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Main issues of large-scale and large-area production of the solar cell are the high cost of fabrication due to the involvement of costly and sophisticated equipment and the use of costly materials in fabrication. Here, an effective and low-cost approach has been proposed for the fabrication of reduced graphene oxide (rGO)–ZnO/silicon heterostructure solar cells. The hybrid composite of rGO–ZnO has been synthesized by using a low-cost chemical method and deposited on a pcSi substrate by a sol-gel process for application in heterojunction solar cells. The morphology, crystal phase, surface functional groups, and optoelectronic properties of the heterostructure have been investigated by using SEM, XRD, the Fourier transform infrared (FTIR) spectroscopy, the Raman spectroscopy, and the UV-vis spectroscopy. The ${I}$ – ${V}$ characteristics of the fabricated heterojunction cell show a power conversion efficiency of 4.35% ( $V_{\text {oc}}= {0.51}$ V, ${J}_{\text {sc}}= {14.47}$ mA $\cdot $ cm−2, and fill factor (FF) = 51.60) due to having enhanced conductivity/charge transfer efficiency by the hybrid semiconductor. This simple approach assures the low-cost mass production of heterojunction solar cells.

Green synthesis method is an effective approach for reduction of graphene oxide (GO) and the surface tuning of graphene nanosheets. In this work, facile green approach for the reduction of graphene oxide was adopted by utilizing phytochemical extracts of Citrus grandis (Pomelo) and Tamarindus indica (Tamarind). FTIR analysis showed significant reduction/elimination of the peaks that corresponds to the oxygen containing groups. XRD and Raman analysis confirmed the successful reduction of GO after treating with fruit extracts. The morphological analysis by SEM and TEM images further confirmed the formation of graphene nanosheets. The conductivity of both Pomelo-rGO (P-rGO) and Tamarind-rGO (T-rGO) were found to be 104-folds higher than that of GO. The electrochemical characterization of the synthesized rGO was done by cyclic voltammetry (CV). Specific capacitance of 65.25 F/g and 47.33 F/g were recorded for T-rGO and P-rGO, respectively. The results showed that this green synthesis route is promising for the large-scale production of rGO.

Electrochemical water splitting has brought clean route of green energy generation through its hydrogen evolution capability having no environment impact in the form of global warming. The related technology experiences challenges associated with cost, durability and mass production of hydrogen separated from water. Proper morphological design of highly active and low cost materials for both electrodes and electro-catalyst has become essential to deal with these issues. Here iron alloy cylindrical electrodes with screw pitched morphology and low cost ferrous hydroxide nano-particles have been introduced as an electrode and electro-catalyst respectively in compact integrated water electrolysis cell to catalyze both reactions in same electrolyte. Theoretical model of screw pitched electrode has been made to enhance sharp surface area for efficient Hydrogen and Oxygen evolution. It demonstrates water electrolysis using low cell voltage of 1.68 V at current density of 500 mA/cm2 with long term durability over 80 h having utilization efficiency of 73.88% and Faradaic efficiency of 80.714%. The experiments including high speed synthesis of nano-catalysts performed at room temperature provide guarantee of saving energy. This works promises a significant move towards mass production of hydrogen fuel through inexpensive method of water splitting.

This article presents a low-cost fabrication of binary/coupled ZnO–SnO2 composite semiconductors for heterojunction solar cells using a simple and effective sol-gel approach. Here, the synthesis and characterization of coupled ZnO–SnO2 nanocomposites are carried out with varied stoichiometry designated as ZnO–SnO2(20:80), ZnO–SnO2(50:50), and ZnO–SnO2(80:20). The X-ray diffraction (XRD) spectra confirmed an excellent crystalline domain in the order of ZnO–SnO2(80:20) > ZnO–SnO2(50:50) > ZnO–SnO2(20:80). Nanorods formation of ZnO–SnO2 has been confirmed through the scanning electron microscopy (SEM) micrograph. The improvement in photoconversion efficiency of solar cell from 3.39% to 3.98% was achieved due to increasing photo-excited free carrier generation with a significant change of nanorods dimensions. Furthermore, the UV–vis spectroscopy exhibited impressive transmittance of 85% in the wavelength range of 200–1000 nm. A bandgap modulation of 3.66–3.40 eV has been achieved. The power conversion efficiency (PCE) of 3.98 ( ${J}_{\text {sc}} = {18.83}$ mA/cm2, ${V}_{\text {oc}} = {0.581}$ V, and FF = 36.37) is determined using ZnO–SnO2(80:20), which is almost twice of that of a single semiconductor-based Al/ZnO/p-Si/Al solar cell.

Artificial photosynthesis based on solar guided water splitting is essential to obtain green renewable energy sources which is a potential replacement of fossil fuels. This paper presents a water splitting design with proper choice of non-precious and easily available composite metal (Fe, Ni, Mn and Al) based electrode to evolve the cleanest form of H2 and O2 separately through water electrolysis with a low voltage of 1.6 V using NaOH electrolyte of pH 12.7. The power supply embedded with solar panel connecting to the electrodes (anode/cathode) is maintained at a voltage level of 1.5–5 V in order to initiate the electrolysis process (electrolyte NaOH, pH = 12.7). This process leads to movement of H+ and OH− ions to cathode and anode kept within the gas chambers and the H2 gas evolved is stored. Experimental results show a high rate of H2 evolution that falls in the range of (7.3 × 1015 to 37.3x 1015) molecules s−1 and current density is found to be 2.6 mA cm−2 at 1.6 Volt which is far better than that of many state-of-the-art techniques. The proposed design setup along with the composite materials based electrode, produces a high rate of Hydrogen gas from H2O with high current density in low voltage.

This paper proposes a cost-effective sol–gel method for synthesis of ZnO nanostructure to make Al/ZnO/p-Si/Al heterojunction solar cell. Here, crystalline ZnO nanostructure was grown on p-silicon and annealed at 300 °C, 400 °C and 500 °C for application in heterojunction solar cell. The optimum temperature for obtaining uniform crystalline nanostructure was 500 °C, as confirmed from XRD and SEM imaging. As investigated by UV–Vis spectroscopy, the ZnO nanostructure layer exhibited high transmittance in the visible spectrum and has a direct band gap of 3.26–3.28 eV. The power conversion efficiency of Al/ZnO/p-Si/Al solar cell is enhanced from 1.06 to 2.22% due to increase in surface area of ZnO by formation of crystalline nanostructure due to increase of annealing temperature. The optimum value of short-circuit current (Isc) and open-circuit voltage (Voc) was measured using current–voltage (I–V) under AM 1.5 illuminations and found to be 9.97 mA and 460 mV, respectively.

An optical pulse controlled 2x2 two mode interference (OTMI) coupler having silicon core surrounded by Graphene clad has been introduced as fundamental gates of optical processing. Considering strong light –matter interactions and nonlinear optical property of graphene, we have shown coupling characteristics depending on additional phase change between the excited surface plasmon polariton modes propagating through the silicon core. By applying optical pulse energy of 0.82 pJ and width of 4 ps on graphene clad, the NOT, AND, and OR logic gates are demonstrated. The coupling length of the proposed device is ~ 3.2 times less than that of already reported optical device based on SPP modes. Our results promise to obtain the development of integrated of optical processor with high speed, compact and low power optical logic gates having high fabrication tolerance.

Polyaniline–graphene quantum dots (PANI–GQDs) are considered as an important candidate for applications in photovoltaic cells. In this work, GQDs were prepared using sono-Fenton reagent from reduced graphene oxide (rGO). PANI–GQD hybrid was also synthesized using the chemical in situ polymerization method. The synthesized materials were characterized using UV–visible (UV–Vis) spectroscopy, photoluminescence (PL) spectroscopy, current–voltage (I–V) characteristic, thermal gravimetric analysis (TGA), Raman spectroscopy, and X-ray diffraction (XRD). Dynamic light scattering was also used to estimate the lateral size of GQDs. The enhanced visible-light absorbance in the hybrid was confirmed by UV–Vis analysis and the decrease in intensity around 3461 cm−1 in FT-IR spectra was due to the interaction between functional groups of PANI with GQDs. This led to improved thermal stability and conductivity as observed from TGA and I–V analysis, respectively. Moreover, the Raman spectrum for PANI–GQDs showed a decrease in the peak at ~ 1348 and ~ 1572 cm−1 as compared to PANI and GQDs. Similarly, from the XRD profile of PANI–GQDs, a shift in peak was observed due to an alteration in the microstructure. A sandwich device with cell structure glass/ITO/PANI–GQDs/Al was fabricated and its application was tested. Current density–voltage (J–V) curve of the device was measured with a Keithley SMU 2400 unit under an illumination intensity of 100 Wm−2 simulating the AM 1.5 solar spectrum. The hybrid exhibited photovoltaic properties, and 0.857% efficiency was observed in response to the applied voltage. This work suggests that PANI can be used as an alternative material for photovoltaic cells.

Here, Graphene clad plasmonics waveguide is introduced as a two surface plasmonic polariton modes interference (GTSPPMI) coupler to obtain optically manipulated quantum interference. The manipulation of Handel Ou Handel (HOM) quantum interference is demonstrated theoretically in nano-scale two modes coupler through refractive index modulation in Graphene clad with incidence of an ultra fast optical pulse energy. The quantum entanglement of fidelity ~ 97.5% is obtained by incidence of optical pulse of energy 5.12 pJ and width 3.8 ps in Graphene cladding. Our results promise to obtain fast and compact optical reconfiguring of quantum plasmonics circuit in comparison to electrooptic and themooptic coupler.

ZnO nanostructures are promising for a wide range of applications, including gas sensors. Ethanol sensing using ZnO remains unexplored though. In this paper, we report ethanol-sensing using un-doped ZnO nano flowers and Mg doped ZnO nano flowers. These are grown using a rather simple chemo-thermal process, making this a plausibly scalable technology. To study the structural and morphological properties of undoped ZnO and Mg doped ZnO nanoflowers, Raman spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), x-ray diffraction and Field Emission Scanning Electron Microscopy (FESEM) are carried out. Ethanol sensing properties of undoped ZnO and Mg doped ZnO nanoflower devices are investigated toward different ethanol concentration (concentration range of 1–600 ppm at 100°C–200°C). Our findings show that 15% Mg doped ZnO nano flower is better than ZnO nano flower for ethanol gas-sensing applications.

Fish freshness plays a vital role in the fish industry and also affects human health from a nutrition point of view. Here, an Au metal patch electrode capacitive sensor is introduced for rapid and accurate detection of volatile gases generated from raw fish to determine its freshness status. The MIS structured sensor was fabricated on a silicon substrate using Ag–SnO2 as sensing material over SiO2 layer and Au as a metal electrode. The calibration of the sensor was carried out with known composition of volatile gases (NH3, TMA, DMA and H2S) in the ppb-ppm regime. Our sensor using the proposed technique delivers sensor response to raw fish within 4 min, reflecting its freshness status in comparison to the TVB-N and TVC method which takes many hours to complete involving many sophisticated steps. The sensor response to volatile gases from Rohu (Labeo Rohita), Tilapia (Oreochromis Niloticus) and Illish (Tenualosa Ilisha) obtained by using our developed sensor system at 20 °C, 25 °C, and 30 °C, shows high correlation with TVB-N and TVC results. The acceptance limit for safe consumption of Tilapia, Rohu, and Illish at 30 °C was found to be 11 h, 12.5 h, and 10 h of storage time respectively. The result in this work assures a portable low-cost sensor for onsite monitoring of fish freshness at room temperature.

In the paper, tooth structured grating-assisted (GA) configuration for 2 × 2 compact directional coupler (DC), two-mode interference (TMI) coupler and multimode interference (MMI) coupler have reported for an intensive study using a sinusoidal mode simple effective index method (SM-SEIM) centric mathematical model. It is found that beat length of GA-TMI coupler is ~22.3 µm which is almost 50% compact in size with comparison to the conventional TMI coupler and is ~25% that for conventional directional coupler. The power imbalance with grating-assisted structures increases as that of fabrication tolerances which are slightly higher compared to conventional TMI coupler.

The bulk heterostructure having nanopillar growth on top surface of the proposed photodetector structure is a promising candidate of high detection for high resolution quantum optic and high speed optical communication. Here, we report Si-ZnO-ZnMgO having grown with aligned hexagonal nanopillars for high performance photo detector, due to having its high quantum efficiency. From the proposed structure (electro-optically modified) high responsivity of $2.857\times 10^{2}$ AW $^{-1}$ and detectivity of $1.33\times 10^{15}$ cm Hz $^{1/2}\,\,\text{W}^{-1}$ (3mm $\times$ 3mm) was achieved and also the small performance degradation with increase of temperature shows thermal stability.

The remarkable development and continual proliferation of research in the nanotechnology field have led to improvement in the efficiency of elementary devices. To improve their performance, the parameters of such devices can be scaled down while optimizing their characteristics. However, this simultaneously results in degraded switching characteristics and the appearance of short-channel effects. Multigate-based fin-shaped field-effect transistors (FinFETs) represent a new option to address all these problems. However, thermal failure of FinFET devices under nominal operating conditions is an important issue in the design and implementation of high-speed semiconductor devices. It is also seen that bulk FinFETs exhibit better thermal performance compared with silicon-on-insulator FinFETs. In the work presented herein, various FinFET characteristics including the subthreshold swing, drain-induced barrier lowering, threshold voltage, and drain current were investigated as functions of temperature. The (effective) channel length is larger than the physical gate length (in off-state) due to the undoped underlap regions. This paper also discusses the effects of drain, source, and gate overlap.

High-performance photodiodes are desirable for ultrahigh speed optical communication and highresolution optical instrumentation. This paper reports both theoretical and experimental optimization approaches for low-cost chemothermal growth of hexagonal nanorods on Si-ZnO heterojunction. The alignments of nanorods were made by controlling the etching rate with the addition of 2% isopropyl alcohol during the process. The formation of nanorods were found to be linear, densely packed, and uniformly distributed on ZnO thin film as seen from SEM images and X-ray Diffraction (XRD) pattern. The X-ray Photoelectron Spectroscopy result shows the absence of carbon contamination and confirms the elemental composition of ZnO. The current–voltage measurement confirms ohmic junction between the nanostructure and ZnO thin film enhancing the increase of photocurrent, which provides high responsivity. The proposed fabrication process opens up the possibility of realization of low-cost, high-performance, and future flexible optoelectronics sensor circuitry.

A hydrothermal growth technique is introduced to synthesize hexagonal high sensitive zinc oxide (ZnO) with a large surface to volume ratio. Pre and post treatments are carried out to obtain suitable resistive performance, which enhanced sensing performance of the device. The morphological structure of synthesized ZnO under different conditions (such as reaction time solution concentrations) is characterized by scanning electron microscope (SEM). X ray diffraction (XRD) verifies the crystallinity in fabricated ZnO nanorod. X-ray photoelectron spectroscopy (XPS) is performed to measure the elemental composition corresponding to binding energy before and after treatment. Optical properties for as-grown sample and uniform ZnO nanorod are characterized through Photoluminescence (PL). Sensing properties depending on the shape, size, distribution of hexagonal nanorod, position of the IDE and temperature are investigated. The highest sensor response is achieved for the hexagonal nanorod which is uniform in shape, distribution and for the position of IDE below the sensing layer.

In this paper, a MIS based patch electrode multilayered capacitive sensor has been modelled mathematically. The sensor consists of ZnO sensing layer having patch top electrode, SiO2 layer and silicon substrate with bottom electrode. The overall capacitance of electrode is formulated by considering central, corner and fringe capacitances. The simulation was performed using mathematical mode to design the sensing layer thickness, patch electrode height and area and oxide layer thickness .

Graphene exhibits both surface plasmonics and non linear optical property. Considering these properties, an optical controlled compact graphene clad surface plasmonic polariton two modes interference (GCSPPTMI) structure with silicon waveguide core has been presented for all optical switching. The cross and bar state power of the device are obtained by introducing an additional phase between the excited SPP modes in silicon coupling region through nonlinear refractive index modulation of graphene clad with incidence of very low optical pulse energy of 0.82 pJ and width of 4 ps. The coupling length of the proposed device is ∼21.6 times less than that of existing all optical switch based on SPP modes. The degradation of power imbalances of the Graphene clad SPPTMI with fabrication tolerances (±) of both width and thickness is less than that of multimode interference based nonlinear directional coupler due to having less of device parameters. Our results promise to achieve high speed and compact optical switch.

We have introduced optically controlled two-stage cascaded surface plasmonic two-mode interference waveguide structure (having silicon core and silver upper and lower cladding) as universal gates. GaAsInP cladding is used in left and right side of core for optical pulse controlled cladding refractive index modulation which controls propagation of excited modes. The universal logic gate operations have been shown with this structure. These universal gates have potential in development of large-scale integrated optical processor due to its compactness and high fabrication tolerance.

In this paper, an optical controlled surface plasmonic two mode interference (SPTMI) structure based on silicon waveguide has been proposed for all optical switching. We have shown cross and bar state switching characteristics depending on additional phase between the excited SPP modes propagating through the silicon core obtained due to refractive index modulation of GaAsInP cladding with incidence of optical pulse of width ~1 ps. It is also seen that the coupling length of the proposed device is ~33 times compact than that of the existing multimode interference-directional coupler. The deviation of crosstalk of the SPTMI switch with increase of fabrication tolerances (±δw) is also almost to that of previously reported all optical switch.

Here, TiO2-reduced graphene oxide (rGO) has been reported as a very effective UV photodetection material. The TiO2-rGO composite samples with different ratios were prepared by using a green synthesis technique and an MSM photodetector was fabricated on SiO2-Silicon wafer. The XRD diffraction of TiO2-rGO composite reveals the presence of both anatase and rutile phase of TiO2, whereas Raman spectra of the sample indicate the increase of ID/IG ratio with the increase of rGO percentage. A high responsivity of 7.712 A/W, high detectivity of 7.92 × 1013 cm Hz.5W−1 with low response time of 43 ms were measured at UV illumination of 370 nm wavelength and power density of 10 μW/cm2 with TiO2-rGO composite device due to having slow recombination. A very low dark current of 7.3 nA of the device contributes to the reduced noise equivalent power. The low cost fabrication and high performance of the device assure wide commercial and military use.

An Au patch electrode Ag-SnO2/SiO2/Si MIS capacitive sensor equipped with a microcontroller was designed and developed to sense low concentration (ppb to ppm regime) of volatiles (NH3, TMA, ethanol, and H2S) generated from chicken meat spoilage at room temperature. The quality threshold or the acceptance limit for consumption of chicken meat samples stored at 4 °C, 15 °C and 25 °C using our proposed technique was found to be 105 h, 48 h, and 17 h respectively, highly correlated with TVB-N, TVC, pH and sensory evaluation analysis. When these well established standard methods (TVB-N, TVC and pH analysis) take many hours to complete the analysis involving many complicated steps, our fabricated sensor takes 55 sec to deliver sensing response reflecting the meat spoilage status. The sensor calibrated with our compact technique promises portable and inexpensive onsite rapid and accurate quality assessment of meat spoilage at room temperature.

In this paper, we have introduced a surface plasmonic two-mode interference (SPTMI) coupler having a silicon core, GaAsInP side cladding, and silver top and bottom cladding as an optical power splitter. A wide range of tunability from the 50∶50 splitting ratio to 1∶99 is achieved by refractive index modulation of the GaAsInP cladding with application of varying optical pulse power. The coupling length of the SPTMI-based splitter is ∼11.5 times less than that of a previously reported optical power splitter based on multimode waveguide holograms. The proposed optical power splitter has potential in development of large-scale integrated circuits due to its compactness and high fabrication tolerance.

Fill factor of the solar cell mainly depends on series resistance and contact resistance, which are the most effective parameters to collect carriers (electrons and holes) from both electrodes of C-Si solar cells. We have used both mathematical and experimental approaches to reduce these resistances for enhancement of power conversion efficiency (PCE) by increasing fill factor. After processing by light-induced plating (LIP) for metal contact, the PCE of solar cell is obtained as 14.43%, which is 8.8% more than that before LIP processing.

Overall series resistance of the contact increases due to unwanted pores created during the time of contact formation in solar cell. Light induced plating is an industrial established process which is used to reduce the series resistance and to improve the contact resistance resulting in increase of fill factor of solar cell through modification of front side contact. In this paper a theoretical modeling is done to show how distributed pores affect the series resistance and solar cell performance. Here we explored several parameters like: series resistance, shunt resistance, fill factor, short circuit current, and external quantum efficiency. Through our experimental setup it is found that the short circuit current improves significantly and also it is observed that during the time of experiment due to unintentional deposition of silver nanoparticles, external quantum efficiency improved by 5.249 % and a reduction of reflectance by 2.03 %. An overall enhancement of solar cell efficiency of 1.65 % is obtained during the process.

In this paper, we reported improvement in crystalline quality by changing structural properties of ZnO thin film into hexagonal shaped nanorods. ZnO thin films were deposited on Si (1 0 0) substrate using dielectric sputter. As-grown film (Sample A) was subjected to chemical etching for forming hexagonal nanorods. The overall electrical & optical performances like photo luminescence performance, X-ray diffraction performance in terms of crystal formation & reflectance performance are improver after rapid thermal & chemical treatments.

We have proposed a compact optical power splitter using two-mode interference (TMI) coupling in an index guided surface plasmonic waveguide. The device is made up of silicon core, silver upper and lower cladding and silicon dioxide side claddings. By using a numerical analysis based on effective index methods, the coupling characteristics of the device are studied and its application as a compact optical power splitter is shown theoretically for a wavelength of O.6328ILm. The device length for a 3dB power splitting ratio is estimated as 334 nm which is about rv313 times and ~1.31 times smaller than a previously published works.

Reduced graphene oxide (rGO) has been focused on different application such as photovoltaic, energy storage and clinical instrumentation due to its unique chemical, electrical and optical properties. Proper synthesis of rGO is required to achieve these properties. Here, a green approach using alcoholic mediums has been introduced to reduce the oxygen content in rGO for enhancement of electrical properties. The rGO samples prepared using ethanol, methanol, 2-propanol and acetone as reducing agents were analyzed by various characterization. The reduction of oxygen functional groups using ethanol medium promises a synthesis of rGO with enhanced electrical conductivity due to the presence of more graphene domain. The ethanol reduced graphene oxide provides band gap of 3.13 eV and room temperature conductivity of 1.19 S/m showing the semiconducting property for application of electronics device.

A 2x2 multimode interference structure with parabolic down tapering has been proposed and realized by using silica waveguides with silicon oxinitride (SiON) core for the reduction of coupling length. The coupling behavior and dependence of fabrication tolerances on power imbalance of the proposed tapered structure have been compared with those of other tapered MMI structures having both down and up tapering by using a mathematical model based on sinusoidal modes. It has been found both theoretically and experimentally that the beat length (Lπ) of the proposed tapered MMI coupler with Δn=5% is ∼ half that of conventional MMI coupler and the deviation of power imbalance from its minimum value with fabrication tolerances (± ∂w values) for the proposed tapered structure is more than that of other tapered structures.

In this paper we report on the design and fabrication of an Evanescent Optical Waveguide Sensor (EOWS) using silicon oxynitride (SiON) as the core layer on silica-silicon wafer and its implementation for rapid detection of adulterant traces in pure petrol incorporating composite planar waveguide geometry. The embedded waveguide of length ∼ 10,000 μm and core width ∼ 50 μm was fabricated using standard Plasma Enhanced Chemical Vapour Deposition (PECVD) technologies and Reactive Ion Etching (RIE) technique. The main aim of this work is to encompass an abrupt choice to the time-consuming existing adulteration detection methods which generally requires some time to give the consequence. Using Simple Effective Index Method (SEIM), the theoretical predictions and experimental results at wavelength 632.8 nm are analyzed and presented, which demonstrated that the sensitivity of the proposed EOWS is ∼40 times more than that of the existing planar waveguide sensors and also 20 times more than that of asymmetric waveguide structure thereby allowing rapid detection of adulterant traces in pure petrol without involving the use of chemicals. It is found that the sensor structure is polarization independent and advantages include high sensitivity, easy fabrication and more importantly, requirement of very minimal amount of sample volume for detecting adulteration.

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.

An ultra compact tooth shaped grating assisted structure has been studied using a mathematical model based on sinusoidal mode simple effective index method (SEIM) for compact two mode interference (TMI) couplers. The coupling characteristics with variation in number of grating period are also shown. It is seen that the beat length of tooth shaped grating assisted TMI coupler at Δn = 5% is 50% less than that of TMI coupler without grating. The wavelength dependence of power imbalance and the effect of fabrication tolerances on power imbalance are discussed.

A double S-bend lateral offset structure has been proposed for the reduction of length and S-bend loss of 2×2 two mode interference (TMI) coupler. The coupling characteristics of the proposed structure are compared with those of conventional TMI structures using a simple mathematical model based on sinusoidal modes. It is seen that the longitudinal beat length for the proposed TMI coupler is reduced by 15% of beat length of a conventional TMI coupler whereas the S-bending loss is reduced by ~ 50% by using lateral offset in the double S-bend structure. The effect of fabrication tolerance on power imbalance for the proposed TMI structure is also compared with other TMI structures. It is seen that the fabrication tolerance for the proposed structure with lateral offset is almost same as that without lateral offset.

An ultracompact optical-multiplexer-based two-mode interference (TMI) coupler has been designed for the first time using a mathematical model based on sinusoidal modes and implemented with silicon nano-waveguides. The multiplexing characteristics of the device are verified with the beam propagation method and are also demonstrated experimentally. The coupling length for the TMI coupler for multiplexing of wavelength channels of spacing ~10 nm is five times less than that of a conventional multimode interference (MMI) coupler of width 660 nm. The effect of fabrication tolerance on crosstalk of the TMI coupler is found to be less than that of conventional MMI couplers and of TMI coupler based on tooth-shaped grating structure.

A compact surface plasmonic two mode interference waveguide component having silicon core and silver and GaAsInP side cladding is proposed for optical processor elements. Coupling operation is obtained by using index modulation of GaAsInP cladding with applied optical pulse.

Thermal analysis of thermooptic device using planar optical waveguide structures is performed by using implicit finite difference method. Isothermal profiles of the medium having the core and cladding are shown from the computation results. We have proposed two new structures where lower heating power is required when compared to that of the conventional structure. A compromise between heating power and response time is made for different applications of thermooptic devices.

A new tapered structure based on general interference has been proposed and realized by using silica waveguides with a silicon oxinitride (SiON) core for the reduction of coupling length of the 2times2 multimode interference (MMI) coupler. The coupling characteristics of the proposed structure are compared with those of conventional MMI structures using a simple mathematical model based on sinusoidal modes. The beat length for the proposed tapered MMI coupler is reduced by 45% of that of a conventional MMI coupler. The effect of power imbalance on fabrication tolerance of the proposed tapered MMI coupler are also studied and compared with other tapered MMI couplers.

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.

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.

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.

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.

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.

We propose to use ZnO thin film with hexagonal nanopillars deposited on Si substrate to enhance the efficiency of a solar cell. It has been treated chemically and thermally and various crystal orientations have been obtained. X-ray diffraction of ZnO thin film shows relatively high intensity peak at 34.3° angle (0 0 2) compared to other orientations. Photoluminescence measurements also confirm a narrow full width at half maximum peak at 3.3 eV, which is more than that obtained for as-grown (broad emission peak around 3.0 eV). The alignment of nanorod structure made by adding a dopant of 0.15 mole fraction of magnesium increases both photon collection and electron collection efficiency. As a result, the solar cell efficiency is enhanced from 10% to 20%.

A thermo-optic two-mode interference (TMI) waveguide structure with a silicon trench and heat-insulating grooves in both sides of the core has been proposed for a variable optical attenuator (VOA) with fast response time. Thermal analysis of the proposed thermo-optic TMI waveguide structure with a silicon oxinitride (SiON) core has been performed by using the implicit finite difference method. The heating power required to achieve the attenuated power of approximately -25.5 dB for a VOA with a silicon trench is 460 mW , which is approximately 1.8 times less than that of a VOA without a silicon trench. The response time is estimated as approximately 98 micros, which is faster than the response time of the existing VOA.