Browsing by Author "Radhakrishnan, K."

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Investigation of third-order nonlinear optical properties of nanostructured Ni-doped CdS thin films under continuous wave laser illumination
(2019) Bairy, R.; Jayarama, A.; Shivakumar, G.K.; Radhakrishnan, K.; Bhat, U.K.
We report the third-order nonlinear optical (NLO) properties and optical limiting (OL) thresholds of pure CdS and Ni-doped CdS thin films have been investigated with the Z-scan technique under continuous wave laser excitation. Nanocrystalline CdS thin films with various doping concentrations of Ni (0%, 1%, 3%, 5% and 10 at.%) are prepared by spray-pyrolysis technique. XRD patterns reveal that all the prepared films are polycrystalline and the incorporation of Ni does not lead to major changes in the crystalline phase of Cd 1?x Ni x S thin films. The surface morphology of the prepared films is impacted by the Ni-doping and is indicated by Field Emission Scanning Electron Microscopy (FESEM) images. With an increase in Ni-doping concentration, the energy band-gap value decreased from 2.48 eV to 2.23 eV. From the Z-scan data, it is observed that the material show strong two-photon absorption (2PA) and with an increase in Ni-doping concentrations from 0 to 10 at.%, the nonlinear absorption coefficient (?) are enhanced from 0.92 10 ?5 to 4.46 10 ?5 (cm W ?1 ), nonlinear refractive index (n 2 ) from 0.2967 10 ?9 to 0.1297 10 ?8 (cm 2 W ?1 ) and thereby the third-order NLO susceptibility (? (3) ) values also increased from 1.7075 10 ?6 to 7.4743 10 ?6 (esu). OL characteristics of the prepared films are studied at the experimental wavelength. The results propose that the Cd 1?x Ni x S film is a capable material for nonlinear optical devices at 532 nm and optical power limiting applications. 2019, Springer Science+Business Media, LLC, part of Springer Nature.
Investigation of third-order nonlinear optical properties of nanostructured Ni-doped CdS thin films under continuous wave laser illumination
(Springer, 2019) Bairy, R.; Arasalike, A.; Shivakumar, G.K.; Radhakrishnan, K.; Bhat K, U.K.
We report the third-order nonlinear optical (NLO) properties and optical limiting (OL) thresholds of pure CdS and Ni-doped CdS thin films have been investigated with the Z-scan technique under continuous wave laser excitation. Nanocrystalline CdS thin films with various doping concentrations of Ni (0%, 1%, 3%, 5% and 10 at. %) are prepared by spray-pyrolysis technique. XRD patterns reveal that all the prepared films are polycrystalline and the incorporation of Ni does not lead to major changes in the crystalline phase of Cd1-xNixS thin films. The surface morphology of the prepared films is impacted by the Ni-doping and is indicated by Field Emission Scanning Electron Microscopy (FESEM) images. With an increase in Ni-doping concentration, the energy band-gap value decreased from 2.48 eV to 2.23 eV. From the Z-scan data, it is observed that the material show strong two-photon absorption (2PA) and with an increase in Ni-doping concentrations from 0 to 10 at. %, the nonlinear absorption coefficient (?) are enhanced from 0.92 x 10-5 to 4.46 x 10-5 (cm W-1), nonlinear refractive index (n2) from 0.2967 x 10-9 to 0.1297 x 10-8 (cm2 W-1) and thereby the third-order NLO susceptibility (?(3)) values also increased from 1.7075 x 10-6 to 7.4743 x 10-6 (esu). OL characteristics of the prepared films are studied at the experimental wavelength. The results propose that the Cd1-xNixS film is a capable material for nonlinear optical devices at 532 nm and optical power limiting applications. © Springer Science+Business Media, LLC, part of Springer Nature 2019.
Morphometric evidences for neotectonism in the Mulki River basin of coastal Karnataka, India
(2011) Radhakrishnan, K.; Lokesh, K.N.
Mulki River basin, a rectilinear midland river draining the coastal Dakshina Kannada districts of Karnataka located in the Mulki-Pulikat Lake axis in south Indian Peninsula shield has been analysed for various morphometric characteristics to understand the tectonic conditions of the basin along with supporting evidences of geomorphology, geology and structural features using Remote Sensing and GIS technology. The regional neotectonism suggested by earlier workers evidenced through geomorphologic features and geology of the area has been established through morphometric analysis. Even though Mulki, a 6 th order river basin obeys the Horton's laws of stream order it disobeys the Horton's law of stream length, indicating the regional uplift due to neotectonic activities. Fluctuating stream length ratio of successive stream orders in the basin again stress upliftment and a late youth stage development of geomorphic features reflected in slope and topographic conditions. The range of varying bifurcation ratios and the low Form Factor along with Circularity and Elongation Ratios strongly suggest a geologically and structurally controlled drainage system with elongated basin shape and high relief pointing towards neotectonism. A very low relief ratio of 0.008342, with entrenched meandering plain and a steep structural ridge within the basin indicates a rejuvenation of the basin with regional uplift. A very coarse graded drainage texture of 7.84 with low stream frequency of 2.5 and a drainage density of 1.877km/km 2 suggest that the area is having highly resistant permeable subsoil in a low relief terrain indicative of neogene tectonic activities. 2011 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.
Morphometric evidences for neotectonism in the Mulki River basin of coastal Karnataka, India
(2011) Radhakrishnan, K.; Lokesh, K.N.
Mulki River basin, a rectilinear midland river draining the coastal Dakshina Kannada districts of Karnataka located in the Mulki-Pulikat Lake axis in south Indian Peninsula shield has been analysed for various morphometric characteristics to understand the tectonic conditions of the basin along with supporting evidences of geomorphology, geology and structural features using Remote Sensing and GIS technology. The regional neotectonism suggested by earlier workers evidenced through geomorphologic features and geology of the area has been established through morphometric analysis. Even though Mulki, a 6 th order river basin obeys the Horton's laws of stream order it disobeys the Horton's law of stream length, indicating the regional uplift due to neotectonic activities. Fluctuating stream length ratio of successive stream orders in the basin again stress upliftment and a late youth stage development of geomorphic features reflected in slope and topographic conditions. The range of varying bifurcation ratios and the low Form Factor along with Circularity and Elongation Ratios strongly suggest a geologically and structurally controlled drainage system with elongated basin shape and high relief pointing towards neotectonism. A very low relief ratio of 0.008342, with entrenched meandering plain and a steep structural ridge within the basin indicates a rejuvenation of the basin with regional uplift. A very coarse graded drainage texture of 7.84 with low stream frequency of 2.5 and a drainage density of 1.877km/km 2 suggest that the area is having highly resistant permeable subsoil in a low relief terrain indicative of neogene tectonic activities. © 2011 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.