Thesis advisor: Michael J. Naughton / For many centuries, physicists and engineers have explored the creation, manipulation and detection of light. Only within the past century, however, have fabrication techniques advanced to the point where individual photons can be generated, manipulated, and measured. These advances have brought us to the point we are at today, where photonic devices are set to revolutionize the fields of computing, sensing and quantum information, to name a few. Despite the promise of these devices, scientists are still working to fully understand the light-matter interactions that govern their behavior. In this thesis, we uniquely characterize the behavior of certain photonic devices in an effort to understand the underlying physical principles that define them. Of particular interest to us is imaging via near-field scanning optical microscopy (NSOM) of photonic integrated circuit (PIC) elements with high quality factors (Q), such as microring resonators and photonic crystal cavities (PhCs). While these elements are becoming ubiquitous in emerging PIC designs, they have remained difficult to accurately image due to their high sensitivity to small perturbations (i.e. the NSOM probe). We solve this problem by controllably modulating the NSOM tip-sample distance and reducing the size of the probe. Finite element model computer simulations demonstrate that both of these adjustments decrease the tip sample interaction. We then apply this knowledge to generate first of their kind 50 nm resolution NSOM images of high Q resonant PIC devices. Importantly, aside from being accurate, the proposed NSOM technique is also facile and non-destructive. In addition to local field exploration of PIC elements, we explore non-classical optical transmission through sub-wavelength apertures in metallic films. We demonstrate that these interesting features arise from photonic wave interference. / Thesis (PhD) — Boston College, 2024. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Physics.

Near-field optical microscopy has attracted remarkable attention, as it is the only technique that allows the investigation of local optical properties with a resolution far below the diffraction limit. Especially, the scattering-type near-field optical microscopy allows the nondestructive examination of surfaces without restrictions to the applicable wavelengths. However, its usability is limited by the availability of appropriate light sources. In the context of this work, this limit was overcome by the development of a scattering-type near-field microscope that uses a widely tunable free-electron laser as primary light source. In the theoretical part, it is shown that an optical near-field contrast can be expected when materials with different dielectric functions are combined. It is derived that these differences yield different scattering cross-sections for the coupled system of the probe and the sample. Those cross-sections define the strength of the near-field signal that can be measured for different materials. Hence, an optical contrast can be expected, when different scattering cross-sections are probed. This principle also applies to vertically stacked or even buried materials, as shown in this thesis experimentally for two sample systems. In the first example, the different dielectric functions were obtained by locally changing the carrier concentration in silicon by the implantation of boron. It is shown that the concentration of free charge-carriers can be deduced from the near-field contrast between implanted and pure silicon. For this purpose, two different experimental approaches were used, a non-interferometric one by using variable wavelengths and an interferometric one with a fixed wavelength. As those techniques yield complementary information, they can be used to quantitatively determine the effective carrier concentration. Both approaches yield consistent results for the carrier concentration, which excellently agrees with predictions from literature. While the structures of the first system were in the micrometer regime, the capability to probe buried nanostructures is demonstrated at a sample of indium arsenide quantum dots. Those dots are covered by a thick layer of gallium arsenide. For the first time ever, it is shown experimentally that transitions between electron states in single quantum dots can be investigated by near-field microscopy. By monitoring the near-field response of these quantum dots while scanning the wavelength of the incident light beam, it was possible to obtain characteristic near-field signatures of single dots. Near-field contrasts up to 30 % could be measured for resonant excitation of electrons in the conduction band of the indium arsenide dots.

This thesis proposed a near-field electromagnetic interference measurement framework to obtain sensitivity and spatial resolution of the characteristic parameters of magnetic probe based on International Electrotechnical Commission proposed for integrated circuits electromagnetic radiation measurement standards IEC 61967-6 : magnetic probe method. Using cross-coupled planar microwave bandpass filter which is realized by glass fiber board (FR4) for near-field measurement and electromagnetic simulation in comparsion. Nowadays, integrated circuits has become an important source of energy of overall electromagnetic interference in electronic systems. Finally, do near-field scanning measurement for a 64-pin wire-bond quad flat nonlead (WB-QFN) package and the voltage-controlled oscillator chip in 0.18 £gm CMOS technology by using high scanning resolution of microprobe. Then observes the chip-level and package-level electromagnetic interference, and achieve chip-level of near-field electromagnetic interference measurement techniques.

The light-matter interaction in the near-field of high-Q resonators in SOI and SiN platforms is studied. The interactions of high-Q traveling-wave resonators with both resonant and non-resonant nanoparticles are studied and different applications based on this enhanced interactions in near-field such as high-resolution imaging of mode profile of high-Q resonators, label-free sensing, optical trapping, and SERS sensing are investigated. A near-field imaging system for the investigation of the near-field phenomena in the near-field of high-Q resonators is realized. A new technique for high-resolution imaging of the optical modes in high-Q resonators based on the near-field perturbation is developed that enables to achieve a very high resolution (< 10 nm) near-field image. The prospect of the high Q resonators on SOI platform for highly multiplexed label-free sensing and the effect of different phenomena such as the analyte drift and diffusion and the binding kinetics are studied. Also, the possibility of enhancing nanoparticle binding to the sensor surface using optical trapping is investigated and the dynamic of a nanoparticle in the high-Q resonator optical trap is studied. Furthermore, the interaction between a resonant nanoparticle with a high-Q microdisk resonator and its application for SERS sensing is studied. A model for interaction of resonant nanoparticles with high-Q resonators is developed and the optimal parameters for the design of coupled microdisk resonator and a plasmonic nanoparticle are calculated. The possible of resonant plasmonic nanoparticle trapping and alignment in an SiN microdisk resonator optical trap is also shown.

Presented is a radiometric sensor and associated electromagnetic propagation models, developed to facilitate non-invasive core body temperature extraction. The system has been designed as a close-proximity sensor to detect thermal emissions radiated from deep-seated tissue 1 cm – 3 cm inside the human body. The sensor is intended for close proximity health monitoring applications, with potential implications for deployment into the improved astronaut liquid cooling garment (LCG). The sensor is developed for high accuracy and resolution. Therefore, certain design issues that distort the close proximity measurement have been identified and resolved. An integrated cavity-backed slot antenna (CBSA) is designed to account for antenna performance degradation, which occurs in the near field of the human body. A mathematical Non-Contact Model (NCM) is subsequently used to correlate the observed brightness temperature to the subsurface temperature, while accounting for artifacts induced by the sensor’s remote positioning from the specimen. In addition a tissue propagation model (TPM) is derived to model incoherent propagation of thermal emissions through the human body, and accounts for dielectric mismatch and losses throughout the intervening tissue layers. The measurement test bed is comprised of layered phantoms configured to mimic the electromagnetic characteristics of a human stomach volume; hence defines the human core model (HCM). A drop in core body temperature is simulated via the HCM, as the sensor monitors the brightness temperature at an offset distance of approximately 7 mm. The data is processes through the NCM and TPM; yielding percent error values < 3%. This study demonstrates that radiometric sensors are indeed capable of subsurface tissue monitoring from the near field of the body. However, the following components are vital to achieving an accurate measurement, and are addressed in this work: 1) the antenna must be designed for optimum functionality in close proximity to biological media; 2) a multilayer phantom model is needed to accurately emulate the point of clinical diagnosis across the tissue depth; 3) certain parameters of the non-contact measurement must be known to a high degree of accuracy; and 4) a tissue propagation model is necessary to account for electromagnetic propagation effects through the stratified tissue.

Near Field Communication (NFC) är en teknik som möjliggjort utvecklingen av vardagliga betalningar med hjälp av mobiltelefonen. I Sverige är betalningar med NFC-tekniken i mobiltelefoner fortfarande i introduktionsfasen. För att denna teknik ska ha möjlighet att fungera som ett komplement till redan befintliga betallösningar, granskas därför möjligheten för NFC-teknik som betallösningsmetod med inriktning på säkerhetsaspekter. Syftet med uppsatsen är att granska säkerhetsaspekter för NFC-teknik som mobil betallösningsmetod samt analysera dessa aspekter för att få djupare kunskap för NFC-teknologins möjligheter. Kunskapen har erhållits genom en litteraturstudie samt kompletterande av en intervju för att få bredd i informationsbehandlingen. Resultatet av studien visar att NFC-teknologin som betallösningsmetod kan påverkas av ett antal säkerhetsaspekter. För att NFC-tekniken skall nå en bredd i marknaden måste flertalet aktörer samarbeta för en standardisering i användandet av tekniken. / Near Field Communication (NFC) is a technology that enables the development of payments using the mobile phone. In Sweden, payments with NFC technology in mobile phones are still in the introductory phase. To ensure that the proposed technology can be utilized as a complement to existing payment options, one must consider the safety aspects of said construct. In this thesis we will review the technology with a focus on safety aspects. The purpose of this thesis is to review the security aspects of NFC technology for mobile payment and analyze these aspects in order to gain deeper knowledge of NFC technology opportunities. The knowledge has been obtained through a literature review, complemented by an interview to get a wide knowledge about the information. The results of the study show that NFC technology as a payment option can be affected by a number of safety issues. To ensure a viable market share, operators utilizing NFC technology must cooperate to standardize the implementation.

Indiana University-Purdue University Indianapolis (IUPUI) / The details of Polarization Modulation Near-Field Scanning Optical Microscopy (PM-NSOM) are presented. How to properly calibrate and align the system is also introduced. A measurement of Muscovite crystal is used to display the capabilities of the setup. Measurements of supported Lβʹ 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipid bilayers are presented, emphasizing how it was tooled in exploiting the anisotropic nature of the acyl chains. A discussion of how the effective retardance (ΔS = 2π( n_e-n_o )t/λ) and the direction of the projection of the acyl chains (θ) are measured simultaneously is given, (where t is the thickness of the bilayer and λ is the wavelength of light used). It is shown from ΔS the birefringence (ne-no) of the bilayer is determined, by assuming the acyl chain tilt with respect to the membrane's normal to be ϕ ≈ 32. Time varying experiments show lateral diffusions of ~ 2 x 10-12 cm2/s. Temperature controlled PM-NSOM is shown to be a viable way to determine the main phase transition temperature (Tm) for going from the gel Lβʹ to liquid disorder Lα state of supported DPPC bilayers. A change of ΔS ~ (3.8 +/- 0.3 mrad) at the main phase transition temperature Tm (≈41^o C) is observed. This agrees well with previous values of (ne-no) and translates to an assumed <ϕ> ~ 32^o when T < Tm and 0^o when T > Tm. Evidence of supper heating and supper cooling will be presented, along with a discussion of the fluctuations that occur around Tm. Finally it is shown how physical parameters such as the polarizability are extracted from the data. Values of the transverse (αt) and longitudinal (αl) polarizabilites of the acyl chains are shown to be, αt = 44.2 Å3 and αl = 94.4 Å3, which correspond well with the theoretical values of a single palmitic acid (C16) αt = 25.14 Å3 and αl = 45.8 Å3.

This work presents the first demonstration of a semiconductor based plasmonic near-field superlens, utilizing highly doped GaAs to generate infrared optical images with a spatial resolution beyond the difraction limit. Being easily transferable to other semiconductor materials, the concept described in this thesis can be exploited to realize spectrally adjustable superlenses in a wide spectral range. The idea of superlensing has been introduced theoretically in 2000, followed by numerous publications including experimental studies. The effect initiated great interest in optics, since in contrast to difraction limited conventional optical microscopy it enables subwavelength resolved imaging by reconstructing the evanescent waves emerging from an object. With techniques like scanning near-field optical microscopy (SNOM) and stimulated emission depletion (STED) being already successfully established to overcome the conventional restrictions, the concept of superlensing provides a novel, different route towards high resolution. Superlensing is a resonant phenomenon, relying either on the excitation of surface plasmons in metallic systems or on phonon resonances in dielectric structures. In this respect a superlens based on doped semiconductor benefits from the potential to be controlled in its operational wavelength by shifting the plasma frequency through adjustment of the free carrier concentration. For a proof of principle demonstration, we investigate a superlens consisting of a highly n-doped GaAs layer (n = 4 x 10^18 cm-3) sandwiched between two intrinsic layers. Recording near-field images of subwavelength sized gold stripes through the trilayer structure by means of SNOM in combination with a free-electron laser, we observe both enhanced signal and improved spatial resolution at radiation wavelengths close to l = 22 µm, which is in excellent agreement with simulations based on the Drude-Lorentz model of free electrons. Here, comparative investigations of a purely intrinsic reference sample confirm that the effect is mediated by the charge carriers within the doped layer. Furthermore, slightly differently doped samples provide indications for the expected spectral shift of the resonance. According to our calculations, the wavelength range to be exploited by n-GaAs based superlenses reaches far into the terahertz region, whereas other semiconductor materials are required to explore the near infrared.

The objective of the proposed research is the design and fabrication of a novel stand-alone wireless robust system with enhanced hardware-enabled authentication and anti-counterfeiting capabilities. The system consists of two major components; the near-field certificates of authenticity (CoA), which serve as authenticity vouchers of the products they are attached to, and a microcontroller-enabled, low-power and low-cost reader. Small-sized passive physical three-dimensional structures that are composed of extremely cheap conductive and dielectric materials are shown to yield a unique and repeatable RF signature in a small portion of the frequency spectrum when brought in the reactive and radiating near-field regions of an array of miniature antennas. The multidimensional features of these CoAs, or in other words their signature or fingerprint, are cryptographically signed and digitally stored. The contactless signature validation procedure, in which an attempt to associate the near-field signature response of the physical CoA with the digitized signature, is carried out by the reader designed and fabricated. This low-cost reader operates autonomously and in an offline fashion. The feasibility and performance robustness of the system, in terms of accuracy, consistency and speed of capturing of the signatures, is rigorously assessed with a wide array of tests. Moreover, the entropy, or uncertainty, of the signatures generated by the system are empirically quantified and verified to achieve a virtually impossible false alarm. The aforementioned characteristics of the realized authentication system make it applicable to a vast array of physical objects that needs protection against counterfeiters.

Le principe de la RMN repose sur la détection de l'aimantation provenant de spin des noyaux atomiques tels que 13C, 31P et 1H. L'échantillon est placé dans un champ magnétique statique, qui polarise l'ensemble des spins. Ces derniers sont ensuite excités par les impulsions radiofréquences (environ un mètre de longueur d'onde), qui font basculer l'aimantation de ces spins dans le plan transversal. Lorsque l'aimantation retourne à sa position d'équilibre, il génère un champ électromagnétique qui est classiquement détecté par une antenne réceptrice (bobine avec un circuit d'accord/d'adaptation) à couplage inductif. Dans ce travail, nous proposons l'utilisation d'une sonde de taille micrométrique placée au voisinage de l'objet d'intérêt, à une distance bien plus courte que la longueur d'onde du signal de RMN rayonné. Notre microsonde présente des caractéristiques innovantes (i) un couplage capacitif (composante du champ électrique), (ii) une dimension réduite pour un positionnement précis, qui assure la détection du signal de RMN de l'échantillon et (iii) une détection à large bande, ce qui permet de l'utiliser pour détecter différents noyaux sans être accordée à la fréquence de Larmor. Pour vous présenter cette nouvelle alternative, les outils nécessaires à la compréhension de ce travail, en l'occurrence le principe de la RMN et de l'IRM et une introduction de la théorie du champ proche électrique sont donnés. Nous avons fait aussi un état de l'art des méthodes et techniques existant pour mesurer le signal RMN afin de recenser les avantages qu'un tel système (méthode : couplage capacitif et dispositif : microsonde de champ proche) peut apporter à la technique RMN. Ensuite, nous avons caractérisé notre microsonde pour améliorer sa détection hyper localisée, nous avons démontré que le signal RMN récupéré par notre antenne peut être décrit par l'expression du champ proche électrique :E(x, z) = A(Kz ) exp(i(z/L)) exp(−x/L) + Terme Propagatif. Enfin, nous avons appliqué notre système à des études RMN comme la spectroscopie, la relaxométrie ou encore de l'imagerie RMN. Nous avons aussi énoncé certains projets potentiels à la continuité de ce travail. / The principle of NMR is based on the detection of the magnetization originating from the spin of atomic nuclei such as 13C, 31P and 1H. The sample is placed in a static magnetic field, which polarizes the ensemble of spins and it is excited by radiofrequency pulses (wavelength about one meter), that tilt the axis of the magnetization. When the magnetization returns to equilibrium, it generates an electromagnetic field which is classically detected by a receiving antenna (coil with atuning/matching circuit) in inductive coupling.In this work, we propose the use of a micrometer-sized probe positioned in the vicinity of the object of interest, at a distance well shorter than the wavelength of the radiated NMR signal.Our microprobe presents innovative characteristics (i) a capacitive coupling (electric field component), (ii) reduced dimensions for an accurate positioning, which ensure the detection of NMR signal from the sample and (iii) it has a broadband, which allows use to detect any nuclei without being tuned to the Larmor frequency.To introduce you this new alternative, the tools necessary to the understanding of this work, in this case the principle of NMR/MRI and an introduction of the theory of the electric near field are given initially.We made also a state of the art of existing methods and techniques for measuring the NMR signal to identify the benefits that such a system (method : capacitive coupling and device : microprobe near field) can bring to the NMR technique.Then, we have characterized our microprobe to enhance its localized detection due to its small size (127 μm in diameter and 2mm in length). In this stage of characterization, we demonstrated that the NMR signal recovered by our antenna can be described by the electric near field expression :E(x, z) = A(Kz ) exp(i(z/L)) exp(−x/L) +Propagative TermFinally, we applied our system to make NMR studies such as spectroscopy, the relaxometry and NMR Imaging. We have outlined some potential projects to the continuity of this work.