Salah S. A. Obayya

Ultra-high tunable liquid crystal-plasmonic photonic crystal fiber polarization filter.

A novel ultra-high tunable photonic crystal fiber (PCF) polarization filter is proposed and analyzed using finite element method. The suggested design has a central hole infiltrated with a nematic liquid crystal (NLC) that offers high tunability with temperature and external electric field. Moreover, the PCF is selectively filled with metal wires into cladding air holes. Results show that the resonance losses and wavelengths are different in x and y polarized directions depending on the rotation angle φ of the NLC. The reported filter of compact device length 0.5 mm can achieve 600 dB / cm resonance losses at φ = 90° for x-polarized mode at communication wavelength of 1300 mm with low losses of 0.00751 dB / cm for y-polarized mode. However, resonance losses of 157.71 dB / cm at φ = 0° can be achieved for y-polarized mode at the same wavelength with low losses of 0.092 dB / cm for x-polarized mode.

Highly Sensitive Plasmonic Photonic Crystal Temperature Sensor Filled With Liquid Crystal

A novel highly sensitive surface plasmon resonance-based liquid crystal (LC) photonic crystal fiber (PCF) temperature sensor is presented and studied. Through this letter, the coupling characteristics between the core guided mode inside the PCF core infiltrated with nematic LC and surface plasmon mode on the surface of nano gold wire are studied in detail. The structural geometrical parameters of the proposed design, such as number of metal rods, core diameter, and metal rod diameter are optimized to achieve highly temperature sensitivity. The suggested sensor of compact device length of 20 μm proved to surpass the recent sensors with high sensitivity of 10 nm/°C. The results are calculated using a full-vectorial finite-element method with irregular meshing capabilities and perfectly matched layer boundary conditions.

Fully Integrated AND and OR Optical Logic Gates

We propose two novel designs of compact, linear, and all-optical OR and AND logic gates based on photonic crystal architecture. The proposed devices are formed by the combination of the ring cavities and Y-shape line defect coupler placed between two waveguides. The performance of the proposed logic gates has been analyzed and investigated using finite difference time domain method. The suggested design for AND gate offers ON to OFF logic level contrast ratio of not less than 6 dB and the suggested design for OR gate offers transmitted power of not less than 0.5. On top of that, the proposed OR and AND logic gates can operate at bit rates of around 0.5 and 0.208 Tb/s, respectively. Further, the calculated fabrication tolerances of the suggested devices show that the rods radii of the ring cavities need to be controlled with no more than ±10% and ±3% fabrication errors for optical OR and AND gates, respectively. It is expected that such designs have the potential to be key components for future photonic integrated circuits due to their simplicity and small size.

Polarization splitter based on soft glass nematic liquid crystal photonic crystal fiber

A novel design of a polarization splitter based on index-guiding soft glass nematic liquid crystal (NLC) photonic crystal fiber is proposed and analyzed. The simulation results are obtained using the full-vectorial finite-difference modal solution along with the full-vectorial finite-difference beam propagation method. The numerical results reveal that the suggested splitter of length 8.227 mm can provide low crosstalk of better than -20 dB with great bandwidths of 30 nm and 75 nm for the quasi TE and TM modes, respectively. In addition, the reported splitter has a tolerance of ±3% in its length, which makes the design less sensitive to the perturbation introduced during the fabrication process.

Ultrashort silica liquid crystal photonic crystal fiber polarization rotator

In this Letter, an ultra-compact polarization rotator (PR) based on silica photonic crystal fiber with liquid crystal core is introduced and analyzed using full-vectorial finite difference approaches. The analyzed parameters of the suggested PR are the conversion length, modal hybridness, power conversion and crosstalk. In addition, the fabrication tolerance analysis of the reported design is investigated in detail. The proposed PR has an ultra-compact device length of 4.085 μm and an almost 100% polarization conversion ratio.

Design of passive polarization rotator based on silica photonic crystal fiber

We propose and analyze a novel (to the best of our knowledge) design of a polarization rotator (PR) based on silica photonic crystal fiber. The proposed design has a rectangular core region with a slanted sidewall. The simulation results are obtained using the full vectorial finite difference method as well as the full vectorial finite difference beam propagation method. The numerical results reveal that the suggested PR can provide a nearly 100% polarization conversion ratio with a device length of 3102 μm.

Modal Properties of an Index Guiding Nematic Liquid Crystal Based Photonic Crystal Fiber

This paper presents the results of the modal analysis of an index guiding soft glass photonic crystal fiber infiltrated with a nematic liquid crystal (NLC-PCF). The modal analysis is carried out using the full vectorial finite difference method which is capable of dealing accurately with anisotropic waveguide problems. The analyzed parameters are the effective index, birefringence, dispersion, effective mode area, and confinement losses for the two fundamental polarized modes. The effects of the structure geometrical parameters, rotation angle of the director of the NLC and temperature on the modal properties are investigated. The numerical results reveal that the proposed design offers high birefringence of 0.012 at the operating wavelength 1.55 mum with low losses for the two polarized modes. In addition, the structure is tailored to obtain a flat dispersion over a wide range of wavelengths with high birefringence.

Improved design of a polarization converter based on semiconductor optical waveguide bends

By using an efficient vector finite-element-based beam-propagation method, we present an improved design of a polarization converter. This design relies on the use of a single-section deeply etched bent semiconductor waveguide with slanted sidewalls. By careful adjustment of the bend radius, the waveguide width, and the sidewall angle we obtained a nearly 100% polarization conversion ratio with no appreciable radiation loss and a bending angle of less than 180 degrees .

Proposal of an Ultracompact CMOS-Compatible TE-/TM-Pass Polarizer Based on SoI Platform

An all-dielectric transverse electric (TE)-/transverse magnetic (TM)-pass polarizer based on silicon-on-insulator (SoI) is proposed and analyzed. The symmetric etching of the silicon nanowire with specific values allows the cutoff of the undesired polarization state while the other is propagated with minimal losses. The proposed SoI polarizer can achieve 26- and 30-dB extinction ratios and 0.4-dB insertion losses for both TE- and TM-pass polarizers, respectively, with a very compact device length as short as 2.5 μm. The polarizer maintains <;1-dB insertion loss and >20-dB extinction ratio over a wide wavelength range of 1.454-1.68 μm. Fabrication of the introduced device is compatible with standard CMOS fabrication process.

Analysis of Polarization Rotator Based on Nematic Liquid Crystal Photonic Crystal Fiber

In this paper, the performance of high-tunable polarization rotator (PR) based on nematic liquid crystal (NLC) photonic crystal fiber is reported. The tunability of the proposed PR results from the change of the optical properties of the NLC with the temperature and external electric field. The influence of the different structure geometrical parameters, rotation angle of the director of the NLC, temperature and operating wavelength on the PR performance is investigated. The numerical results reveal that the suggested PR can provide a strong polarization conversion ratio of 99.81% with a device length of 1072 ¿m. It is expected that over the 1.53-1.6 ¿ m wavelength range, polarization conversion would be more than 99%. The simulation results are evaluated using the full-vectorial finite-difference method and confirmed by the full-vectorial finite-difference beam-propagation method.