39 research outputs found
Investigations on Nonlinear and Radiative Properties of Certain Phatonic Materials
No full textLight in its physical and philosophical sense has captured the imagination of human
mind right from the dawn of civilization. The invention of lasers in the 60’s caused
a renaissance in the field of optics. This intense, monochromatic, highly directional
radiation created new frontiers in science and technology. The strong oscillating electric
field of laser radiation creates a. polarisation response that is nonlinear in character in
the medium through which it passes and the medium acts as a new source of optical
field with alternate properties. It was in this context, that the field of optoelectronics
which encompasses the generation, modulation, transmission etc. of optical radiation
has gained tremendous importance. Organic molecules and polymeric systems have
emerged as a class of promising materials of optoelectronics because they offer the
flexibility, both at the molecular and bulk levels, to optimize the nonlinearity and
other suitable properties for device applications. Organic nonlinear optical media,
which yield large third-order nonlinearities, have been widely studied to develop optical
devices like high speed switches, optical limiters etc.
Transparent polymeric materials have found one of their most promising applicationsin
lasers, in which they can be used as active elements with suitable laser dyes
doped in it. The solid-matrix dye lasers make possible combination of the advantages
of solid state lasers with the possibility of tuning the radiation over a broad spectral
range. The polymeric matrices impregnated with organic dyes have not yet widely
used because of the low resistance of the polymeric matrices to laser damage, their low
dye photostability, and low dye stability over longer time of operation and storage.
In this thesis we investigate the nonlinear and radiative properties of certain organic
materials and doped polymeric matrix and their possible role in device developmentCochin University of Science & TechnologyInternational School of Photonics, Cochin University of Science & Technolog
Investigations on Nonlinear and Radiative Properties of Certain Photonic Materials
No full textInternational School of Photonics,
Cochin University of Science & Technolog
Influence of particle size and dielectric environment on radiative lifetimes of colloidal cadmium selenide single photon emitters
No full textAbstract High repetition rate single-photon emitters are essential for all-optical quantum information processing, communications and metrology. The spontaneous emission lifetimes of colloidal cadmium selenide quantum dots are typically of the order of 10 ns, severely limiting their brightness and therefore their potential applications in quantum devices. Here we report on single-photon emission at room temperature with nanosecond lifetime from cadmium selenide quantum dots embedded in a polymer matrix. The study shows that the emission lifetime can be tuned by appropriately choosing the particle size and the dielectric constant of the surrounding medium. The quantum dots are synthesized using a green synthesis protocol and surface passivated using oleic acid. A Hanbury Brown and Twiss setup attached to an in-house constructed confocal microscope is used to efficiently couple and characterize the single-photon emission from an array of quantum dots. Detailed analysis of the second-order correlation function ( ) of single-photon emission from cadmium selenide quantum dots reveals the particle-size dependence of emission lifetimes. The study also shows that the quality of single-photon emission, as revealed by , reduces with increasing particle-size in the strongly confined regime
Tuning the nonlinear optical absorption in Au/BaTiO3 nanocomposites with gold nanoparticle concentration
No full textConfocal imaging of single BaTiO3 nanoparticles by two-photon photothermal microscopy
No full textAbstractWe report on the development of a nonlinear optical microscopic technique based on two-photon absorption induced photothermal effect capable of detecting individual nonfluorescent nanoparticles with high sensitivity. The method which is inherently confocal makes use of near infrared excitation at high repetition rates and would be of interest in deep tissue imaging. We demonstrate the applicability of the technique by imaging single BaTiO3 nanoparticles, a potential biomolecular label having high photostability, in a scattering environment at fast time scales with a pixel dwell time of 80 μs.</jats:p
Twin peak distribution of electron emission profile and impact ionization of ambient molecules during laser ablation of silver target
No full textLaser-induced plasma generated from a silver target under partial vacuum conditions using the
fundamental output of nanosecond duration from a pulsed Nd:yttrium aluminum garnet laser is
studied using a Langmuir probe. The time of flight measurements show a clear twin peak
distribution in the temporal profile of electron emission. The first peak has almost the same duration
as the laser pulse while the second lasts for several microseconds. The prompt electrons are
energetic enough ('60 eV) to ionize the ambient gas molecules or atoms. The use of prompt
electron pulses as sources for electron impact excitation is demonstrated by taking nitrogen, carbon
dioxide, and argon as ambient gases.Cochin University of Science & Technolog
Investigations on nanosecond laser produced plasma in air from the multi-component material YBa2Cu3O7
No full text
Twin peak distribution of electron emission profile and impact ionization of ambient molecules during laser ablation of silver target
No full textElectric field dependent photogenerated charge carrier separation in bipyridine containing poly(p-phenylene vinylene)
No full textThis article does not have an abstract
