Holographic Fabrication of 3D Moiré Photonic Crystals Using Circularly Polarized Laser Beams and a Spatial Light Modulator

The authors of the article state that holographic fabrication of a 3D moiré photonic crystal is very difficult due to the coexistence of the bright and dark regions, where the exposure threshold is suitable for one region but not for the other. In this paper, the authors study the holographic fabrication of 3D moiré photonic crystals using an integrated system of a single reflective optical element (ROE) and a spatial light modulator (SLM) where nine beams (four inner beams + four outer beams + central beam) are overlapped

FABRICATION OF HIGH FIDELITY, HIGH INDEX 3D PHOTONIC CRYSTALS USING A TEMPLATING APPROACH

In this dissertation, we demonstrate the fabrication of high fidelity 3D photonic crystal through polymer template fabrication, backfilling and template removal to obtain high index inversed inorganic photonic crystals (PCs). Along the line, we study the photoresist chemistry to minimize the shrinkage, backfilling strategies for complete infiltration, and template removal at high and low temperatures to minimize crack-formation. Using multibeam interference lithography (MBIL), we fabricate diamond-like photonic structures from commercially available photoresist, SU-8, epoxy functionalized polyhedral oligomeric silsesquioxane (POSS), and narrowly distributed poly(glycidyl methacrylate)s (PGMA). The 3D structure from PGMA shows the lowest shrinkage in the [111] direction, 18%, compared to those fabricated from the SU-8 (41%) and POSS (48%) materials under the same conditions. To fabricate a photonic crystal with large and complete photonic bandgap, it often requires backfilling of high index inorganic materials into a 3D polymer template. We have studied different backfilling methods to create three different types of high index, inorganic 3D photonic crystals. Using SU-8 structures as templates, we systematically study the electrodeposition technique to create inversed 3D titania crystals. We find that 3D SU-8 template is completely infiltrated with titania sol-gel through a two-stage process: a conformal coating of a thin layer of films occurs at the early electrodeposition stage (\u3c 60 min), followed by bottom-up deposition. After calcination at 500 oC to remove the polymer template, inversed 3D titania crystals are obtained. The optical properties of the 3D photonic crystals characterized at various processing steps matches with the simulated photonic bandgaps (PBGs) and the SEM observation, further supporting the complete filling by the wet chemistry. Since both PGMA and SU-8 decompose at a temperature above 400 oC, leading to the formation of defects and cracks, a highly thermal and mechanical stable template is desired for PC fabrication. We fabricate the 3D POSS structures by MBIL, which can be converted to crack-free silica-like templates over the entire sample area (~5 mm in diameter) by either thermal treatment in Ar at 500 oC or O2 plasma, and the porosity can be conveniently controlled by O2 plasma power and time. Since POSS derivatives are soluble in HF aqueous solutions, we successfully replicate the 3D porous structures into polymers, such as PGMA and poly(dimethyl siloxane) (PDMS). We note that all the fabrication processes are conducted at room temperature, including template fabrication, infiltration and removal. Further, using 3D POSS structures as templates, here, we demonstrate the synthesis of 3D photonic crystals from silicon carbide and boron carbide, respectively, which are thermally stable above 1100 oC in Ar. These non-oxide ceramic photonic crystals are potentially useful as ultrahigh temperature thermal barrier coatings that provide thermal protection for metallic components

Functional Elements in Three-Dimensional Photonic Bandgap Materials

Functional elements in three-dimensional photonic bandgap materials have the potential to precisely control the flow of light. In this thesis a variety of different functional defect structures embedded into silicon woodpile photonic crystals are realized using a combination of direct laser writing and silicon double inversion. The optical properties of the fabricated structures are investigated both experimentally and by numerical calculations

Light to Shape the Future: From Photolithography to 4D Printing

Over the last few decades, the demand of polymeric structures with well-defined features of different size, dimension, and functionality has increased from various application areas, including microelectronics, biotechnology, tissue engineering, and photonics, among others. The ability of light to control over space and time physicochemical processes is a unique tool for the structuring of polymeric materials, opening new avenues for technological progress in different fields of application. This article gives an overview of various photochemical reactions in polymers, photosensitive materials, and structuring techniques making use of light, and highlights most recent advances, emerging opportunities, and relevant applications

Pattern-integrated interference lithography for two-dimensional and three-dimensional periodic-lattice-based microstructures

Two-dimensional (2D) and three-dimensional (3D) periodic-lattice-based microstructures have found multifaceted applications in photonics, microfluidics, tissue engineering, biomedical engineering, and mechanical metamaterials. To fabricate functional periodic microstructures, in particular in 3D, current available technologies have proven to be slow and thus, unsuitable for rapid prototyping or large-volume manufacturing. To address this shortcoming, the new innovative field of pattern-integrated interference lithography (PIIL) was introduced. PIIL enables the rapid, single-exposure fabrication of 2D and 3D custom-modified periodic microstructures through the non-intuitive combination of multi-beam interference lithography and photomask imaging. The research in this thesis aims at quantifying PIIL’s fundamental capabilities and limitations through modeling, simulations, prototype implementation, and experimental demonstrations. PIIL is first conceptualized as a progression from optical interference and holography. Then, a comprehensive PIIL vector model is derived to simulate the optical intensity distribution produced within a photoresist film during a PIIL exposure. Using this model, the fabrication of representative photonic-crystal devices by PIIL is simulated and the performance of the PIIL-produced devices is studied. Photomask optimization strategies for PIIL are also studied to mitigate distortions within the periodic lattice. The innovative field of 3D-PIIL is also introduced. Exposures of photomask-integrated, photomask-shaped, and microcavity-integrated 3D interference patterns are simulated to illustrate the richness and potential of 3D-PIIL. To demonstrate PIIL experimentally, a prototype pattern-integrated interference exposure system is designed, analyzed with the optical design program ZEMAX, and used to fabricate pattern-integrated 2D square- and hexagonal-lattice periodic microstructures. To validate the PIIL vector model, the proof-of-concept results are characterized by scanning-electron microscopy and atomic force microscopy and compared to simulated PIIL exposures. As numerous PIIL underpinnings remain unexplored, research avenues are finally proposed. Future research paths include the design of new PIIL systems, the development of photomask optimization strategies, the fabrication of functional devices, and the experimental demonstration of 3D-PIIL.Ph.D

Optical Fiber Interferometric Sensors

The contributions presented in this book series portray the advances of the research in the field of interferometric photonic technology and its novel applications. The wide scope explored by the range of different contributions intends to provide a synopsis of the current research trends and the state of the art in this field, covering recent technological improvements, new production methodologies and emerging applications, for researchers coming from different fields of science and industry. The manuscripts published in the Special issue, and re-printed in this book series, report on topics that range from interferometric sensors for thickness and dynamic displacement measurement, up to pulse wave and spirometry applications

Beyond solid-state lighting: Miniaturization, hybrid integration, and applications og GaN nano- and micro-LEDs

Gallium Nitride (GaN) light-emitting-diode (LED) technology has been the revolution in modern lighting. In the last decade, a huge global market of efficient, long-lasting and ubiquitous white light sources has developed around the inception of the Nobel-price-winning blue GaN LEDs. Today GaN optoelectronics is developing beyond lighting, leading to new and innovative devices, e.g. for micro-displays, being the core technology for future augmented reality and visualization, as well as point light sources for optical excitation in communications, imaging, and sensing. This explosion of applications is driven by two main directions: the ability to produce very small GaN LEDs (microLEDs and nanoLEDs) with high efficiency and across large areas, in combination with the possibility to merge optoelectronic-grade GaN microLEDs with silicon microelectronics in a fully hybrid approach. GaN LED technology today is even spreading into the realm of display technology, which has been occupied by organic LED (OLED) and liquid crystal display (LCD) for decades. In this review, the technological transition towards GaN micro- and nanodevices beyond lighting is discussed including an up-to-date overview on the state of the art

Manipulation of polymeric fluids through pyro-electro-hydro-dynamics

This thesis is focused on the manipulation of liquids and polymeric fluids in a non-contact and electrode-free way, exploiting pyro-electro-hydro-dynamic systems. The thesis structure provides an introduction based on the theory and the combination between pyroelectric and electro-hydro-dynamic effect, with a focus on the developed techniques, followed by the presentation of the realized works. It will be presented the fabrication of micro-optical devices, in particular micro-lenses, through pyro-electro-hydro-dynamic effect. The attention will be directed toward the fabrication methods: in fact, they have been obtained by an ink-jet technology or through self-assembly on a micro-engineered pyroelectric crystal. In the first case, a new pyro-ink-jet set-up will be proposed and further modifications of the set-up, which will improve the flexibility of the technique, will be reported. The realized micro-lenses will be optically and geometrically characterized and it will be presented the fabrication of a multi-component device as an example of application of this technique. It will be shown that pyro-ink-jet printing permit to realize very uniform micro-lenses arrays with high resolution (diameter ̴ 300 nm). The second approach is based on the self-assembly of a micro-lenses array on a micro-engineered pyroelectric crystal. It will be showed an array decoration by nano-particles, such as quantum dots, and it will be presented the di-electro-phoretic effect on the employed dots. In particular, the study will focus on the effect of the patterned substrate on the localization of the nano-particles and on the investigation of the dots pattern transfer. Moreover, it will be shown another application of pyro-ink-jet printing: the capability of this system in the highly viscous solution manipulation allows the deposition of polymeric fibers and, in particular, how a fiber like these can be used as a component in a microfluidic channel. That demonstrates pyro-ink-jet printer is also an alternative to the classic electro-spinning system, avoiding electrodes and spiraling effect during the deposition. Produced fibers show great uniformity and reach thicknesses until the nano-metric scale. Moreover, there will be illustrated all the procedures realized to produce the micro-channel

Resolution enhancement in mask aligner photolithography

Photolithographie ist eine unentbehrliche Technologie in der heutigen Mikrofabrikation integrierter elektronischer Schaltungen und optischer Komponenten auf verschiedenen Größenskalen. Die zugrundeliegende Aufgabe ist die Replikation der gewünschten Struktur, die kodiert ist in einer Photomaske, auf einem photolackbedeckten Wafer. In vergangenen Jahrzehnten gab es eine beeindruckende Weiterentwicklung photolithographischer Anlagen, was Auflösungen weit unterhalb eines Mikrometers ermöglicht. Das einfachste photolithographische Instrument ist der Maskenjustierbelichter, bei dem die Photomaske und der Wafer entweder in Kontakt oder in unmittelbare Nähe gebracht werden (Proximity-Modus), ohne zusätzliche optische Komponenten dazwischen. Vor über 50~Jahren eingeführt bleibt der Maskenjustierbelichter aufgrund seines wirtschaftlichen Betriebs das Instrument der Wahl für die Herstellung unkritischer Schichten, mit einer Auflösung von einigen Mikrometern im bevorzugten Proximity-Modus. Maskenjustierbelichter werden beispielsweise für die Herstellung von Mikrolinsen, lichtemittierende Dioden und mikromechanischen Systemen verwendet. Die erreichbare laterale räumliche Auflösung ist letztlich begrenzt durch die Beugung des Lichts an den Strukturen der Photomaske, was zu Verfälschungen der Abbildung auf dem Photolack führt. In dieser Arbeit entwickeln, präsentieren und diskutieren wir mehrere Technologien zur Auflösungsverbesserung für Maskenjustierbelichter im Proximity-Modus. Dies umfasst Photolithographie mit einer neuartigen Lichtquelle, die im tiefen Ultraviolett-Bereich emittiert, eine rigoros optimierte Phasenschiebermaske für periodische Strukturen, optische Proximity-Korrektur (Nahbereichskorrektur) angewandt auf nichtorthogonale Geometrien, und die Anwendung optischer Metaoberflächen als Photomasken. Eine Reduzierung der Wellenlänge verringert die Auswirkungen der Lichtbrechung und verbessert daher direkt die Auflösung, benötigt aber auch die Entwicklung geeigneter Konzepte für die Strahlformung und Homogenisierung der Beleuchtung. Wir diskutieren die Integration einer neuartigen Lichtquelle, ein frequenzvervierfachter Dauerstrichlaser mit einer Emissionswellenlänge von 193$\,$nm, in einem Maskenjustierbelichter. Damit zeigen wir erfolgreiche Prints von Teststrukturen mit einer Auflösung von bis zu 1,75$\,$µm bei einem Proximity-Abstand von 20$\,$µm. Bei Verwendung des selbstabbildenden Talboteffekts wird sogar eine Auflösung weit unterhalb eines Mikrometers für periodische Strukturen erzielt. Außerdem diskutieren wir die rigorose Simulation und Optimierung der Lichtausbreitung in und hinter Phasenschiebermasken, die unter schrägem Einfall belichtet werden. Mit einem optimierten Photomaskendesign kann dabei die Periode bei Belichtung unter drei diskreten Winkeln verkleinert abgebildet werden. Dies erlaubt es, Strukturen deutlich kleiner als ein Mikrometer abzubilden, wobei die Strukturen auf der Photomaske deutlich größer und damit einfacher herzustellen sind. Zudem betrachten wir eine Simulations- und Optimierungsmethode für die optische Proximity-Korrektur nicht-orthogonaler Strukturen, was deren Formtreue verbessert. die Wirksamkeit beider Konzepte bestätigen wir erfolgreich in experimentellen Prints. Die Verwendung optischer Metaoberflächen erweitert die Fähigkeiten zur Wellenfrontformung von Photomasken gegenüber etablierten Intensitäts- oder Phasenschiebermasken. Wir diskutieren zwei Designs für optische Metaoberflächen, die beide den vollen $2\,\pi$-Phasenbereich abdecken. Ein Design beinhaltet dabei noch einen plasmonischen Absorber, was zusätzliche Möglichkeiten bietet, den Transmissionskoeffizient anzupassen. Desweiteren beschreiben wir einen Algorithmus zur Berechnung des Maskenlayouts für beliebige Strukturen. Eine kontinuierliche Weiterentwicklung von Maskenjustierbelichtern ist unerlässlich, um Schritt zu halten mit der fortschreitenden Miniaturisierung in allen Bereich der Optik, der Mechanik und der Elektronik. Unsere Forschungsergebnisse ermöglichen es, die Auflösung der optischen Lithographie im Proximity-Modus zu verbessern und sich damit den zukünftigen Herausforderungen der optischen Industrie stellen zu können