Conference Papers
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Item Active contours technique for fringe evaluation of complicated fringe patterns(2010) Joishi, R.; Reddy, K.P.J.; Hegde, G.M.An improved technique based on active contours approach is presented for the analysis of non-uniform finite fringe interferograms. The technique is validated by demonstrating its application in analyzing the interferomertic image having non-uniform fringe pattern generated by a supersonic flow in front of a blunt body. A filtering method for identifying the flow parameters is presented as an extension of this technique. Proposed technique also provides an estimate of the heterodyning spatial frequency. © 2010 SPIE.Item Quantitative density imaging of subsonic jet using planar laser induced fluorescence of MEK(2012) Shelar, M.S.; Umesh, G.; Hegde, G.M.; Jagadeesh, G.; Reddy, K.P.J.Quantitative molecular density distribution of Methyl ethyl ketone (MEK) in turbulent nitrogen jet (Re≈2-3×103) was measured using PLIF technique. The tracer (MEK) was seeded in the nitrogen jet by purging through the liquid MEK at ambient temperature. Planar laser sheet from frequency quadrupled, Q-switched, Nd: YAG laser (266 nm) was used as an excitation source. Emitted fluorescence images of jet flow field were recorded on CMOS camera. To obtain quantitative density profile, the dependence of PLIF intensity on MEK partial pressure was employed. Thus an instantaneous quantitative density image of nitrogen jet, seeded with MEK was obtained. © 2012 IEEE.Item Electronic band structure and photoemission spectra of graphene on silicon substrate(SPIE spie@spie.org, 2014) Javvaji, B.; Ravikumar, A.; Shenoy, B.M.; Roy Mahapatra, D.; Rahman, M.R.; Hegde, G.M.Synergizing graphene on silicon based nanostructures is pivotal in advancing nano-electronic device technology. A combination of molecular dynamics and density functional theory has been used to predict the electronic energy band structure and photo-emission spectrum for graphene-Si system with silicon as a substrate for graphene. The equilibrium geometry of the system after energy minimization is obtained from molecular dynamics simulations. For the stable geometry obtained, density functional theory calculations are employed to determine the energy band structure and dielectric constant of the system. Further the work function of the system which is a direct consequence of photoemission spectrum is calculated from the energy band structure using random phase approximations. © 2014 SPIE.Item Optoelectronic properties of graphene silicon nano-texture(Institute of Electrical and Electronics Engineers Inc., 2014) Brahmanandam, J.; Ajmalghan, M.; Abhilash, R.K.; Roy Mahapatra, D.; Rahman, M.R.; Hegde, G.M.Graphene on silicon with silicon dioxide quantum dots is a promising opto-electronic material. The optical band gap and the corresponding optical conductivity are estimated using the density functional approach with the combination of molecular dynamics. The regular repeating unit cell of graphene silicon nano-texture is identified using the classical molecular dynamics simulations. Electronic calculations predict the optical band gap is around 0.2 eV and the optical conductivity is identified to be 0.3 times the quantum conductance. © 2014 IEEE.Item Optoelectronic properties of graphene on silicon substrate: Effect of defects in graphene(SPIE spie@spie.org, 2015) Javvaji, B.; Ajmalghan, M.; Roy Mahapatra, D.; Rahman, M.R.; Hegde, G.M.Engineering of electronic energy band structure in graphene based nanostructures has several potential applications. Substrate induced bandgap opening in graphene results several optoelectronic properties due to the inter-band transitions. Various defects like structures, including Stone-Walls and higher-order defects are observed when a graphene sheet is exfoliated from graphite and in many other growth conditions. Existence of defect in graphene based nanostructures may cause changes in optoelectronic properties. Defect engineered graphene on silicon system are considered in this paper to study the tunability of optoelectronic properties. Graphene on silicon atomic system is equilibrated using molecular dynamics simulation scheme. Based on this study, we confirm the existence of a stable super-lattice. Density functional calculations are employed to determine the energy band structure for the super-lattice. Increase in the optical energy bandgap is observed with increasing of order of the complexity in the defect structure. Optical conductivity is computed as a function of incident electromagnetic energy which is also increasing with increase in the defect order. Tunability in optoelectronic properties will be useful in understanding graphene based design of photodetectors, photodiodes and tunnelling transistors. © 2015 SPIE.Item Photonic crystal ring resonator: A promising device for a multitude applications(SPIE spie@spie.org, 2017) Yadunath, T.R.; Kumar, R.R.; Tupakula, T.; Kandoth, A.; John, K.; Ramakrishnan, R.K.; Das, P.P.; Badrinarayana, T.; Mohan, S.; Hegde, G.M.; Srinivas, T.In this paper a 2D Photonic Crystal array in SOI platform having hexagonal periodicity with a ring defect incorporated along with two bus waveguides is conceptualized and realized for various applications of optical communication, sensing etc. The ring structure filters out a resonant wavelength from the spectrum carried to it through the line defect where the resonated peak is determined by the effective ring radius. The hexagonal architecture enables more coupling length than an ideal ring structure which helps in better intensity accumulation. The resonant peak exhibited at 1554nm in simulation, which is observed in the optical characterization at 1543nm. This is attributed to the fabrication tolerance. © 2017 SPIE.