Mehdi Tajaldini

Simulation of an Ultra-Compact Multimode Interference Power Splitter Based on Kerr Nonlinear Effect

We propose an ultra-compact multimode interference (MMI) power splitter based on the Kerr nonlinear effect from simulations using modal propagation analysis. Crystalline polydiacetylene is used as the core layer to allow for the creation of a power splitter with a high number of outputs with the shortest possible multimode waveguide length operating in the nonlinear regime. The 11 high-contrast, high-resolution images at the end of the multimode waveguide in the simulated power splitter have a high power balance, whereas access to a high number of self-images is not possible under the linear regime in the proposed length range. The compact dimensions and ideal performance of the device are established according to optimized parameters. The proposed regime can be extended to the design of M × N power splitters. The results of this study indicate that nonlinear modal propagation analysis solves the miniaturization problem for all-optical devices based on MMI couplers to achieve multiple functions in a compact planar integrated circuit and also overcomes the limitations of previously proposed methods for nonlinear MMI. The results are verified using a numerical method.

The influence of nonlinear modal propagation analysis on MMI power splitters for miniaturization

This study investigates a method to access the power splitting performances of multimode interference waveguides based on analytical nonlinear modal propagation analysis method in the presence of the Kerr nonlinear effect for device miniaturization. Nonlinear multimode interference waveguide has been already reported in a few work based on beam propagation analysis (BPM) for make a special path with intense input for switching purposes. BPM method does not seem a capable method for study the multimode waveguide performance in small lengths. Therefore, we established the nonlinear modal propagation analysis on the way that is determined based on the propagation of all nonlinear guided modes throughout the medium whereas this shows the amplitude and phase changes of the guided modes. In fact mentioned change lead to induction of nonlinearity on original guided modes and make them nonlinear. In this paper, the nonlinear guided modes which are excitedfrom input beam are measured with solve the nonlinear differential equation. Intensity distribution among the multimode waveguide as a simulation tool assist us to show the possibility to access to 1×N power splitters whereas they operate on small lengths in comparison with past reports in linear regimes. In fact the formation of parallel self- images determined the outputs for splitter and the resolution and contrast of image show the uniformity and insertion loss that result demonstrate desirable uniformity and insertion loss so that miniaturization does not decrease the performance. Also the simulation result shows proposed active device is more sensitive to the input intensity. This sensitive can be a foundation for propose an arbitrary power splitter ratio devices.

Nonlinear modal propagation analysis method in multimode interference coupler for operation development

In this study, we propose a novel approach that is called nonlinear modal propagation analysis method (NMPA) in MMI coupler via the enhances of nonlinear wave propagation in terms of guided modes interferences in nonlinear regimes, such that the modal fields are measurable at any point of coupler and output facets. Then, the ultra-short MMI coupler is optimized as a building block in micro ring resonator to investigate the method efficiency against the already used method. Modeling results demonstrate more efficiency and accuracy in shorter lengths of multimode interference coupler. Therefore, NMPA can be used as a method to study the compact dimension coupler and for developing the performance in applications. Furthermore, the possibility of access tothe all-optical switching is assumed due to one continuous MMI for proof of the development of performances in nonlinear regimes.

Proposal of a novel method for all optical switching with MMI coupler

This paper, propose a novel approach to access all optical switching performance usable in telecommunications and photonic signal processing circuits by one continuous MMI coupler under a nonlinear regime to achieve the switching at smallest length of Multimode interference waveguide. In past methods, there have been MMI switch with length about a few millimeters, but in this paper an MMI is presented for switching purposes with a length less than 100μm. In this approach, the wave propagation is studied base on MPA method. The nonlinear wave equation in presence of Kerr nonlinear effect is solved as a set of multiple coupled nonlinear equations, so each equations are related to one of guided modes in Multimode waveguide. With ability of calculating the electric field at the outputs channels, we are able to optimize the Multimode waveguide in terms of length. switching is performable with a variation of input intensity or electric field, thus the output fields have been measured with 105 different amounts of input electric fields for each lengths which are switching candidates, then switching operation is appeared in special length with its dependence input electric fields that each electric fields relate to switch the light to bar or cross outputs, this switch is the outstanding proposal for new all optical digital signal processing due to the compact size.

Graphene based multimode interference coupler as an optical refractive index sensor based on nonlinear modal propagation analysis

The objective of this study is to propose and introduce nonlinear modal propagation analysis (NMPA) method being a viable way to study the application of graphene based multimode interference (MMI) coupler as an optical refractive index sensor. The purpose of using graphene in this study is because of its high optical nonlinearity as well as having a small bandgap due to its thin layer. The graphene based sensor can be tuned for highest sensitivity in wavelength and refractive index to detect the clad material. Graphene will act as the core of the sensor which will be placed on top of the sample. The clad refractive index value can be obtained by observing and analyzing the change in the output facet intensity of the sensor. The result also shows that the sensor has high sensitivity due to the usage of graphene and nonlinear region.

Self-phase modulation on a graphene used waveguide

In this paper, we study the self-phase modulation on a sub-micro graphene waveguide to show the nonlinear optical properties of graphene. Self-modulation is one of the most popular nonlinear effects that has been observed due to selfinfluence of a mode propagation in third-order materials. This effects is capable to demonstrate the nonlinearity based the structure. Our study is aimed to show the appearance of SPM in considered waveguide as a common effect of nonlinear refraction to proof the capability of graphen on apply the based waveguide in nonlinear regime to access the desired parameters such as dimension and insertion power. An interest aspect is placed in this simulation may be conversion step-index to grade-index due to change from linear to the nonlinear that causes high confinement of light in waveguide.

Arbitrary-ratio power splitter based on nonlinear multimode interference coupler

We propose an ultra-compact multimode interference (MMI) power splitter based on nonlinear effects from simulations using nonlinear modal propagation analysis (NMPA) cooperation with finite difference Method (FDM) to access free choice of splitting ratio. Conventional multimode interference power splitter could only obtain a few discrete ratios. The power splitting ratio may be adjusted continuously while the input set power is varying by a tunable laser. In fact, using an ultra- compact MMI with a simple structure that is launched by a tunable nonlinear input fulfills the problem of arbitrary-ratio in integrated photonics circuits. Silicon on insulator (SOI) is used as the offered material due to the high contrast refractive index and Centro symmetric properties. The high-resolution images at the end of the multimode waveguide in the simulated power splitter have a high power balance, whereas access to a free choice of splitting ratio is not possible under the linear regime in the proposed length range e...

All-optical universal logic gates on nonlinear multimode interference coupler using tunable input intensity

The theory of Nonlinear Modal Propagation Analysis Method (NMPA) have shown significant features of nonlinear multimode interference (MMI) coupler with compact dimension and when launched near the threshold of nonlinearity. Moreover, NMPA have the potential to allow studying the nonlinear MMI based the modal interference to explorer the phenomenon that what happen due to the natural of multimode region. Proposal of all-optical switch based NMPA has approved its capability to achieving the all-optical gates. All-optical gates have attracted increasing attention due to their practical utility in all-optical signal processing networks and systems. Nonlinear multimode interference devices could apply as universal all-optical gates due to significant features that NMPA introduce them. In this Paper, we present a novel Ultra-compact MMI coupler based on NMPA method in low intensity compared to last reports either as a novel design method and potential application for optical NAND, NOR as universal gates on sing...

Self-focusing appearance in ultra-compact 3×3 multimode interference coupler based on silicon on insulator

The study of multimode interference (MMI) couplers in silicon waveguides is limited by the high index contrast, especially when operated in nonlinear regime. In low index contrast, the common method is beam propagation method (BPM) that is based on several algorithms which propose a simple numerical method, but, in nonlinear high index contrast, the modal propagation analysis based on finite difference method (FDM) is a rigorous method, and high index contrast is a super benefit to confine the wave in waveguide in the maximum rate to appearance the self-focusing in highly ultra-compact size. In this paper, we investigate the nonlinear effect in high index contrast structure of silicon on insulator (SIO) 3×3 multimode coupler. Moreover, by simulation of the wave propagation while the input intensities are increasing simultaneously, the appearance of self-focusing are demonstrated. The results show capability of nonlinear modal propagation by FDM numerical solution. Wave propagation in multimode region accomplished with the output electric field indicate the good efficiency for the considered purposes.

Proposal of ultra-compact NAND/NOR/XNOR all-optical logic gatesbased on a nonlinear 3x1 multimode interference

We present a highly miniaturized multimode interference (MMI) coupler based on nonlinear modal propagation analysis (NMPA) method as a novel design method and potential application for optical NAND, NOR and XNOR logic gates for Boolean logic signal processing devices. Crystalline polydiacetylene is used to allow the appearances of nonlinear effects in low input intensities and ultra- short length to control the MMI coupler as an active device to access light switching due to its high nonlinear susceptibility. We consider a 10x33 μm2 MMI structure with three inputs and one output. Notably, the access facets are single-mode waveguides with sub-micron width. The center input contributes to control the induced light propagation in MMI by intensity variation whereas others could be launched by particular intensity when they are ON and 0 in OFF. Output intensity is analyzed in various sets of inputs to show the capability of Boolean logic gates, the contrast between ON and OFF is calculated on mentioned gates to present the efficiency. Good operation in low intensity and highly miniaturized MMI coupler is observed. Furthermore, nonlinear effects could be realized through the modal interferences. The issue of high insertion loss is addressed with a 3×3 upgraded coupler. Furthermore, the main significant aspect of this paper is simulating an MMI coupler that is launched by three nonlinear inputs, simultaneously, whereas last presents have never studied more than one input in nonlinear regimes.