Contrast And Resolution Enhancement In Near Field Optical Microscope By Using A Modulation Technique

ABSTRACT: A technique allowing for phase contrast imaging with a near-field scanning optical microscope is discussed. Background theory relating to near-field scanning optical microscopy (NSOM) is presented, in addition to relevant aspects of interferometry. A brief discussion of currently available methods for phase contrast imaging in both near-field and far-field microscopy is presented. Theory regarding the proposed technique, which exploits the interference of electrooptically modulated light and a conventional NSOM signal, is discussed in detail. Phase data using the proposed technique in a simplified configuration is presented to validate its effectiveness. The experimental arrangement used for data collection is specified. Finally, phase data obtained using the proposed technique in conjunction with a near-field microscope is examined and assessed in comparison with the results expected from prior knowledge of the sample under study.

"This dissertation describes the force regulated near-field scanning optical microscope (NSOM) and two important adaptations: one for imaging polarization contrast with a linear response, and the other for interference imaging. An introduction to near- field optics is first presented, followed by a description of the background to this work that includes the relevant references to the literature and previous results. A simple theoretical description of the NSOM in terms of scalar fields is then presented, followed by an exposition of an early but relevant rigorous vectorial interpretation of the experiment. The basic force regulated NSOM is presented: its parts, operation, and construction is described and discussed, and its imaging capabilities are shown and discussed with results from different samples. In particular, the ability of the system to simultaneously image topographical and optical characteristics of the samples is described, and the importance of separating the optical and topographical information for the correct operation of the microscope is stressed. An adaptation to the basic NSOM that permits imaging sample-dependent polarization variations with sub-wavelength resolution and with a linear sensitivity is then discussed and analyzed. Results are shown for several samples that include metal on quartz, magneto-optic media, and polymers. Lastly, an interferometric arrangement of the NSOM is presented that allows imaging of phase variations, as well as polarization variations, with a significant signal enhancement achieved with the use of a pseudo-heterodyning technique."--Abstract.

Contrast in an image is essential to distinguish features from one another and from the background. This practical handbook describes the ways in which light interacts with the specimen in the microscope.

This book presents the advances in super-resolution microscopy in physics and biomedical optics for nanoscale imaging. In the last decade, super-resolved fluorescence imaging has opened new horizons in improving the resolution of optical microscopes far beyond the classical diffraction limit, leading to the Nobel Prize in Chemistry in 2014. This book represents the first comprehensive review of a different type of super-resolved microscopy, which does not rely on using fluorescent markers. Such label-free super-resolution microscopy enables potentially even broader applications in life sciences and nanoscale imaging, but is much more challenging and it is based on different physical concepts and approaches. A unique feature of this book is that it combines insights into mechanisms of label-free super-resolution with a vast range of applications from fast imaging of living cells to inorganic nanostructures. This book can be used by researchers in biological and medical physics. Due to its logically organizational structure, it can be also used as a teaching tool in graduate and upper-division undergraduate-level courses devoted to super-resolved microscopy, nanoscale imaging, microscopy instrumentation, and biomedical imaging.

This project elucidated and examined the unique science behind the spectral and temporal contrast of near field scanning optical microscopy, illuminated the technology this enabled, and considered the limits of simultaneous position, time and spectral resolution. Specifically, (1) High-resolution, quantitative measurements of excess carrier lifetime in silicon were acquired in a novel, all-optical technique. The contrast in the images was modeled and is of interest since the resolution is significantly shorter than the carrier diffusion length. (2) a Ti-sapphire laser has been constructed and modified to decrease pump power requirements so that measurements can be made before the carriers diffuse from under the probe. Novel electron-hole droplet effects are expected. (3) Spectroscopic nano-Raman images were acquired for the first time. The Raman data illustrated interesting manifestations of a near-field in comparisons with far-field spectroscopy. (4) The first and most thorough studies of the optical and thermal properties of near-field scanning optical microscope probes gave insights which led to the development of a new generation of high throughput probes. Other results reflect instrumentation advances: (5) A new constant linear motion system useful for NSOM or other probe microscope coarse approach. (6) A new, low cost force feedback system. (7) A nanometer-resolution, kHz bandwidth, millimeter range position sensor.

Near-field optics, dealing with the interaction between optical field and matter in the nanometric region, has become an interdisciplinary field spaning physics, chemistry, materials science, electrical engineering and high density data storage. This book reflects the recent status of this rapidly growing field. It discusses the basic theories, instrumentation, novel probes, theoretical simulations, and the application of near-field optics to the fields of condensed matter physics, new materials, information storage, atom photonics, etc. It provides an overview of the research on near-field optics in the 1990s.

Full-field optical coherence microscopy (FF-OCM) is an imaging technique that provides cross-sectional views of the subsurface microstructure of semitransparent objects. The technology is based on low-coherence interference microscopy, which uses an area camera for en face imaging of the full-field illuminated object. FF-OCM benefits from the lateral imaging resolution of optical microscopy along with the capacity of optical axial sectioning at micrometer-scale resolution. The technique can be employed in diverse applications, in particular for non-invasive examination of biological tissues. This handbook is the first to be entirely devoted to FF-OCM. It is organized into four parts with a total of 21 chapters written by recognized experts and major contributors to the field. After a general introduction to FF-OCM, the fundamental characteristics of the technology are analyzed and discussed theoretically. The main technological developments of FF-OCM for improving the image acquisition speed and for endoscopic imaging are presented in part II. Extensions of FF-OCM for image contrast enhancement or functional imaging are reported in part III. The last part of the book provides an overview of possible applications of FF-OCM in medicine, biology, and materials science. A comprehensive compilation of self-contained chapters written by leading experts, this handbook is a definitive guide to the theoretical analyses, technological developments, and applications of FF-OCM. Using the rich information the book is replete with, a wide range of readers, from scientists and physicists to engineers as well as clinicians and biomedical researchers, can get a handle on the latest major advances in FF-OCM.

"This groundbreaking book focuses on near-field microscopy which has opened up optical processes at the nanoscale for direct inspection. Further, it explores the emerging area of nano-optics which promises to make possible optical microscopy with true nanometer resolution. This frontline resource helps you achieve high resolution optical imaging of biological species and functional materials. You also find guidance in the imaging of optical device operation and new nanophotonics functionalities"--EBL.