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.
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.
In this study, we propose an all-optical sensor based on consideration the nonlinear effects on modal propagation and output intensity based on ultra-compact nonlinear multimode interference (NLMMI) coupler. The sensor can be tuned to highest sensitivity in the wavelength and refractive index ranges sufficient to detect water- soluble chemical, air pollutions, and heart operation. The results indicate high output sensitivity to input wavelength. This sensitivity guides us to propose a wave sensor both transverse and longitudinal waves such as acoustic and light wave, when an external wave interacts with input waveguide. For instance, this sensor can be implemented by long input that inserted in the land, then any wave could detected from earth. The visible changes of intensity at output facet in various surrounding layer refractive index show the high sensitivity to the refractive index of surrounding layer that is foundation of introducing a sensor. Also, the results show the high distinguished changes on modal expansion and output throat distribution in various refractive indices of surrounding layer.
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.
In this study, we propose an all optical sensor based on nonlinearity in a multimode
interference coupler. The sensor can be tuned to highest sensitivity in the refractive index ranges
sufficient to detect protein- based molecules or other water- soluble chemical or biological
materials. The nonlinear regimes show the capability to operate on any choice of materials for slab
waveguide even conventional glass. The Kerr nonlinear effect is considered as the nonlinear effect
for third order nonlinearity materials; this effect is studied in the multimode waveguide with MPA
method that promises to investigate the coupler in small lengths. The visible changes of field
profile at output facet in various surrounding layer refractive index show the high sensitivity to the
refractive index of surrounding layer that is foundation of introducing a sensor. Also, the result
show the high distinguished changes on output intensity in various refractive index of surrounding
layer even in conventional glass as a chosen material for coupler. To the best of our knowledge
this is the first time that a nonlinear MMI in a few micrometers is proposed as a robustness sensor.
In fact, this paper brings a useful and powerful way to progress the all optical sensors based on
MMI couplers.
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.
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.
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