Sreeja., S; Dr. P Radhakrishnan(Cochin University of Science and Technology, June 7, 2014)
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Abstract:
Important issues related to femtosecond (fs) pulses and its
relevance to this thesis are discussed. A fundamental characteristic, like the timebandwidth
product for fs pulses is decribed in detail. A brief review of generation of
ultrashort pulses and its propagation through an optically transparent media are
presented. Interaction of strong pulses with matter and different ionization processes are
also described. An overview of the thesis is presented at the end
Rejeena, I; Dr. P. Radhakrishnan(Cochin University of Science and Technology, April 23, 2015)
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Abstract:
Nonlinear optics is a broad field of research and technology that
encompasses subject matter in the field of Physics, Chemistry, and Engineering.
It is the branch of Optics that describes the behavior of light in nonlinear media,
that is, media in which the dielectric polarization P responds nonlinearly to the
electric field E of the light. This nonlinearity is typically only observed at very
high light intensities. This area has applications in all optical and electro optical
devices used for communication, optical storage and optical computing. Many
nonlinear optical effects have proved to be versatile probes for understanding
basic and applied problems. Nonlinear optical devices use nonlinear dependence
of refractive index or absorption coefficient on the applied field. These nonlinear
optical devices are passive devices and are referred to as intelligent or smart
materials owing to the fact that the sensing, processing and activating functions
required for optical processes are inherent to them which are otherwise separate
in dynamic devices.The large interest in nonlinear optical crystalline materials has been
motivated by their potential use in the fabrication of all-optical photonic devices.
Transparent crystalline materials can exhibit different kinds of
optical nonlinearities which are associated with a nonlinear polarization. The
choice of the most suitable crystal material for a given application is often far
from trivial; it should involve the consideration of many aspects. A high
nonlinearity for frequency conversion of ultra-short pulses does not help if the
interaction length is strongly limited by a large group velocity mismatch and the
low damage threshold limits the applicable optical intensities. Also, it can be
highly desirable to use a crystal material which can be critically phasematched
at room temperature. Among the different types of nonlinear crystals, metal halides and
tartrates have attracted due to their importance in photonics. Metal halides like
lead halides have drawn attention because they exhibit interesting features from
the stand point of the electron-lattice interaction .These materials are important
for their luminescent properties. Tartrate single crystals show many interesting
physical properties such as ferroelectric, piezoelectric, dielectric and optical
characteristics. They are used for nonlinear optical devices based on their optical
transmission characteristics. Among the several tartrate compounds, Strontium
tartrate, Calcium tartrate and Cadmium tartrate have received greater attention
on account of their ferroelectric, nonlinear optical and spectral characteristics.
The present thesis reports the linear and nonlinear aspects of these crystals and
their potential applications in the field of photonics.