Near field scanning optical microscope

Durand Y, Woehl J C, Viellerobe B, Gdhde W and Orrit M 1999 New design of a cryostat-mounted scanning near-field optical microscope for single molecule spectroscopy Rev. Sc/. Instrum. 70 1318-25... 

Sugiura, T., Okada, T., Inouye, Y Nakamura, O. and Kawata, S. (1997) Gold-bead scanning near-field optical microscope with laser-force position control. Opt. Lett., 22, 1663-1665. 

The concept of the STM has initiated, besides the AFM, a huge family of scanning probe microscopes (SPM), including lateral force microscopes and scanning near field optical microscopes. All these instruments are built up in a very similar way and differ only in the detected interaction between the probe and the sample. We start our discussion with a summary of the common essential parts of all SPMs. 

Fig. 3. Typical setup of a scanning near-field optical microscope. Excitation light is coupled into a single-mode fiber with a metal coated taper at its far end. The light emitted by the aperture illuminates a region of the samples whose size is determined by the aperture diameter and the distance between probe and sample. Light from the interaction region is collect using a conventional optical microscope.

A scanning method for each observation may improve the spatial resolution. A LSM with confocal optics and a scanning near-field optical microscope (SNOM) can provide finer spatial resolution with a limit of a few nanometers. The highest... 

Schematic pictures showing the modes of operation of different probe microscopes, (a) An atomic force microscope and (b) a scanning near-field optical microscope.

C. Single-Molecule Fluorescence Spectroscopy with a Scanning Near-Field Optical Microscope... 

While some breakthrough technologies of scanning near-field optical microscope have been developed to overcome the diffractimi limit to increase resolution, these near-field techniques require the distance between the tip and the specimen surface to be in the order of mie to several percents of a wavelength, normally less than 1 pm. However, in nanofluidics and lab-on-a-chip, the channels are mostly enclosed ones and the solid walls are more than 100 pm thick, and hence, the near-field scanning microscopes cannot be appUed to nanofluidics. For lab-on-a-chip appUcatimi, far-field nanoscopy, where the working distance is similar to that of conventional cmifocal microscope, is required for nanofluidics apphcatimis. 

Fig. 4.4 Schematic diagram of an aperture-type scanning near-field optical microscope. TSL Ti Sapphire laser, GP Grating pair, ODL Optical delay line, CH Mechanical chopper wheel, CWL CW laser, XL Xe lamp, WP Wave plates, FC Fiber coupler, OF Optical fiber, S Sample substrate, NFP Near-field probe, PST Piezo driven stage, OB Objective lens, POL Polarizer, FIL Optical filter, MC Monochromator, CCD Charge coupled device, PD Photodiode...

Figure 13 A shear-force scanning near-field optical microscope uses an optical fiba- probe, formed into a sharp tip, coated with A1 and with a subwavelength apertnre at its apex, to conduct nearfield excitation of a sample. Effectively, it provides a nondiffracted light source suitable for photolithography.

Evanescent fields decay rapidly in the distance of sub-microns from some localized surface and cannot be usually observed, but they are enhanced by excitation of SPs and strongly depend upon nanometric structure of ultrathin films. Recently, evanescent fields are of great interest to evaluate nanometric spatial characteristics of ultrathin films and to fabricate ultrahigh-density optical memory, nano-devices, and so on [7]-[9]. And many types of scanning near-field optics microscope (SNOM) utilizing evanescent fields have been developed [10)-[12]. 

Muller, A.-D. Muller, R Hietschold, M., Electrochemical pattern formation in a scanning near-field optical microscope. Applied Physics A Materials Science Processing 1998, 66, S453-S456. 

Guttroff, G., J. M. Keto, C. K. Shih, A. Anselm and B. G. Streetman (1996). "A design of reflection scanning near-field optical microscope and its application to algaas/gaas heterostructures." Applied Physics Letters 68(25) 3620-3622. 

Kramer, A., T. Hartmann, S. M. Stadler and R. Guckenberger (1995). "An optical tip-sample distance control for a scanning near-field optical microscope." Ultramicroscopy 61(1 -4, Select Papers from the 3rd International Conference on Near-Field Optics and Related Techniques, 1995) 191-195. 

Silva, T. J., A Scanning Near-Field Optical Microscope with Magneto-Optic Kerr Effect Contrast for the Imaging ofMagnetic Domains with 200 A Resolution. 1994, University of California, San Diego. 

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