Aradhana Dutta

Modeling and fabrication of evanescent waveguide-based optical sensor for sensitivity enhancement using silicon oxynitride technology

Abstract. 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.

Integrating optical glucose sensing into a planar waveguide sensor structure

A device for glucose monitoring in people with diabetes is a clinical and research priority in the recent years for its accurate self management. An extensive theoretical design and development of an optical sensor is carried out incorporating planar waveguide structure in an endeavor to measure slight changes of glucose concentration. The sensor is simple and highly sensitive and has the potential to be used for online monitoring of blood glucose levels for the diabetic patients in the near future.

Optical Waveguide Sensor as Detection Element for Lab on a Chip Sensing Application

The assessment of accurate glucose level is an important aspect in the field of clinical diagnostics. With ever-improving advances in diagnostic technology, we find that new techniques and approaches have been demonstrated for monitoring blood glucose. Addressing to this matter, the objective of this chapter is to introduce a new optical concept for measuring glucose concentration in blood plasma that involves the development of a new miniaturized technique using Poiseuille’s equation of viscous flow and light propagation through the optical waveguide. Potentially, this technique can be very useful in the management of diabetes in the near future. The advantage of this approach, with respect to other optical methods, is safe and capable of providing accurate result in terms of enhanced sensitivity. The sensor developed requires very minimal sample for its detection.

Waveguide Sensor for Detecting Adulteration in Petroleum-Based Products

Sensing technologies based on the principle of Frustrated Total Internal Reflection (FTIR) are continuously driving the development of novel applications like detecting adulteration in petroleum product. Using FTIR phenomenon, the skill highlighted in this chapter has taken advantage of emerging advances in adulteration detection technique, signifying the unique versatility of the optical waveguide core phenomenon. The sensitivity of the developed sensor to detect adulterated petroleum product is in good agreement with predictions derived from its measured sensitivity. Advantages include the ability to perform faster, more sensitive, and very short-time requirement for its measurements without involving any chemicals.

Introduction to Planar Waveguide Optical Sensor

Sensing platform based on the integrated optical planar waveguide represents an active research area. The development of optical planar waveguide sensor has largely been motivated by the need for rapid, automated devices for application in the fields of clinical diagnostics and adulteration detection. The technologies highlighted in this chapter have taken advantage of emerging advances in silicon technology and Lab on a Chip (LOC) device platform. This chapter gives an introduction of the integrated optic (IO) sensors, its characteristics, and a brief outline of works along with the scope of waveguide sensors. Furthermore, the silicon photonics fabrication platform that was used to fabricate the sensor, the optical waveguide material study as well as the impetus for the use of silicon photonics is reported in this chapter. The chapter ends with the organization of this book.

Theoretical Modeling, Design, and Development of Integrated Planar Waveguide Optical Sensor

Planar waveguide optical sensor development has principally been driven by the need for rapid, automated devices for application in the fields of clinical diagnostics and biological detection. This chapter is prepared as theoretical basis providing the basic foundation and supported by application as evidence for the sensor development. Using Maxwell’s equation, a theoretical analysis for wave propagation in planar waveguide sensor with silicon oxynitride (SiON) as the waveguide material is presented. The theoretical results are in good agreement with experimental results. Theoretical consideration, supporting calculations, and experimental results showed that the sensor can be used for online monitoring of glucose level as it requires very minimal sample volume for its detection with high sensitivity. The sensor will have a significant impact on health care in the near future.

Brief Review on Integrated Planar Waveguide-Based Optical Sensor

Planar optical waveguides are the input devices to build an integrated optical sensor. This chapter provides review made in the recent advancement of integrated optical sensor that involves guided light with substantial developments made at a very rapid pace. The basic concept and equations of electromagnetic (EM) wave theory requisite for lightwave propagation in optical waveguides are presented. The light confinement and formation of modes in the waveguide are qualitatively explained, considering a slab waveguide. Maxwell’s equations, boundary conditions, are described as they form the basis for the following chapters. Theoretical consideration and supportive calculation to understand the basic properties of optical waveguide is presented for a step-index waveguide. Further, the derivation of dispersion equations is explained in detail in order to understand the dispersion characteristics of optical waveguide. Rigorous three-dimensional analysis usually requires numerical calculations, and therefore, this chapter presents several methods such as finite element method, finite difference time domain, and beam propagation method necessary for mode analysis of optical waveguide. The detection of glucose level in blood is a highly researched area in the quest for a sensor that can give accurate measurements, in short time, with minimum invasiveness. Although several optical techniques are being explored for glucose detection including infrared spectroscopy however, there are limitations to these techniques and involve complications. A short review is done on available medical and engineering concepts and attempt is made to discuss how far these can be applied to optical waveguide-based sensor with fine accuracy and high sensitivity.

Design and fabrication of compact integrated optic waveguide coupler using SiON/SiO2 material

A comprehensive study on development of silicon oxynitride/silica based compact photonic components is presented. Plasma Enhanced Chemical Vapor Deposition technique and Reactive Ion Etching was used for development of compact directional coupler (DC) and two mode interference (TMI) coupler using a numerical model based on Simple Effective Index Method. It is found that coupling length of the conventional TMI coupler is 1.3 times lower than the conventional DC. In addition, numerical and experimental results are compared with Beam Propagation Method.

Fabrication and comprehensive study of silicon oxynitride based compact directional coupler and multimode interference coupler

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.

Comparative study on compact planar waveguide based photonic integrated couplers using simple effective index method

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.