Javad Zarbakhsh

Arbitrary angle waveguiding applications of two-dimensional curvilinear-lattice photonic crystals

We introduce a fresh class of photonic band-gap materials, curvilinear-lattice photonic crystals, whose distinctive feature is that their individual scatterers are arranged in a curvilinear lattice. We show that adhering to some restrictions in the acceptable lattice transformations, one can achieve omnidirectional photonic band gaps for an entire subclass of such structures. We demonstrate, designing an efficient arbitrary-angle waveguide bend, that curvilinear-lattice photonic crystals can be employed for creation of original types of nanophotonic devices.

Physical and materials aspects of photonic crystals for microwaves and millimetre waves

Abstract Experimental and numerical results on photonic crystals are presented for the frequency range 26–60 GHz. The material used is alumina where two techniques have been applied for fabricating the photonic crystals: manual assembly of alumina rods and rapid prototyping. The observed positions of the fundamental and higher photonic band gaps are in excellent agreement with the calculated results. A new type of defect in the 3D woodpile structure, is created by inserting interstitial rods. As a new 2D structure a square parquet lattice is investigated. The concept of a negative index of refraction is adressed including a model calculation and an experimental demonstration by the transmission through a slab of a 2D photonic crystal.

Method of calculating local dispersion in arbitrary photonic crystal waveguides.

We introduce a novel method to calculate the local dispersion relation in photonic crystal waveguides, based on the finite-difference time-domain simulation and filter diagonalization method (FDM). In comparison with the spatial Fourier transform method (SFT), the highly local dispersion calculations based on FDM are considerably superior and pronounced. For the first time to our knowledge, the presented numerical technique allows comparing the dispersion in straight and bent waveguides.

Local Dispersion of Guiding Modes in Photonic Crystal Waveguide Interfaces and Hetero-Structures

Recently, we have introduced a numerical method for calculating local dispersion of arbitrary shaped optical waveguides, which is based on the Finite-Difierence Time-domain and fllter diagonalization technique. In this paper we present a study of

Quality factor optimization of photonic crystal cavities through multiple multipole expansion technique and power loss integral

The Local Density of photonic States (LDOS) and Multiple Multipole Expansion technique (MME) are powerful tools in the study of spontaneous emission and calculation of photon confinement as well as efficient calculation of stationary field in planar photonic crystals. We bridge between optimization of Purcell factor and Q-factor in photonic crystal micro-cavities on one hand, and cavity power loss on the other hand. The quality factor calculated through a pulse response technique based on Finite Difference Time Domain (FDTD) simulations are compared with quality factor calculated by other approaches of LDOS and power loss. It turned out that the latter methods are more accurate and computationally less expensive. The cavity power loss is defined as the surface integration of energy density flow projected toward outside of the effective cavity volume. It is shown that size changes and shifting the neighboring rods or holes have a large impact on the mode volume and confinement. The quality factor optimization is performed for a H1- photonic crystal cavity, and mode volume investigations carried out for high Q factor arrangements. These investigations are resulted in effective structural design rules and geometrical freedom contour plots for the neighboring rods in the vicinity of the micro-cavity. These generalized design rules are suitable for further studies in other photonic micro-cavities.

OPTIMIZATION OF QUALITY FACTOR IN PHOTONIC CRYSTAL CAVITIES THROUGH FINITE DIFFERENCE TIME DOMAIN AND MULTIPOLE EXPANSION TECHNIQUE

Local density of photonic states calculation based on multipole expansion method is a powerful tool for studying spontaneous emission and calculation of photon confinement in photonic crystal cavities. Using multipole expansion method, we calculate local density of states and quality factor of a two-dimensional three angle photonic crystal cavity. We also compare this quality factor result with the one calculated using finite difference time domain of a pulse response. It turns out that the local density of states calculation is more accurate and computationally less expensive. It is shown that shifting and changing the size of neighboring cylinders in the vicinity of photonic crystal cavity has a large impact on the mode volume and confinement. It is also described how the increasing of quality factor can be split up into local optimization of neighboring rods and the effect of increasing the number of photonic crystal layers, which exponentially increases the quality factor. This finding strongly suggests that the number of layers can be excluded from an optimization procedure. We also present structural design rules and geometrical freedom contour plots for the neighboring cylinders. These design rules can be used in further optimization of photonic crystal cavities.

Simulation of intensity of single-mode Photonic Crystal Fiber Laser

In this paper shown that absorbed pump intensity and amplified signal intensity of single-mode Photonic Crystal Fiber Laser are about approximation 10 times more than absorbed pump intensity and amplified signal intensity of single-mode of Fiber Laser.

Improving the Impedance Matching in Photonic Crystal Waveguides

Summary form only given: We demonstrate that the dispersion of guided propagating modes in certain photonic crystal waveguides (PCWGs) can be kept constant when the waveguides structure changes with distance. This suggests that the principle of constant group velocity may be utilized to improve impedance matching between different types of PCWGs while at the same time providing significant design flexibility. We illustrate this principle through the design of several efficient coupling structures between two different PCWGs via a local density of state (LDOS) and Fourier transform analysis of the associate electromagnetic fields. The couplers consist of heterostructures whose individual sections exhibit rather distinct structural parameters. Furthermore, we compare these structures to an adiabatic coupler

Study of local dispersion in photonic crystal waveguide interfaces and hetero-structures

We have recently introduced a novel method to calculate local dispersion relation based on the Finite-Difference Time-domain and filter diagonalization method, which is suitable for local study of dispersion in optical waveguide, especially for the cases of non-periodic, curvilinear, and finite waveguides. In this paper, this approach is applied to study the photonic crystal waveguides at interfaces and double hetero-structure waveguides. We also studied the stretching effect, which is increasing the lateral distance between neighboring rods along guiding direction on band gap. Hybrid modes at interface are results of superposition of existing modes in adjacent waveguides. The results present a clear picture of localization mechanism of cavity modes and the transmission in the double-hetero-structures.

Local Dispersion in 2D Photonic Crystals Using Filter Diagonalization Method

Local dispersion in Photonic Crystals (PC) is calculated using the advanced filter diagonalization method and compared to the traditional spatial Fourier transform of the field distribution.