The miniaturization of photonic components in integrated optic waveguide devices to microscale platform has attracted enormous attention from the researchers and entrepreneurs. In this paper, we present and report a comparative study of photonic integrated planar waveguide based couplers using a mathematical model based on sinusoidal mode simple effective index method (SEIM). The basic photonic integrated components such as directional coupler (DC), two mode interference (TMI) coupler and multimode interference (MMI) coupler have been designed and fabricated using the versatile SiON waveguide technology (SiON as the waveguide core material using silica waveguide). The experimental results have been compared with the SEIM based theoretical results and further verified with the commercially available software tool based on beam propagation method (BPM). With a focus towards device compactness, particular emphasis is placed on device geometry in an endeavour to achieve the same. In this direction, the theoretical and experimental results obtained have been compared with tooth shaped grating assisted geometry for these photonic components. It is found that the grating assisted structures have the beat length ~0.5 times lower than that of the conventional geometry. Further it is seen that the beat length of TMI coupler is smaller compared to the DC and MMI coupler.
The development of an evanescent waveguide optical sensor incorporating planar waveguide geometry using silicon oxynitride as the core layer on silica-silicon wafer and its implementation for detection of adulterant traces in petroleum products is presented in this paper. This work focuses on enhancement of sensitivity and analyzed by using Simple Effective Index Method (SEIM), based on sinusoidal modes. The embedded waveguide of length ~ 10,000 μm and core width ~ 50 μm have been developed using SiON technology and applied for checking adulteration so as to ensure the purity of the fuel such that the engine will give the desired performance including low emissions yielding better accuracy and high sensitivity within a very short pulse. The thin cladding layer acts as the analytes (mixture of adulterated fuel) that supports the waveguiding film having a refractive index smaller than that of the core. The main aim of this present work is to encompass a speedy choice to the time-consuming existing methods for detecting adulterated fuels, which generally requires some time to give the consequence. The developed sensor allows spot determination of the percentage concentration of adulterant in pure petrol without involving any chemical analysis. The waveguide based sensor is polarization independent and the sensitivity of the waveguide sensor is ~10 times more than that of the existing planar waveguide sensors and also 5 times more than that of asymmetric waveguide structure. Advantages include high sensitivity, simple fabrication and easy interrogation without involving the use of solvents or toxic chemicals.
The introduction of Photonic Integrated Devices (PID) for applications in high speed optical networks providing multiple services to more number of users is indispensable as this requires large scale integration (LSI) and the miniaturization of PID device components to microscale platform has attracted immense attention from the researchers and entrepreneurs. In this paper, we present a comparative study on compactness of basic PID components using tooth shaped grating assisted (TSGA) geometry. The basic PID components such as Directional Coupler (DC), two mode interference (TMI) coupler and multimode interference (MMI) coupler have been designed using TSGA geometry in the coupling region and the coupling characteristics for the same have been estimated using a mathematical model based on sinusoidal mode simple effective index method (SM-SEIM). The dependence of modal power in the coupling region on the waveguide separation gap and coupling gap refractive index has been studied. From the estimated dependences of beat length and access waveguide length on waveguide separation gap with permissible propagation loss ~0.15 dB/cm, it has been found that the grating assisted TMI coupler (GA-TMI) is ~0.5 times lower than that of grating assisted DC (GA-DC) and ~0.44 times lower than grating assisted MMI (GA-MMI) coupler. Further, it is seen that the device length including access waveguide length of GA-MMI coupler is less than that of GA-TMI coupler and GA-DC. The SM-SEIM based numerical results are then compared with beam propagation method (BPM) results obtained by using commercially available optiBPM software.
The development of a highly sensitive asymmetric planar waveguide optical sensor based on a mathematical model using leaky quasi-modes in an endeavor to measure slight changes of aqueous sucrose concentration is presented in this paper. The planar waveguide sensor has been fabricated using Silicon Oxynitride (SiON) based material with standard fabrication process such as Plasma Enhanced Chemical Vapor Deposition (PECVD) and Reactive Ion Etching (RIE) techniques. The propagation constant of fundamental modes for TE mode of the waveguide geometry have been estimated using Simple Effective Index Method (SEIM) based on sinusoidal modes. The technique is based on Evanescent Wave Sensing (EWS) scheme, inducing an effective refractive index change. The merits of this sensor are simplicity, highly sensitivity, screening the potential that it can be used for online monitoring of blood glucose levels in the near future. The sensitivity of the waveguide is ~10 times more than that of the previously reported work on planar waveguide sensors and the results obtained experimentally matches well with the obtained theoretical result.
An evanescent waveguide–based optical sensor incorporating composite planar waveguide geometry using silicon oxynitride as core layer has been designed and developed. The proposed waveguide of length ∼10,000 μm and core width ∼50 μm was embedded on silica/silicon wafer and tailored for sensing glucose concentration in aqueous solution with high waveguide sensitivity ∼0.95 , as an evidence of the design and development. We derived the dispersion relation from the wave equation of the structure for estimating the propagation constants of transverse electric and transverse magnetic modes and then modeled the sensor response to the change of the sensing layer refractive index. The enhancement of waveguide sensitivity is shown by using simple effective index method based on sinusoidal modes. The sensor structure is polarization independent. The theoretical results are in good agreement with the results obtained experimentally. The experimental results have revealed strong enhancement in terms of waveguide sensitivity which is ∼10 times more than that of the existing planar waveguide sensors and five times more than asymmetric waveguide sensor. This proposed waveguide sensor requiring minimal sample volume has the potential to realize for online monitoring of blood glucose levels in the near future.
In this paper a comprehensive study of compact conventional Directional Coupler (DC) and Multimode Interference (MMI) coupler using a numerical model based on Simple Effective Index Method (SEIM) have been presented. The coupling length of the couplers is then compared with the results obtained by using commercially available Beam Propagation Method (BPM) based software with respect to different waveguide separation gap and different coupling
gap’s refractive indices. The designed couplers are fabricated using SiON as a core and silica as a cladding. It is found
both from the experimental and theoretical results that the beat length of conventional MMI coupler is ~ 1.9 times lower than that of conventional DC.
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