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In this paper, we put forward comparison between optical parameters of square symmetric lattice, triangular symmetric lattice and asymmetric lattice Photonic Crystal Fiber. Simulation using COMSOL Multiphysics illustrates that the designed fibers are characterized by low dispersion and very high non linearity which makes them suitable fibers for the realisation of super continuum generation at lower wavelengths with low input power requirements. Among the designed fibers, triangular lattice Photonic Crystal Fibers has very high non linearity of 2235 W−1 m−1 at 0.8μm wavelength. The structures found to have zero dispersion wavelengths closer to telecommunication window.

We consider an optical pulse propagating in a tapered photonic crystal fiber (PCF) wherein dispersion as well as nonlinearity varies along the propagation direction. The generalized nonlinear Schrödinger equation aptly models the pulse propagation in such a PCF. The design of the tapered PCF is based on the analytical results, which demand that the dispersion decrease exponentially and the nonlinearity increase exponentially. In this paper, we adopt the generalized projection operator method for deriving the pulse-parameter equations of the Lagrangian variation method and the collective variable method. Besides, we consider another pulse profile called raised cosine (RC), which is aimed at replacing the conventional hyperbolic secant pulse. From the detailed results, we infer that the initial RC pulse evolves into a hyperbolic secant pulse. Further, in order to minimize the input power requirement, we employ the idea of replacing the solid core in the PCF with chloroform. In addition to the single pulse compression, we also investigate the possibility of multisoliton pulse compression. Here, we consider eight chirped hyperbolic secant pulses as input and generate a train of ultrashort pulses at 850 nm based on the chirped multisoliton pulse compression. In a similar way, we extend this pulse compression with eight RC pulses.

We design a large mode area (LMA) micro-cladding leakage channel fiber (LCF) with an octagonal shaped core for 1.064 μm wavelength. Our numerical simulation shows that very low bending loss at small bend radius can be achieved by scaling up the micro-cladding elements of LCF. Further, the proposed fiber exhibits novel properties such as large effective area (1287 μm2) and very low bending loss of 5.58 × 10−3 dB/m for a bending radius of 5 cm. These interesting properties of the proposed LCF pave the way for developing a compact high power fiber laser and amplifier.

We design a ten-fold photonic quasi-crystal fiber using finite element method. Further, we explore various optical characteristics and exploit them for realizing a biosensor. We achieve a maximum refractive index sensitivity of 29000 nm/RIU and a resolution of 3.4 × 10−6 RIU a sensing range of 1.47–1.48.

We design a solid-core photonic quasi-crystal fiber (SC-PQF) of 6-fold for a wide range of operating wavelengths from 0.3 to 5 μm. Further, we explore the various optical properties, namely, birefringence, group velocity dispersion, confinement loss and nonlinearity for the proposed SC-PQF. We achieve a low dispersion of −13 ps2/km and a high nonlinearity of 480 W−1km−1 for 0.3 μm wavelength. By exploiting these optical properties, we numerically demonstrate the generation of few-cycle optical pulses of pulse width 4.7 fs from 30 fs input pulse using the higher order soliton pulse compression technique.

Synthetic Aperture Radar (SAR) images are inherently degraded due to the coherent nature of the scattering phenomena called speckle. The presence of speckle decreases the utility of the SAR images by reducing the ability to detect ground objects. It affects the quality of the image adversely and hampers the observation of vital and crucial information present in the image. In this paper, we present speckle noise suppression techniques using wavelet decomposition and ICA methods. The algorithms viz., Projection Onto Approximation Coefficients (POAC), Projection Onto Span Algorithm (POSA) and Independent Component Analysis (ICA) are implemented on real SAR images and their results are tabulated. A comparison is made with standard speckle filters such as Lee filter, Frost filters, etc. The performance of our methods is measured in terms of Peak Signal-to-Noise Ratio (PSNR) values.

We design a 10-fold photonic quasi-crystal fiber (PQF) for analyzing the efficiency of second harmonic generation (SHG). In this study we emphasize on lowering two factors, namely, overlap area and wave-vector mismatch which determine the efficiency of SHG. We find a trade off variation between these two factors with increment in pitch. Finally we optimize the relative efficiency of SHG as 84.87 %W−1cm−2 for a 10-fold PQF, which is 35% higher than that of earlier reported relative efficiency of 6-fold PQF (62.96% W−1cm−2).

A solid core photonic quasi-crystal fiber (PQF) is a novel microstructured optical fiber which could provide a large nonlinearity and a low dispersion, which, in turn, could be exploited for generating few cycle laser pulses. We look for the hitherto mentioned optical properties in the proposed PQF by carefully changing the geometrical parameters, namely, core diameter and the pitch. We report a large nonlinearity (γ = 588.2993 W−1m−1) and a low dispersion (≈ 0.095 ps/nm.m) for operating wavelengths from 1200 to 2000 nm.

We design a photonic silicon nanowire embedded microstructured optical fiber which is a special class of waveguide whose core diameter is of subwavelength or nanometer size with the air holes in the cladding. We study the optical waveguiding properties, namely, waveguide dispersions and effective nonlinearity by varying the core diameter. The results reveal that the air-clad silicon subwavelength nanowire exhibits several interesting properties such as a large normal dispersion (82385 ps2/km) for 300 nm core diameter and a large anomalous dispersion (-6817.3 ps2/km) for 500 nm core diameter at 1.95 µm wavelength. The structure provides a large nonlinearity (3648 1/Wm) at 0.450 µm wavelength for 300 nm core diameter. These enhanced optical properties might find suitable for various nonlinear applications that include the generation of fewcycle pulses, supercontinuum generation and optical processing.

Using finite element method (FEM), we design a silicon nanowire embedded circular photonic crystal fiber (SN-CPCF). We study the different optical properties at 1550 nm. We observe that the fiber switches from anomalous dispersion to normal dispersion regime as and when the core diameter decreases from 400 nm to 300 nm. We obtain a large normal group velocity dispersion (14320 ps2/km) at 300 nm core diameter whereas we obtain a large anomalous group velocity dispersion (-5256 ps2/km) for 400 nm core diameter. In addition, the proposed fiber offers a less third order dispersion (-110 ps3/km) and a small effective mode area (0.053 μm2) which results in a large effective nonlinearity (690 W-1m-1) at 300 nm core diameter. These enhanced optical properties make the silicon nanophotonic wire an ideal platform for a variety of nonlinear applications.

In this paper, we generate bright as well as dark soliton type ultrashort laser pulses in a photonic nanowire. The pulse evolution in the photonic nanowire is described by higher order nonlinear Schrodinger equation with an additional effect relating to the nonlinear change of group velocity, which, in turn, is proportional to the field intensity. The pulse evolution equation is solved by coupled amplitude-phase method. Further, we calculate the minimum power required for realizing the ultrashort laser pulses. The main crux of this work stems from the generation of ultrashort pulses by an entirely new nonlinear effect involving change of group velocity.

We consider the optical pulse propagation in a tapered photonic crystal fiber (PCF) wherein dispersion as well as nonlinearity varies along the propagation direction. The generalized nonlinear Schrodinger equation aptly models the pulse propagation in such a PCF. The design of the tapered PCF is based on the analytical results which demand that the dispersion decrease exponentially and the nonlinearity increase exponentially. By employing the self-similar scaling analysis, we have already proposed the efficient pulse compression scheme with the chirped soliton. In order to get more insight into the dynamics of the pulses (the variations in the amplitude, pulse width and chirp) while being compressed, we adopt the generalized projection operator method (POM) which, in turn, helps arrive at two different sets of pulse parameter equations of Lagrangian variation method (LVM) and collective variable method (CVM).

We theoretically investigate the generation of linearly chirped solitary pulse in photonic crystal fiber (PCF) to obtain very short pulses than adiabatic compression, wherein the effective dispersion decreases but the nonlinearity increases exponentially, by using the self-similar analysis. The dispersion and nonlinearity varying nonlinear Schrodinger (NLS) equation aptly models the pulse propagation in such PCF. Based on the analytical results, we propose the efficient pulse compressor which generates chirp and pedestal free ultrashort pulses at 850 nm in newly designed photonic crystal fiber (PCF) structures. In addition, we apply the projection operator method to derive the pulse parameter equations which indeed very clearly explain the behavior of the adiabatic and self-similar compressed pulses in different parts of the PCF structures. The analytical results exactly match with the results obtained by the projection operator method. Further, we also adopt the split-step Fourier algorithm to investigate the pulse compression process in PCF and we find that the results obtained from direct numerical experiments also exactly match with those of analytical and semi-analytical results. The main advantage of the proposed pulse compressor based on self-similar technique is that the compression factor can be increased enormously when compared to the adiabatic compression.

We investigate the effects of higher order dispersion on the self-similar optical pulse compression in nonlinear fiber Bragg gratings with exponentially decreasing dispersion.

We propose the high degree pulse compressor based on the chirped higher order soliton pulses in the exponentially decreasing dispersion.

We demonstrate almost chirp-fee and pedestal-free optical pulse compression in nonlinear fiber Bragg gratings with exponentially decreasing dispersion. The exponential profile is well approximated by a number of gratings with constant dispersion.

We present the compression of chirped Bragg solitary pulses near photonic band gap of nonlinear fiber Bragg gratings with exponentially decreasing dispersion. Compression factor of the proposed scheme is two times larger than adiabatic compression.