Near-Field Scanning Optical Microscopy (NSOM)

For ultra-high optical resolution, near-field scanning optical microscopy (NSOM) is currently the photonic instrument of choice. Near-field imaging occurs when a sub-micron optical probe is positioned a very short distance from the sample and light is transmitted through a small aperture at the tip of this probe. The near-field is defined as the region above a surface with dimensions less than a single wavelength of the light incident on the surface. Within the near-field region evanescent light is not diffraction limited and nanometer spatial resolution is possible. This phenomenon enables non-diffraction limited imaging and spectroscopy of a sample that is simply not possible with conventional optical imaging techniques.
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Review Articles

Introduction

A principle in diffraction-limited optical microscopy requires that the spatial resolution of an image is limited by the wavelength of the incident light and by the numerical apertures of the condenser and objective lens systems.

Near-Field Scanning Optical Microscopy (NSOM) Probes

The optical probe is the most critical part of the near-field microscope for achieving high resolution images. This section introduces a few of the methods that are commonly used in near-field microscopy.

Interactive Tutorials

Aperture Scanning of a Line Grating (First Experimental NSOM)

Explore the Ash and Nicholls experiment which demonstrates the near-field resolution of a subwavelength aperture scanning microscope operating in the microwave region of the electromagnetic spectrum.

Mechanical Oscillator

The mechanical system examined in this tutorial represents the interaction of these parameters for the tuning fork oscillator and the bent optical probe NSOM configurations.

Van der Waal Forces

In the near-field scanning microscopy configuration, several forces exist between the probe tip and the specimen. Examine the dependence of these forces on the distance between the NSOM probe tip and the specimen.

NSOM Probe Aperture Throughput

Learn about NSOM Probe Aperture Throughput as both the wavelength of the light passing through the aperture and the aperture diameter can be manipulated by adjusting the value of the Wavelength and Aperture Diameter slider bars.

Unique NSOM Reflection Mode

A unique (and more difficult) configuration for NSOM imaging of opaque specimens, which can produce exceptional results is presented in this interactive Java tutorial.

Thermal Effects on NSOM Probes

Learn more about the effects of thermal heating of the NSOM probe, which occurs in the taper region due to the absorption of light by the metallic coating engulfing the exterior of the probe.

Near-Field Scanning Optical Microscope (NSOM) Simulation

See the difference between scanning with the probe in feedback mode, in which the tip height varies in response, and scanning without feedback engaged.

Literature References and Web Resources

Selected Literature References

Listed in this section are periodical location information about these books and articles, as well as providing a listing of selected original research reports from this cutting-edge field of research.

Near-Field Scanning Optical Microscopy (NSOM) Web Resources

Listed are links to resources on the web for near-field scanning optical microscopy, including university and government laboratories, technical tutorials, and microscope manufacturers.

Contributing Authors

Jeremy R. Cummings, Matthew Parry-Hill, Robert T. Sutter, Thomas J. Fellers and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.