Development of a Versatile Near Field Optical Imaging System
Derek Nowak, Portland State University Portland, Oregon
Co-Authors: Justin Hiester, Deepak Vedhachalam, Zechariah K. Dzegede, Erik J. Sánchez
The ability to detect optical information from optically active systems with resolutions below the diffraction limit of traditional light microscopes is of great interest of biologist and material scientists. Using the technique of Tip Enhanced Near-field Optical Microscopy, or (TENOM) (Sánchez, PRL. 1999), fluorescence imaging with ~20 nm resolution has shown to be possible. TENOM demonstrates these optical resolutions with simultaneous topographical information as well as the ability to detect with both electronic state and vibrational bond (Raman) information for single-molecule level identification. TENOM utilizes an Atomic Force Microscopy (AFM) scanning method where the imaging probe has been modified to create a localized field enhancement. The microscopes ability to image in solution is an additional feature. Unfortunately, TENOM has not seen common day use as a research tool, due primary to the level of understanding needed by the user to create suitable probes and correctly operate the microscope. Our goal has been to develop a TENOM based microscope controlled by a single low cost computer, simple control circuits using FPGA data acquisition, and simplified optical system allowing for imaging with photons from almost any visible chromophore without changing filters or excitation wavelength. Our system will be an open source system design, using only off the shelf available components. This instrument will improve upon the nominal 75 nm resolution limit of todays Near Field Scanning Microscopes.
Erik Sanchez
Interests: Development and implementation of nano-scale imaging techniques. Study of the optical interaction of light and nanometric objects in order to generate enhanced fields for fluorescence and Raman spectroscopy/microscopy. Determination of new applications for Focused Ion / Electron Beam systems towards the study of biological systems using near-field and far-field microscopies.
Derek Nowak
Physics Research Odyssey Near-Field Microscopy Multi-Photon Imaging ANSOM Project FDTD Modeling MPI Clustering LMIS Development Classes
Near-Field Microscopy
Motivation: To obtain florescence images of biological and material systems at spatial resolutions significantly lower than the diffraction limit. This technique has demonstrated optical imaging resolutions of ~40 nanometers, at room temperature and atmospheric pressure.
Side profiles of a near-field aperture probe and apertureless probe scanning over fluorescing chromophores. A fiber optic cable is tapered to a small point via chemical etching and coated with metal to confine light sent down the fiber (aperture)(Pohl, Lewis, Betzig). The light is typically collected below by the high numerical lens and directed to a photon detector in the far field.
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