Optical Waveguide Theory

A topical review of numerical and experimental studies of supercontinuum generation in photonic crystal fiber is presented over the full range of experimentally reported parameters, from the femtosecond to the continuous-wave regime. Results from numerical simulations are used to discuss the temporal and spectral characteristics of the supercontinuum, and to interpret the physics of the underlying spectral broadening processes. Particular attention is given to the case of supercontinuum generation seeded by femtosecond pulses in the anomalous group velocity dispersion regime of photonic crystal fiber, where the processes of soliton fission, stimulated Raman scattering, and dispersive wave generation are reviewed in detail. The corresponding intensity and phase stability properties of the supercontinuum spectra generated under different conditions are also discussed.

Supercontinuum generation, photonic crystal fiber

http://ieeexplore.ieee.org/iel5/5/31325/01456922.pdf

An introduction to optical waveguides

A microchannel incorporated photonic crystal fiber (PCF)-based surface plasmon resonance (SPR) sensor for detection of low refractive index (RI) at near-infrared wavelength is presented in this paper. To attain a simple and practically feasible mechanism, plasmonic material gold (Au) and sensing medium are placed outside the fiber. A thin layer of TiO2 is employed as an adhesive layer to strongly attach the Au with the silica glass. In the sensing range of 1.22 to 1.37, maximum sensitivities of 51,000 nm/RIU (RI unit) and 1872  RIU−1 are obtained with resolutions of 1.96×10−6 and 9.09×10−6 RIUs using wavelength and amplitude interrogation methods, respectively. To the best of the authors’ knowledge, the obtained maximum wavelength sensitivity and resolution are the highest among reported PCF-based SPR sensors to date. The sensor also exhibits a maximum figure of merit of 566. Therefore, the proposed sensor would be an excellent candidate for a wide range of RI detection with higher accuracy for applications such as pharmaceutical inspection and leakage monitoring, bio-sensing, and other low RI analytes.

Microchannel-based plasmonic refractive index sensor for low refractive index detection

I use the direct far-field method to measure the mode-field diameter of a single-mode fiber with an expanded uncertainty of 30 nm, with a coverage factor of 2. For a step-index fiber with a mode-field diameter of approximately 9 mum, the major sources of uncertainty are nonlinearity in the electronics, angular errors and scattered light in the apparatus, and the polarization and noncircularity of the mode of the fiber. The paper concludes by showing an inconsistency in the derivation of the far-field expression for mode-field diameter.

Mode-Field Diameter of Single-Mode Optical Fiber by Far-Field Scanning

We have recently developed a simple analytical model to study propagation characteristics of microstructured optical fibers (MOFs). We have used this model to study splice losses between two MOFs and also between an MOF and a conventional fiber. We have also presented here the results on evolution of fundamental mode from near-field to far-field, the effective mode area and the beam divergence using this model. Comparisons with available experimental and modeling results have also been included.

Characteristic of microstructured optical fibers: an analytical approach

Low-loss splicing of index-guiding microstructured optical fibers (MOFs) and conventional single-mode fibers (SMFs) can be achieved by enlarging the mode field diameter of MOFs, which leads to an optimum mode field match at the joint interface. We study analytically the low-loss fusion splicing between an MOF and an SMF by expanding the modal field of MOF, using the controlled air-hole collapse method. Our method is simple and offers analytical solution for light coupling between MOFs and SMFs. Comparisons with available experimental and simulation results have also been included.

Splicing of index-guiding microstructured optical fibers and single-mode fibers by controlled air-hole collapse: an analytical approach

On the mode field diameter of microstructured optical fibers

Silica based optical waveguides are restricted by the silica material parameters such as low nonlinear refractive index and transparency below 3.0 μm. These limitations have led to investigation of new materials with high nonlinear refractive index and transparency in the mid-infrared (IR) region such as tellurite glasses, possessing considerable interest for a broad range of applications in the domain of optical telecommunication and sensing due to their wealth of excellent optical characteristics. We aim to explore the fundamental propagation properties of tellurite glasses based high-index core microstructured optical fibers (MOFs) by using the field model to judge the feasibility of using nonsilica glasses as the background material. Comparison with available numerical simulation results also has been included.

Modal analysis of high-index core tellurite glass microstructured optical fibers in infrared regime

The excellent propagation properties of square-lattice microstructured optical fibers (MOFs) have been widely recognized. We generalized our recently developed analytical field model (Sharma and Sharma, 2016), for index-guiding MOFs with square-lattice of circular air-holes in the photonic crystal cladding. Using the field model, we have studied the propagation properties of the fundamental mode of index-guiding square-lattice MOFs with different hole-to-hole spacing and the air-hole diameter. Results for the modal effective index, near and the far-field patterns and the group-velocity dispersion have been included. The evolution of the mode shape has been investigated in transition from the near to the far-field domain. We have also studied the splice losses between two identical square-lattice MOFs and also between an MOF and a traditional step-index single-mode fiber. Comparisons with available numerical simulation results, e.g., those based on the full-vector finite element method have also been included.

Dinesh Kumar Sharma

Papers

Characteristic of microstructured optical fibers: an analytical approach

Splicing of index-guiding microstructured optical fibers and single-mode fibers by controlled air-hole collapse: an analytical approach

On the mode field diameter of microstructured optical fibers

Modal analysis of high-index core tellurite glass microstructured optical fibers in infrared regime

Characteristics of solid-core square-lattice microstructured optical fibers using an analytical field model