Charge transfer and Ultrafast Nonlinear Optical Spectroscopy of 2D Materials
Dr. Sudhakara Reddy Bongu | Indian Institute of Technology, Madras Chennai, Indiatalks about
In my doctoral degree my research activities focused on “charge transfer, energy transfer and nonlinear optical phenomena in 2D material graphene –metal nanoparticles and graphene – dye systems”. We studied the graphene-silver nanoparticles hybrid system under excitation of fs laser at near LSPR band of silver nanoparticles (400 nm) and away from it (800 nm). The results show the large enhancement in saturable absorption response and optical power limiting of graphene upon decorating with silver nanoparticles under resonant excitation of LSPRs band. Efficient switchable nonlinear optical response has been observed in the gold nano particle-graphene system under 532 nm excitation. The interaction of dye-graphene system shows the diverse charge transfer effect depends on dye charge and solvent. Efficient ground state charge transfer complex observed with cationic dye which found to exhibits the enhanced optical power limiting response than the pristine graphene. First time we have developed the fs white light Z-scan setup in our laboratory with the help of photonic crystal fiber on pumping with 772 nm of Ti: Sapphire oscillator. We have demonstrated the nonlinear optical response of a standard dye IR26 over 480 nm to 850 nm wavelength ranges by measuring a single white light Z-scan measurement. In my post Ph.D, I have worked on ultrafast nonlinear optical spectroscopy and magneto-optical effect in emerging 2D layered materials. We greatly focused on the various exotic nonlinear optical properties including nonlinear absorption, second harmonic emission, charge transfer study, transient absorption spectroscopy on novel 2D materials and their hetero structures for desired and high efficient photonic application. Initially, we have focused on a review article which briefly covers the key developments pertaining to research in the nonlinear optics of 2D layered materials. The study on platinum chalcogenides hetero structures found the enhanced nonlinear absorption and ultrafast carrier recovery dynamics which can be utilized in for high efficient saturbale absorber in pulsed lasers. By the systemic study of photo-physical properties and by femtosecond transient absorption spectroscopy I have detects the mechanism for efficient quenching process between ultrathin 2D bismuthene sheets and dye molecules which is utilized for the ultrasensitive detection of MicroRNA. I have implemented the home made reflective Z-scan setup for specifically characterizing the reflective type nonlinear optical photonic materials of germanene which found in high efficient saturable absorber than the bench mark 2Dmaterial graphene. The experimental setup is quite complicated and desirable for the 2D materials samples which are coated on the opaque substrate. Currently I have been working on various projects of nonlinear optical and ultrafast spectroscopy and magneto-optical effect in ultra thin 2D layered materials.