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About this book

This book highlights recent advances in thin-film photonics, particularly as building blocks of metamaterials and metasurfaces. Recent advances in nanophotonics has demonstrated remarkable control over the electromagnetic field by tailoring the optical properties of materials at the subwavelength scale which results in the emergence of metamaterials and metasurfaces. However, most of the proposed platforms require intense lithography which makes them of minor practical relevance. Stacked ultrathin-films of dielectrics, semi-conductors, and metals are introduced as an alternative platform that perform unique or similar functionalities. This book discusses the new era of thin film photonics and its potential applications in perfect and selective light absorption, structural coloring, biosensing, enhanced spontaneous emission, reconfigurable photonic devices and super lensing.​

Table of Contents

Frontmatter

Development and Applications of Metal/Dielectric Resonant Cavity-Based Thin Film Structures

Frontmatter

Chapter 1. Perfect Light Absorption in Thin and Ultra-Thin Films and Its Applications

Abstract
Perfect light absorption (PLA) has a wide range of applications from solar-thermal based applications to radiative cooling. In this chapter, we discuss the main schemes to realize PLA using thin-film nanocavities. We cover some of the main applications of thin-film based PLA.
Sreekanth K. V., Mohamed ElKabbash, Vincenzo Caligiuri, Ranjan Singh, Antonio De Luca, Giuseppe Strangi

Chapter 2. Realization of Point-of-Darkness and Extreme Phase Singularity in Nanophotonic Cavities

Abstract
The Aharonov–Bohm effect [1] and the Berry phase [2] are the two important physical phenomena that depends on non-trivial behavior of phase. In particular, singular photonics relies on the abrupt phase changes. The maximum phase change occurs at the point-of-darkness where the incident light is completely absorbed. This phenomenon has been widely investigated using different material systems through the concept of topological darkness [3]. However, to realize topological darkness, sub-wavelength nanostructures are required which demand intense nanofabrication steps. In this chapter, we demonstrate a new approach to realize point-of-darkness and extreme phase singularity using lithography-free metal-dielectric multilayer thin film stacks. We further demonstrate the potential applications of this concept in ultra-sensitive label-free biosensing.
Sreekanth K. V., Mohamed ElKabbash, Vincenzo Caligiuri, Ranjan Singh, Antonio De Luca, Giuseppe Strangi

Chapter 3. Phase Change Material-Based Nanophotonic Cavities for Reconfigurable Photonic Device Applications

Abstract
The discovery of the interesting optical properties of phase change materials (PCM) may open the door for photonic data storage again. These materials modify their optical constants which can be rapidly activated thermally, optically, or electronically. In this chapter, we discuss the optical properties of phase change material such as Sb2S3 and Ge2Sb2Te5 for visible and near infrared (NIR) photonics applications. In particular, we demonstrate PCM-based planar nanophotonic cavities for realizing tunable color filters, tunable wide-angle perfect absorption and tunable phase singularity, and Goos-Hänchen shift.
Sreekanth K. V., Mohamed ElKabbash, Vincenzo Caligiuri, Ranjan Singh, Antonio De Luca, Giuseppe Strangi

Chapter 4. Sub-wavelength Nanopatterning Using Thin Metal Films

Abstract
Over the decade, photolithography has played a vital role in almost every aspects of modern technology. Developments in this field have allowed researchers to improve the resolution of the conventional photolithographic techniques that is restricted by the optical diffraction limit [1]. However, the implementation of recently developed high resolution lithography techniques beyond the diffraction limit are challenging because of their significant design and layout issues. In this chapter, single-exposure multiple-beams interference lithography generated by thin metal films are demonstrated, which overcome the issues associated with the optical diffraction limit.
Sreekanth K. V., Mohamed ElKabbash, Vincenzo Caligiuri, Ranjan Singh, Antonio De Luca, Giuseppe Strangi

Development and Applications of Multilayered Hyperbolic Metamaterials

Frontmatter

Chapter 5. Dielectric Singularities in Hyperbolic Metamaterials

Abstract
In this chapter, a special propagation regime is described, occurring in particular HMMs with extreme parameters. These HMMs are designed to manifest a vanishing effective permittivity in the direction parallel to their surface plane while an ideally infinite one in the perpendicular direction. Such a unique feature allows the HMM to behave as a perfect near-field lens.
Sreekanth K. V., Mohamed ElKabbash, Vincenzo Caligiuri, Ranjan Singh, Antonio De Luca, Giuseppe Strangi

Chapter 6. Resonant Gain Singularities in Hyperbolic Metamaterials

Abstract
The interaction between dyes and plasmonic metals has been widely studied in numerous frameworks. In the previous chapter, a new propagation regime has been introduced in which a suitably dimensioned HMM can collimate light with unprecedented resolution. It has been explained that such a regime, called Epsilon-near-zero-and-pole (ENZP), is characterized by high losses in the visible. In this chapter, it will be shown how to compensate losses in the ENZP regime by means of a particular fluorescent blend designed appositely.
Sreekanth K. V., Mohamed ElKabbash, Vincenzo Caligiuri, Ranjan Singh, Antonio De Luca, Giuseppe Strangi

Chapter 7. Metal/Photoemissive-Blend Hyperbolic Metamaterials for Controlling the Topological Transition

Abstract
In this chapter, we present a simple method to overcome the intrinsic lack of tunability and reconfigurability manifested by HMMs. The proposed method bases on the engineering of a hygroscopic dielectric material consisting in a TiO2/Polymer/Dye blend, providing a thermally tunable response in the visible range. Each of the blend components plays a fundamental role in the design of the optical, environmental and photophysical response of the complete HMM. The presence of the dye within the dielectric matrix allows a visual detection of the thermal reconfiguration, permitting the proposed architecture to be considered as the proof-of-concept for the future engineering of a temperature sensor device working in a humidity-controlled environment, or vice versa, as a humidity sensor at a fixed temperature, both based on the proposed phenomenon.
Sreekanth K. V., Mohamed ElKabbash, Vincenzo Caligiuri, Ranjan Singh, Antonio De Luca, Giuseppe Strangi

Chapter 8. Guided Modes of Hyperbolic Metamaterial and Their Applications

Abstract
HMMs support highly confined non-radiative modes such as high-k modes, in addition to surface plasmon modes within the structure due to hyperbolic dispersion. It is a challenging task to excite and collect BPP modes especially at optical frequencies, since they are highly confined within the HMM. In this chapter, we focus on the excitation and collection of BPP modes of multilayered HMMs in the optical frequencies, using grating and prism coupling techniques. We further demonstrate that the proposed grating and prism coupled HMMs exhibit an extraordinary potential to open new routes towards a wide range of breakthrough applications such as biosensing, spontaneous emission enhancement, multiband perfect absorption and reconfigurable photonic devices.
Sreekanth K. V., Mohamed ElKabbash, Vincenzo Caligiuri, Ranjan Singh, Antonio De Luca, Giuseppe Strangi

Chapter 9. Graphene and Topological Insulator-Based Active THz Hyperbolic Metamaterials

Abstract
In this chapter, we demonstrate negative group refraction properties of graphene- and topological insulator-based HMMs. Graphene-based HMMs show type II hyperbolic dispersion and topological insulator such as Bi2Se3 shows both type I and type II hyperbolic dispersion at terahertz (THz) frequencies. In type II spectral region, negative group index of refraction at higher angles of incidence is obtained for both HMMs. However, an all angle negative group index of refraction is observed in the type I hyperbolic dispersion of Bi2Se3. Moreover, we demonstrate broadband tunable hyperbolic dispersion from THz to mid infrared frequencies and a widening of the negative group index spectral band using topological insulator-dielectric insulator based superlattice structures.
Sreekanth K. V., Mohamed ElKabbash, Vincenzo Caligiuri, Ranjan Singh, Antonio De Luca, Giuseppe Strangi
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