Measurements of Radiation Pressure on Diffractive Films

One of the few ways to reach distant stars is by radiation pressure, in which photon momentum is harnessed from free sunlight or extraordinarily powerful laser systems. Large but low mass light-driven sails reflect photons and transfer momentum to the sailcraft, providing large velocity from continuous acceleration. Over the past decade, demonstrative reflective light sail missions were enabled by cost-efficient small satellites and the emerging private space economy. The maneuver of these metal-coated polyimide films is mechanically cumbersome because the sail must be rapidly tilted towards and away from the sun line during navigation. Modern diffractive films such as high-efficiency single-order gratings, liquid crystal cycloidal diffractive wave-plates, and meta-material gratings may provide enhanced control schemes with radiation pressure tangential to the sail surface. The potential to replace motorized control components with all-optical components also offers a reduction in mass and the risk of mission failure. Before spending considerable resources sending a rocket to deploy a solar sail, it must be verified that the sail will behave as expected in a lab on Earth. This is challenging since Earth’s gravity, electro-static forces, thermal effects, and environment vibrations exceed the relatively weak effects of radiation pressure. In this dissertation, we designed and constructed an opto-mechanical torsional pendulum in a vacuum environment that measures radiation pressure on diffraction films with sub-nano-Newton precision. With the system, we observed a large component of force parallel to the surface of a diffraction grating owing to “grating momentum”. Furthermore, we proposed, designed, and validated Diffractive Beam-Rider structures that enable spatially varying forces to pull and align the sailcraft to the beam. We parametrically “cooled” the turbulence on the Beam-Rider, which demonstrates its potential for implementation on a laser sail. This experimental stability verification was performed on a centimeter-sized bi-grating and a diffractive axicon with one and two-dimensional restoring force, respectively

Efficient Photonic Integrated Circuits – Optimizing Fiber-to-chip Coupling, Modulation, and Detection

Photonic integrated circuits (PICs) are attracting attention in a wide range of applications due to their superior performance over traditional discrete photonic devices. However, the development of PICs is bottlenecked by the integration of different fundamental building blocks. High sensitivity and diverse material properties hinder the realization of a monolithic photonic integrated circuit platform. High-efficiency solutions for photonic device integration are critical for making high-performance and low-cost devices. The objective of this work is to demonstrate high-efficiency optimization methods for a comprehensive photonic integrated chip system. This work analyzes the transition of optical signal waves between each component in a PIC and optimizes the efficiency while using cost-effective methods. Specifically, we present a plasmonic vertical coupler for out-of-plane fiber coupling with a compact footprint, and an efficient edge coupling method that provides ¡ 3dB connector-to-connector loss, a bi-layer grating coupler optimized for III-V photodiode detection that achieved more than 70% coupling efficiency, and an electro-optic modulator that has optimal optical or electrical mode overlap & transitions. This work details waveguide on-chip coupling, waveguides inter-layer coupling, and mode transition between the various materials and devices. These were optimized using a combination of the following methods: ber splicing, mode matching, mode conversion, mode confinement analysis, and piece-wise bonding. For each optimization method, the fundamental principles, simulations, and experimental results are illustrated. Overall, this work has realized improvements in the hybrid integration of various materials on the same integrated photonics platform

Photonic Jet: Science and Application

Photonic jets (PJs) are important mesoscale optical phenomena arising from electromagnetic waves interacting with dielectric particles. PJs have applications in super-resolution imaging, sensing, detection, patterning, trapping, manipulation, waveguiding, signal amplification and high-efficiency signal collection, among others. This reprint provides an overview of the field and highlights recent advances and trends in PJ research

Roadmap on structured light

Structured light refers to the generation and application of custom light fields. As the tools and technology to create and detect structured light have evolved, steadily the applications have begun to emerge. This roadmap touches on the key fields within structured light from the perspective of experts in those areas, providing insight into the current state and the challenges their respective fields face. Collectively the roadmap outlines the venerable nature of structured light research and the exciting prospects for the future that are yet to be realized

Theoretical description of radiative heat transfer: Exploring the limits of Planck's law

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física Teórica de la Materia Condensada. Fecha de lectura: 22-06-201

New frontiers in microwave metamaterials : magnetic-free non-reciprocal devices based on angular-momentum-biasing and negative-index metawaveguides

In this work, metamaterial concepts are applied to improve the design and realization of microwave components of a new generation. Conventional radiation sources, despite the mature and efficient development over the past century, maintain fundamental limitations. Slow-wave structures, such as backward-wave oscillators and traveling-wave tubes, function on the order of several operational wavelengths, leading to bulky architectures. Cherenkov radiation-based detectors are constrained to forward propagation, where the detection or diagnostic scheme may be damaged by energetic particles. Metamaterial concepts, specifically negative-index structures, provide new opportunities for these applications. In this context, we developed a detailed design of a negative-index metamaterial conducive to microwave generation. We experimentally validated a negative-index waveguide based on patterned plates of complementary split ring resonators. The design is conducive to interaction between particles and waves; it maintains a scalable negative-index band along with a longitudinal electric field component for particle interaction. The sub-wavelength resonant nature of the metamaterial allows for a compact design. In a different field of research, there is also significant need to squeeze the dimensions of microwave components. We have developed magnet-less, non-reciprocal, microwave circulators based on angular-momentum-biasing, which allow the realization of non-reciprocal devices that do not require magnets, and therefore lead to cheaper, lighter and significantly smaller devices. Angular-momentum-biasing, theoretically proposed recently in our research group, effectively mimics the collective alignment of electron spins seen in a ferromagnetic medium under a magnetic bias. Through spatiotemporal modulation, one can generate electrical rotation, leading to strong nonreciprocal response without magnetism. We have experimentally proven the theory on lumped element circulators and proposed transmission-line variations, providing over 50 dB of isolation in a range of frequency bands. This method provides efficient, easily tunable, fully integrable, compact devices that may revolutionize the future of integrated components. We have developed rigorous design principles that not only provide guidance for designs based on desired performance metrics, but also proves the passive nature of the concept. Furthermore, we have crafted mechanisms to enhance the bandwidth performance and improve linearity.Electrical and Computer Engineerin

Optical coherence tomography for characterization of nanocomposite materials

Nanocomposite materials play an increasingly important role in various application areas, be it in an industrial, medical or everyday environment. The unique properties of nanocomposites go beyond those of conventional composite materials. Because nanoparticles have a high surface-to-volume ratio such as carbon nanotubes, they can reinforce an embedding polymer host matrix mechanically, or they enhance the electrical material conductivity. A major challenge in the development of nanoparticles and nanocomposites is the control of particle size and shape, and of the uniform dispersion of nanoparticles in the host material. Conventional characterization techniques lack either resolution, or can only inspect details of small samples. In this book, the application of optical coherence tomography (OCT) for nanocomposite and nanoparticle characterization is investigated. OCT is a threedimensional imaging method with microscopic resolution. We follow a multiscale approach: Along with imaging in the micrometre to millimetre regime, we employ a light scattering model to extend the measurement range towards nanoparticle sizes. Industrial use cases pose additional challenges to OCT systems, namely robustness, small system cost and size, and an open path towards parallelization. Photonic integrated systems comply with these requirements, and they allow a dense integration of a multitude of systems on a single chip. We design and investigate silicon photonic integrated OCT systems that comprise interferometer and balanced photodetectors on a silicon chip

Roadmap for optical tweezers

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAMOptical tweezers are tools made of light that enable contactless pushing, trapping, and manipulation of objects, ranging from atoms to space light sails. Since the pioneering work by Arthur Ashkin in the 1970s, optical tweezers have evolved into sophisticated instruments and have been employed in a broad range of applications in the life sciences, physics, and engineering. These include accurate force and torque measurement at the femtonewton level, microrheology of complex fluids, single micro- and nano-particle spectroscopy, single-cell analysis, and statistical-physics experiments. This roadmap provides insights into current investigations involving optical forces and optical tweezers from their theoretical foundations to designs and setups. It also offers perspectives for applications to a wide range of research fields, from biophysics to space explorationEuropean Commission (Horizon 2020, Project No. 812780