Apertureless Scanning Nearfield Optical Microscopy With Ultra High Temporal Resolution

Scanning near-field optical microscopy (SNOM) is a system that can image beyond the conventional diffraction limit. It does this by collecting the information contained within evanescent fields. This unique ability to image using evanescent fields also enables SNOM to directly measure the electric field distribution in waveguides, where light is guided by total internal reflection. When SNOM is used with a spectrally resolving detector, local temporal phenomena can be detected by analysing spectral interference in the spectra collected by the probe. This spectrally resolving configuration was used to directly measure inter-modal group velocity difference in a multimode ridge waveguide and, using the modes' spatial profiles to experimentally determine the mode amplitude coefficient ratio. Such an ability to provide measurements on the local dispersion characteristics and relative modal amplitudes of guided light establishes SNOM as a route for investigating the conversion of current single mode photonic devices into multimode devices. The spectrally resolving SNOM system was also used to investigate the sources of temporal delays created by a quasi disordered scattering sample, which was based on John H. Conway's pinwheel tiling. Whilst the measurements do not create a complete picture of the scattering phenomena in this work, suggestions for improvement are offered with the aim establishing spectrally resolving SNOM systems as tools for mapping localised temporal phenomena in disordered scattering systems.

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.

"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.

Making a clear distinction is made between nano- and micro-mechanical testing for physical reasons, this monograph describes the basics and applications of the supermicroscopies AFM and SNOM, and of the nanomechanical testing on rough and technical natural surfaces in the submicron range down to a lateral resolution of a few nm. New or improved instrumentation, new physical laws and unforeseen new applications in all branches of natural sciences (around physics, chemistry, mineralogy, materials science, biology and medicine) and nanotechnology are covered as well as the sources for pitfalls and errors. It outlines the handling of natural and technical samples in relation to those of flat standard samples and emphasizes new special features. Pitfalls and sources of errors are clearly demonstrated as well as their efficient remedy when going from molecularly flat to rough surfaces. The academic or industrial scientist learns how to apply the principles for tackling their scientific or manufacturing tasks that include roughness far away from standard samples.

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.

The fundamental objective of this study is to establish a functional, practical apertureless type scanning near-field optical microscope, and to figure out the working mechanism behind it. Whereas a far-field microscope can measure the propagating field's components, this gives us little information about the features of the sample. The resolution is limited to about half of the wavelength of the illuminating light. On the other hand, the a-SNOM system enables achieving non-propagating components of the field, which provides more details about the sample's features. It is really difficult to measure because the amplitude of this field decays exponentially when the tip is moved away from the sample. The sharpness of the tip is the only limitation for resolution of the a-SNOM system. Consequently, the sharp tips are achieved by using electrochemical etching, and these tips are used to detect near-field signal. Separating the weak a-SNOM system signals from the undesired background signal, the higher demodulation background suppression is utilized by lock-in detection.