Spatial Spectral And Temporal Resolved Scanning Optical Microscope

This instrumentation development project has made considerable progress towards its goals of producing a near field scanning optical microscope which tests the limits of spatial, temporal and spectral resolution, and which utilizes probes designed for optimal throughput and minimal probe heating. Specifically, (i) a Ti-sapphire laser has been constructed and successfully mode locked with fsec-scale pulses, (ii) a Raman detection system using a cooled CCD detector and a holographic filter has been configured, and (iii) several near-field instrument heads and electronics sub-systems built. The microscopes feature a novel constant linear motion coarse approach and improved probe-sample distance detection scheme developed under this project. A computer workstation has been purchased and programmed to (iv) model the images from the instrument in its time-resolved excess carrier studies mode, and to (v) perform ray tracing which has been used to suggest a novel rational probe design. Efforts are underway which utilize the instrument for sub psec time-resolved studies of excess carriers in silicon and to study near-field effects in Raman spectroscopy of KTP samples.

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.

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.

The near-field scanning optical microscope, or NSOM, proyides spatial resolution of surface features considerably smaller than the wavelength of the radiation used to image. We have focused on both the development and the use of the NSOM. In the former, we considered the confinement of optical fields to nanometric structures. We analyzed the delivery of light from the far-field to the near-field region in tapered optical fibers. Our analysis led to the design and development of near-field probes of that allow for the performance of relatively light-starved NSOM experiments. Using such probes, we have demonstrated a capability of using spectral contrast in near-field imaging. In studies of KTP, for example, we have performed nano-Raman spectroscopy samples, and have imaged sub-wavelength surfaces features using only Raman-scattered light. In ongoing research we have launced further efforts to improve probe design and have begun nano-Raman investigations Mercury Cadmium Telluride and semiconducting diamond.

For more than a century, microscopy has been a centerpiece of extraordinary discoveries in biology. Along the way, remarkable imaging tools have been developed allowing scientists to dissect the complexity of cellular processes at the nano length molecular scales. Nanoimaging: Methods and Protocols presents a diverse collection of microscopy techniques and methodologies that provides guidance to successfully image cellular molecular complexes at nanometer spatial resolution. The book's four parts cover: (1) light microscopy techniques with a special emphasis on methods that go beyond the classic diffraction-limited imaging; (2) electron microscopy techniques for high-resolution imaging of molecules, cells and tissues, in both two and three dimensions; (3) scanning probe microscopy techniques for imaging and probing macromolecular complexes and membrane surface topography; and (4) complementary techniques on correlative microscopy, soft x-ray tomography and secondary ion mass spectrometry imaging. Written in the successful format of the Methods in Molecular BiologyTM series, chapters include introductions to their respective topics, lists of the necessary materials and reagents, step-by-step protocols, and notes on troubleshooting and avoiding known pitfalls. Authoritative and accessible, Nanoimaging: Methods and Protocols highlights many of the most exciting possibilities in microscopy for the investigation of biological structures at the nano length molecular scales.

We propose a methodology for enhancing the diffraction limited spatial resolution attained in Raman and Fourier transform infrared microspectroscopic imaging techniques. Near-field scanning optical microscopy (SNOM) and spectroscopy employ apertureless and aperture approaches to provide ultra-high spatially resolved images at the nanometer level. In contrast, we employ conventional spectral acquisition schemes modified by spatial oversampling with the subsequent application of deconvolution techniques. As an example, this methodology is applied to flat samples using point illumination. Simulated data, assuming idealized sample concentration profiles, are presented together with experimental Raman microspectroscopic data from chemically and morphologically well-defined test samples. Intensity profiles determined using conventional mapping and imaging techniques are compared to those obtained by the probe/deconvolution methodology.

Scanning transmission electron microscopy has become a mainstream technique for imaging and analysis at atomic resolution and sensitivity, and the authors of this book are widely credited with bringing the field to its present popularity. Scanning Transmission Electron Microscopy(STEM): Imaging and Analysis will provide a comprehensive explanation of the theory and practice of STEM from introductory to advanced levels, covering the instrument, image formation and scattering theory, and definition and measurement of resolution for both imaging and analysis. The authors will present examples of the use of combined imaging and spectroscopy for solving materials problems in a variety of fields, including condensed matter physics, materials science, catalysis, biology, and nanoscience. Therefore this will be a comprehensive reference for those working in applied fields wishing to use the technique, for graduate students learning microscopy for the first time, and for specialists in other fields of microscopy.

Two-Dimensional Materials for Nonlinear Optics Comprehensive resource covering concepts, perspectives, and skills required to understand the preparation, nonlinear optics, and applications of two-dimensional (2D) materials Bringing together many interdisciplinary experts in the field of 2D materials with their applications in nonlinear optics, Two-Dimensional Materials for Nonlinear Optics covers preparation methods for various novel 2D materials, such as transition metal dichalcogenides (TMDs) and single elemental 2D materials, excited-state dynamics of 2D materials behind their outstanding performance in photonic devices, instrumentation for exploring the photoinduced excited-state dynamics of the 2D materials spanning a wide time scale from ultrafast to slow, and future trends of 2D materials on a series of issues like fabrications, dynamic investigations, and photonic/optoelectronic applications. Powerful nonlinear optical characterization techniques, such as Z-scan measurement, femtosecond transient absorption spectroscopy, and microscopy, are also introduced. Edited by two highly qualified academics with extensive experience in the field, Two-Dimensional Materials for Nonlinear Optics covers sample topics such as: Foundational knowledge on nonlinear optical properties, and fundamentals and preparation methods of 2D materials with nonlinear optical properties Modulation and enhancement of optical nonlinearity in 2D materials, and nonlinear optical characterization techniques for 2D materials and their applications in a specific field Novel nonlinear optical imaging systems, ultrafast time-resolved spectroscopy for investigating carrier dynamics in emerging 2D materials, and transient terahertz spectroscopy 2D materials for optical limiting, saturable absorber, second and third harmonic generation, nanolasers, and space use With collective insight from researchers in many different interdisciplinary fields, Two-Dimensional Materials for Nonlinear Optics is an essential resource for materials scientists, solid state chemists and physicists, photochemists, and professionals in the semiconductor industry who are interested in understanding the state of the art in the field.