Photonic crystals (hereafter represented as PCs), a synthetic dielectric formation that employs periodic and random changes in the refractive index to control the transmission of light, were presented by Yablonovitch and John in 1987. The capability to change the transmission of the electromagnetic wave in these formations on a miniature scale is used by photonic devices built on PCs. Electromagnetic waves scatter within the PC, and destructive intrusion happens at particular wavelengths, resulting in a photonic bandgap like the energy bandgap of electron waves in a semiconductor (hereafter denoted as SC). Because of the possibility of constructing a photonic bandgap, it may be feasible to influence light transmission. Instruments with tiny footprints are also feasible. In recent years, several fascinating PC-based devices, such as sharp bent waveguides (henceforth denoted as W/G), μ-resonator cavities, and Y-branches, have been demonstrated. These remarkable properties have the potential to result in the growth of a dense integrated circuit. Though PC technology is still in its infancy, and more study is needed in this field, this chapter summarizes recent developments in this sector by presenting the utmost frequent and necessary optical devices established on PCs such as optical logic gates, optical power splitters, polarization splitters, sensing devices, and lasers. In comparison to conventional photonic devices, these devices have greater efficiency and a small footprint.

Most major high-speed applications, such as communications, environmental monitoring, transportation, smart homes, industries and gadgets are enabled by recent photonic technology. Basic all-optical logic gates are used in the development of image sensors, ultra-fast optical devices, and positioning equipment in high-speed applications. Among different technologies proposed for all-optical implementation, Semiconductor Optical Amplifiers (SOA) have been widely adopted. They have attractive features such as wide gain bandwidth, low power consumption, compactness and strong non-linearity. SOA still has a limitation that its spontaneous emission noise restricts the performance. The semiconductor optical amplifiers with quantum dots exhibit higher saturation output power, lower current density threshold, wider gain bandwidth, and low noise figure than conventional SOA. Quantum Dot Semiconductor Optical Amplifiers (QDSOAs) also have limitations like large size, high power consumption and spontaneous emission of noise. Photonic Crystal (PhC) is an artificial material that is suitable to overcome all drawbacks of SOA and QDSOA due to its simple structure and compactness, high speed, low power consumption, and low loss. PhC-based structures allow propagation of light in a controlled manner with its periodic crystal arrangements having dissimilar diffraction index. PhCs are considered to be a suitable structure for designing all-optical devices with compactness. In this chapter, an all-optical XOR is designed. Initially, the XOR gate is designed and simulated by using the FDTD method. The proposed XOR logic is achieved without nano-resonators and then with nanoresonators to get enhanced performance metrics in the form of high contrast ratio. The contrast ratio is 260 dB for the XOR gate with a delay time of 0.19 ps. The proposed XOR logic gate has potential practical applications for high speed applications of telecommunication systems.

In this work, we theoretically investigate and study the effect of hydrostatic pressure on the reflectance and transmittance properties of the one-dimensional PC (1D PC) containing germanium (Ge). In the present study, we first take a 1D PC structure composed of alternate layers of germanium (Ge) and air having a finite number of layers. In the second case, we take the same structure by breaking its periodicity such that each part of it acts as the mirror image of each other. The Refractive index of germanium varies under the applied pressure, therefore both reflection bands and transmission modes change with the applied pressure. In order to calculate transmittance and reflectance spectra of the proposed PC, the transfer matrix method (TMM) has been used. It has been observed that by increasing the hydrostatic pressure, the width of the reflection band decreases and the position of reflection bands shifts towards the lower side of wavelength. Further, the transmission modes of the considered PC structure are blue shifted with the increase in applied hydrostatic pressure and show high sensitivity with it. 

Plasmonics is an emerging and fast-growing branch of science and technology that focuses on the coupling of light to the free electron density in metals, resulting in strong electromagnetic field enhancement due to confinement of light into sub-wavelength dimensions beyond the diffraction limit. The development of novel photonic and optoelectronic devices based on metal-based plasmonics is however plagued by the high loss at optical frequencies, originating partly from inter-band electronic transitions and lack of electrical tunability, practically limiting their potential applications in the terahertz (THz) and mid-IR spectrum range. The recent successful exfoliation of graphene from graphite has rendered a breakthrough in the realm of plasmonics due to its phenomenal properties such as exceptionally tight light confinement, extremely long plasmon lifetime, high carrier mobility leading to a relatively low level of losses, strong optical nonlinearity and electrostatically as well as chemically tunable response. These versatile features of graphene can effectively address the challenges faced by metals, and hence the physics and potential applications of graphene-based plasmonics have triggered increasing attention of industry, academic and research fraternity in recent years. This chapter provides a comprehensive description of the theoretical approaches adopted to investigate the dispersion relation of graphene surface plasmons, types of graphene surface plasmons and their interactions with photons, phonons and electrons, experimental techniques to detect surface plasmons, the behaviour of surface plasmons in graphene nanostructures and the recent applications of graphene-based plasmonics.

 Energy is the basic input for the improvement of the social status of human beings and the development of a nation. At present, we are observing a shift in the use of energy from non-renewable to the renewable energy due to exhausting natural resources of non-renewable energy and other environmental and climatic concerns. Solar energy resource is an inexhaustible source of energy. The development of first generation solar cells using silicon material in the middle of the nineteenth century introduced a new era in the renewable energy transformation process when the first solar cells were flown on the fourth satellite, the Vanguard-I in 1958. But despite abundant material resources, high stability and good performance, this technology could not fulfill the energy need except a fraction due to very long payback time. The second generation solar cells are also not very encouraging due to the scarcity of materials and their toxic nature. The third generation solar cells, due to extremely low energy payback time and unlimited availability of material are promising devices to contribute significantly in solar energy conversion, despite limitations of poor stability and low efficiency. The present chapter critically analyses the third generation solar cells, in regard to materials, production, fabrication process, energy payback time, efficiency and applications.

There has been incredible progress so far in graphene (Gr)-based solar cells and this is going to continue well into the future. Therefore, it is important to get an idea of the recent progress of graphene-based solar cells in the last decades. In this chapter, a brief overview of the recent research on Gr in solar cell applications has been outlined. It is prominent that Gr has been used in heterojunction solar cells, GaAs solar cells, Dye-sensitized Solar cells (DSSC), Perovskite solar cells, Polymer solar cells, and organic solar cells. In these solar cells, Gr has been utilized either as an absorber layer, hole transport layer, or electron transport layer. However, Gr has been used in the form of thin film, flakes, or quantum dot form. About 25% output efficiency has been observed in Gr-based solar cells so far. This chapter gives an overview of the Grbased solar cell with efficiencies to further continue the research on Gr-based solar cells to achieve higher efficiency.

Recent developments in nanotechnology have resulted in significant technical improvements in devices based on light's interaction with nanomaterials. As a result, nanophotonics has seen a significant increase in attention among researchers. The significance of low energy consuming information processing at high rates of speed has pushed the use of light for information transmission and processing forward. Nanophotonics hence introduces ways of integrating a wide range of systems that can produce, regulate, amplify and process light waves that are at superfast accelerations, as energy demands and interaction time decrease with a decrease in the particle dimensions of the nanomaterials. Nanophotonics, also known as nano-optics, is a branch of nanotechnology that studies characteristics of light at nanoscale dimensions and the interrelationships of nano-scale materials with light. Nanophotonics is a subfield of nanotechnology and a discipline of optoelectronics. On a dimension considerably smaller than the wavelength of light, it presents new opportunities for exploring concepts of interaction between the propagating light and matter. Fundamental properties of nanomaterial-light interactions, such as nanometer photon confinement and change in optical, chemical and physical properties of the material in nanorange, continue to provide numerous possibilities for real-life applications. The optical characteristics of materials can hence be enhanced by these materials having dimensions smaller than the wavelength of light. Electromagnetic waves are diffracted and dispersed if the material has dimensions in the range of the light wavelength or a portion of the wavelength, and the numerous waves produced interfere with each other. Controlling the spatial distribution of light, as well as its phase, polarization, and spectral distribution may be accomplished by understanding such materials. Moreover, materials with lower dimensions can be used to make extremely condensed sophisticated systems in a variety of industries, including information technology, optical interactions, photovoltaic energy, image processing, medical and surveillance. This chapter reviews the various materials used for nanophotonics and their properties as well as their nanophotonics application.

As the world is modernizing, it is noteworthy to mention photonics and its categorization based on size. Despite the components of light being invisible to the human eye, nature never ceases to amaze us with its idiosyncratic phenomenon. Furthermore, the manipulation of the matter is confined to the nanoscale as a part of the progression. Adding nanotechnology to photonics emerges out as nanophotonics which is the cutting-edge tech of the twenty-first century. Human beings have acclimated to the concept of photonics, furthermore, nanophotonics is the science of miniaturization study, potentially helping the technology to modify itself into the sophistication of the equipment and thereby be of assistance in various disciplines of science and technology. One can illustrate nanophotonics by considering the fabrication processes of nanomaterials. In variegated applications, these nanoscale processes will refine and produce structures with high precision and accuracy. Meanwhile, groundbreaking inventions and discoveries have been going around, from communications to data processing, from detecting diseases to treating diseases at the outset. As one stresses on the idea of nanophotonics, it never reaches a dead-end, however, this explains how vast the universe and each of the components co-existing are infinitesimally beyond humans' reach. Nevertheless, nanophotonics and its applications bring about remarkable multidisciplinary challenges which require proficient and well-cultivated researchers. Despite the fact it has several advantages, it carries its downside, which requires a detailed analysis of any matter. Using state-of-the-art technology, one can constrict light into a nanometer scale using different principle methodologies such as surface plasmons, metal optics, near field optics, and metamaterials. The distinctive optical properties of nanophotonics call out specific applications in the electronics field such as interaction chips, tiny devices, transistor filaments, etc. When compared to conventional electronic integrated circuits, the pace at which data using nanophotonic devices is sent is exceptionally fast, accurate, and has a better signal processing capability. As a result of the integration of nanotechnology with photonic circuit technology, high-speed data processing with an average processing speed on the order of terabits per second is possible. Furthermore, nano-integrated photonics technology is capable of comprehensive data storage and processing, which inevitably lays the groundwork for the fabrication, quantification, control, and functional requirements of novel optical science and technology. The maj-ority of applications include nanolithography, near-field scanning optical microscopy, nanotube nanomotors, and others. This explains about the working principle, different materials utilized, and several other applications for a better understanding.

The paramount goal of this fundamental explanatory book chapter has been to investigate a simulative study on EO (Electro-Optic) characteristics of InAlGAs/InP heterogeneous nanostructure for GFOCs (Graded Fiber Optic Cables) based SIL (Shortwave Infrared Light) communication systems under several numbers of NWTLs (Nanoscale Well Thickness Layers) in the photonic material based emerging nanotechnological sciences. The energy values in eV of C-V (Conduction-Valence) band offsets with SN (Step Normalized) width and the maximum value of quasi-Fermi energies in eV with various NWTLs have been illustrated graphically under the exploratory simulation in this chapter. Under this simulative investigation, the computational performances of SIL gain amplification with photon’s wavelength and values of carrier concentration per unit volume for several NWTLs have been properly calculated. Next, other various critical parameters such as modal confinement SIL gain amplification and A-G (Anti-Guiding) parameter with values of current per unit area of the cross-section for various values of NWTLs have been calculated cumulatively. Moreover, the performances of differential SIL gain amplification with carrier densities per cubic cm for various NWTLs have been illustrated. It has been distinguished by SIL gain spectra that the peaks of SIL gain spectra are enhanced with a decrease in the value of NWTLs and have been shifted towards the low value of the wavelength of lasing due to enhancement in energy separation values between quasi-Fermi energy levels. In the exploratory investigation through the results, the crest values of SIL gain amplification are ~ 6100/cm and ~ 5100/cm at the photon wavelengths ~ 1332 nm and 1553 nm respectively for 4 nm and 6 nm values of NWTLs. The SIL of maximum intensity emitted by the proposed heterogeneous junction based nanostructure of wavelengths ~ 1332 nm and 1553 nm has been largely utilized in the GFOCs-based SIL communication systems through the process of TIRs (Total Internal Reflections) with no attenuation loss of SIL signals in dB/km because of diminished net dispersions, scattering and net absorptions in the photonic material.

Two-dimensional (2D) materials such as graphene, chalcogenides, topological insulators, black phosphorus, and MXenes have of late become the focus of intense research efforts due to the excellent and unique optoelectrical properties these materials possess. This is due to the unique properties these materials possess, such as tunable bandgaps, high mobility in the energy bandgap, third-order nonlinearity, and nonlinear absorption that can be tailored to suit the specific needs of different optical applications. These properties have allowed for the development of fiber optic-based pulsed laser systems with better integration and flexibility capabilities as well as improved performance as compared to their bulk counterparts. In this chapter, the development of optical fiber pulsed lasers that incorporate selected 2D materials, particularly 2D chalcogenides that encompass metal monochalcogenides (MMs), and traditional metal dichalcogenides (TMDs) and MXenes is reviewed. This chapter will cover the fundamental aspects of the aforementioned materials, the operating principles of Q-switching and mode-locking, and the configuration of these 2D materials as saturable absorbers (SAs). The main section of this chapter will focus on the current status of the development of Q-switched and mode-locked optical fiber laser systems using 2D material-based SAs. Finally, the chapter will explore the perspectives and challenges on the future of the potential applications of these 2D materials in pulsed optical systems.

The propagation and dispersion properties of hollow-core Bragg fibre waveguides for both high and low refractive index contrasts of cladding materials are explored and compared in this chapter using two design wavelengths: 1550 nm in the near-infrared area and 632.8nm in the visible range. The boundary matching approach was used to build a relationship between the incoming and outgoing light waves employing the transfer matrix method. The observed photonic band gaps are somewhat substantial in high refractive index contrast cladding Bragg fibre waveguides, i.e. HRBFW, and low periodic cladding layers are required to achieve a perfect photonic bandgap. The spectrum range and spectral location of photonic band gaps in both HRBFW and low refractive index contrast cladding Bragg fibre waveguides, i.e. LRBFW, are substantially dependent on the angle of incidence of a light beam, i.e. the optical path of the incident light. The sensitivity of the Bragg fibre waveguide for sensing applications may be determined by measuring the thickness of the photonic bandgap or the spectral shift of the photonic bandgap. HRBFW seems to have a high sensitivity when considering the change in spectral bandwidth of photonic bandgap with core refractive index, which grows with increasing design wavelength. LRBFW has a much higher sensitivity than HRBFW when considering the LBE (Left band edge) and RBE (Right band edge), hence it is suggested for sensing applications. HRBFW directed a greater number of modes than LRBFW, according to the assessment of dispersion characteristics.

The adulteration of liquid fuels has several far-reaching repercussions, including pollution and a rising energy crisis. Around the world, fossil fuels are widely utilized for transportation and energy generation. Fuel adulteration currently threatens a big number of customers. Adulteration of fossil fuels with other recognised hydrocarbons is a common occurrence. Adulterants are added to these base fuels in the form of additional low-cost hydrocarbons with similar compositions, leading the base to be altered and degraded. Adulteration is an unauthorised or illegal introduction of a lower-quality external substance into a higher-quality commodity, causing the latter to lose its original composition and qualities. The Opto-Microfluidics approach is a new field that uses a small sample to identify adulteration in food and fuel, resulting in high-resolution findings. Consumers will benefit from very sensitive detection of dangerous adulteration in any commodity thanks to opto-microfluidic lab-on-chip technologies. Using the metal-polymer nanocomposites’ multilayer cylindrical nanostructure with a microfluidic channel, we develop a real-time and temperaturedependent prototype of the Bragg Opto-microfluidic sensor for effective tracking of contaminated fossil fuels. The purpose of this chapter is to examine the biological motivations for the development of multilayer photonic nanostructures and various types of fuel adulteration detection optical sensors using various sensor-based techniques, as well as to compare the Bragg Metal-Polymer nanocomposites optical sensor with other optical sensors. This chapter is devoted entirely to the use of the theoretical model's Kay, Eykman, Dale-Gladstone, Newton, and Lorentz-Lorenz, as well as Hankel formalism and the transfer matrix method for cylindrical symmetry.

Silicon photonics allows for high yield and complex integration with large processing, packaging, and testing availability. Using silicon as a material leverages the use of the existing CMOS infrastructure with hybrid and epitaxial layer integration, allowing photonic system-on-chip. Although high refractive index contrast with submicrometer waveguide dimensions allows a dense integration, sensitivity to fabrication variations shows an increased effect. This sensitivity shows a cumulative effect on the optical properties of complex silicon photonic circuits such as lattice filters, and wavelength division multiplexers (WDM). This increases the demand for model fabrication variation at the design stage itself since the fabless users have no insights into the process specifications. As a result, reliability modelling of photonic circuits has shown significant interest in recent years. This is done by using efficient behavioural models at the circuit level and then applying random variations in the model parameters to assess the impact of these variations. In this chapter, different approaches to modelling fabrication variations in photonic integrated circuits, such as Monte Carlo (MC), Stochastic Collocation (SC), and Polynomial Chaos Expansion (PCE) are reviewed. These methods employ random distribution to the varying parameters with the correlation between different parameter sets fixed. Virtual Wafer-based MC (VWMC) allows layout-aware variability analysis, where the placement of circuit components on the layout coordinates is exported to the circuit design for dependence analysis. Using these methods, mitigation strategies to counter the manufacturing variations such as thermal compensation, and tapered designs are quantitatively evaluated by appropriate yield analysis and design for manufacturability.

Smart materials are the name given to materials that can alter their properties on the application of external stimuli. Devices using smart materials might replace more conventional technologies in a variety of fields. Smart materials are attractive due to their lightweight, sensing capability, lower component size, and complexity combined with design flexibility, functionality, and reliability. A smart material is an object which is susceptible to undergoing a material property change and shows a visual and tangible reaction to external stimuli. Proper execution of smart materials will provide a level of environmental robustness that is not easily achieved through conventional technologies as they are susceptible to the influences of nature. One concept which includes the futuristic application of smart materials is the utilization of smart materials in the transportation sector using shape-memory alloys and piezoelectricity. Although the applications of smart materials are far-reaching, a greater dependency on them is prevented by certain drawbacks that need to be addressed if utilization of smart materials is to be accomplished, such as system compatibility, availability, cost, delicateness, decreased performance over time, difficulties with integration and toxicity.