhydrophobic) and enhance applications such as thermoelectric generation, modern radiative heat sinks and solar energy harvesting
• (6) Laser-Induced Periodic Surface Structures (LIPSS) Fundamentals & Applications: We investigate the formation mechanisms and applications of LIPSS on a variety of materials, demonstrating control over their periodicity and morphology. By integrating plasmonic nanoparticles with these nano-patterned surfaces, we achieve extreme molecular sensitivity, potentially down to the single-molecule level—especially promising for biosensing applications. We also explore the fundamental physics behind LIPSS formation.