Integrated polymer photonics : fabrication, design, characterization and applications

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Optical Coherence Tomography and Its Non-medical Applications

Optical coherence tomography (OCT) is a promising non-invasive non-contact 3D imaging technique that can be used to evaluate and inspect material surfaces, multilayer polymer films, fiber coils, and coatings. OCT can be used for the examination of cultural heritage objects and 3D imaging of microstructures. With subsurface 3D fingerprint imaging capability, OCT could be a valuable tool for enhancing security in biometric applications. OCT can also be used for the evaluation of fastener flushness for improving aerodynamic performance of high-speed aircraft. More and more OCT non-medical applications are emerging. In this book, we present some recent advancements in OCT technology and non-medical applications

DESIGN, FABRICATION AND TESTING OF HIERARCHICAL MICRO-OPTICAL STRUCTURES AND SYSTEMS

Micro-optical systems are becoming essential components in imaging, sensing, communications, computing, and other applications. Optically based designs are replacing electronic, chemical and mechanical systems for a variety of reasons, including low power consumption, reduced maintenance, and faster operation. However, as the number and variety of applications increases, micro-optical system designs are becoming smaller, more integrated, and more complicated. Micro and nano-optical systems found in nature, such as the imaging systems found in many insects and crustaceans, can have highly integrated optical structures that vary in size by orders of magnitude. These systems incorporate components such as compound lenses, anti-reflective lens surface structuring, spectral filters, and polarization selective elements. For animals, these hybrid optical systems capable of many optical functions in a compact package have been repeatedly selected during the evolutionary process. Understanding the advantages of these designs gives motivation for synthetic optical systems with comparable functionality. However, alternative fabrication methods that deviate from conventional processes are needed to create such systems. Further complicating the issue, the resulting device geometry may not be readily compatible with existing measurement techniques. This dissertation explores several nontraditional fabrication techniques for optical components with hierarchical geometries and measurement techniques to evaluate performance of such components. A micro-transfer molding process is found to produce high-fidelity micro-optical structures and is used to fabricate a spectral filter on a curved surface. By using a custom measurement setup we demonstrate that the spectral filter retains functionality despite the nontraditional geometry. A compound lens is fabricated using similar fabrication techniques and the imaging performance is analyzed. A spray coating technique for photoresist application to curved surfaces combined with interference lithography is also investigated. Using this technique, we generate polarizers on curved surfaces and measure their performance. This work furthers an understanding of how combining multiple optical components affects the performance of each component, the final integrated devices, and leads towards realization of biomimetically inspired imaging systems

Multimodal probe for optical coherence tomography epidetection and micron-scale indentation

We present a multimodal ferrule-top sensor designed to perform the integrated epidetection of Optical Coherence Tomography (OCT) depth-profiles and micron-scale indentation by all-optical detection. By scanning a sample under the probe, we can obtain structural cross-section images and identify a region-of-interest in a nonhomogeneous sample. Then, with the same probe and setup, we can immediately target that area with a series of spherical-indentation measurements, in which the applied load is known with a μN precision, the indentation depth with sub-μm precision and a maximum contact radius of 100μm. Thanks to the visualization of the internal structure of the sample, we can gain a better insight into the observed mechanical behavior. The ability to impart a small, confined load, and perform OCT A-scans at the same time, could lead to an alternative, high transverse resolution, Optical Coherence Elastography (OCE) sensor

The smart contact lens: from an artificial iris to a contact lens display

Contactlenzen zijn ruim gekend als passieve hulpmiddelen voor visuele correctie, maar in het laatste decennium is er een nieuw onderzoeksdomein ontstaan naar zogenaamde 'slimme' contactlenzen. Door het toevoegen van elektronische componenten en andere actieve elementen kunnen nieuwe functionaliteiten aan contactlenzen worden gegeven zoals het meten van biomedische parameters, actieve visuscorrectie en Augmented Reality. Met het oog op potentiele toepassingen in actieve visuscorrectie en Augmented Reality, werd er in dit onderzoek werd gekeken hoe klassieke LCD technologie geïntegreerd kan worden in contactlenzen. Gebaseerd op bestaande fabricagemethoden van flexibele beeldschermen werd een nieuw productieproces opgesteld dat toeliet om een sferisch vervormde vloeibaarkristal-cel te produceren die dun genoeg was om in een contactlens geïntegreerd to worden. Hierna werden de eerste mogelijke applicaties zoals een artificiële iris en een actieve multifocaallens verkend en werd er gekeken wat de verdere uitdagingen waren om tot een heus contactlensbeeldscherm te komen

Compact microscopy systems with non-conventional optical techniques

This work has been motivated by global efforts to decentralize high performance imaging systems through frugal engineering and expansion of 3D fabrication technologies. Typically, high resolution imaging systems are confined in clinical or laboratory environment due to the limited means of producing optical lenses on the demand. The use of lenses is an essential mean to achieve high resolution imaging, but conventional optical lenses are made using either polished glass or molded plastics. Both are suited for highly skilled craftsmen or factory level production. In the first part of this work, alternative low-cost lens-making process for generating high quality optical lenses with minimal operator training have been discussed. We evoked the use of liquid droplets to make lenses. This unconventional method relies on interfacial forces to generate curved droplets that if solidified can become convex-shaped lenses. To achieve this, we studied the droplet behaviour (Rayleigh-Plateau phenomenon) before creating a set of 3D printed tools to generate droplets. We measured and characterized the fabrication techniques to ensure reliability in lens fabrication on- demand at high throughput. Compact imaging requires a compact optical system and computing unit. So, in the next part of this work, we engineered a deconstructed microscope system for field-portable imaging. Still a core limitation of all optical lenses is the physical size of lens aperture – which limits their resolution performance, and optical aberrations – that limit their imaging quality performance. In the next part of this work, we investigated use of computational optics-based optimization approaches to conduct in situ characterization of aberrations that can be digitally removed. The computational approach we have used in this work is known as Fourier Ptychography (FP). It is an emerging computational microscopic technique that combines the use of synthetic aperture and iterative optimization algorithms, offering increased resolution, at full field-of-view (FOV) and aberration-removal. In using FP techniques, we have shown measurements of optical distortions from different lenses made from droplets only. We also, investigated the limitations of FP in aberration recovery on moldless lenses. In conclusion, this work presents new opportunities to engineer high resolution imaging system using modern 3D printing approaches. Our successful demonstration of FP techniques on moldless lenses will usher new additional applications in digital pathology or low-cost mobile health

Glassy Materials Based Microdevices

Microtechnology has changed our world since the last century, when silicon microelectronics revolutionized sensor, control and communication areas, with applications extending from domotics to automotive, and from security to biomedicine. The present century, however, is also seeing an accelerating pace of innovation in glassy materials; as an example, glass-ceramics, which successfully combine the properties of an amorphous matrix with those of micro- or nano-crystals, offer a very high flexibility of design to chemists, physicists and engineers, who can conceive and implement advanced microdevices. In a very similar way, the synthesis of glassy polymers in a very wide range of chemical structures offers unprecedented potential of applications. The contemporary availability of microfabrication technologies, such as direct laser writing or 3D printing, which add to the most common processes (deposition, lithography and etching), facilitates the development of novel or advanced microdevices based on glassy materials. Biochemical and biomedical sensors, especially with the lab-on-a-chip target, are one of the most evident proofs of the success of this material platform. Other applications have also emerged in environment, food, and chemical industries. The present Special Issue of Micromachines aims at reviewing the current state-of-the-art and presenting perspectives of further development. Contributions related to the technologies, glassy materials, design and fabrication processes, characterization, and, eventually, applications are welcome