Optical near-field

Fig. 12 Optical near-field intensity distribution at the siuface of spherical gold nanoparticle with radius of 50 nm, calculated by FDTD technique. The incident field (1,0,0) was polarized along the y-axis the field monitor plane is perpendicular to the wave propagation direction (z-axis) and located at a distance of 70 nm from the center of the sphere...

SNOM combines the optical contrast with a high lateral resolution of SPMs [55,56]. Scanning a surface with a sharp optical fibre tip within the range of the optical near field makes it possible to overcome the optical diffraction limit that restricts the resolution of conventional optical microscopy. Moreover, the SNOM probe operates at a finite distance from the surface, so that damage and distortion of delicate samples can be eliminated. The drawback of SNOM compared to other SPM methods is its relatively low resolution - around tens of nanometers [62,63]. 

H. Frey, S. Witt, K. Felderer and R. Guckenberger, High-resolution imaging of single fluorescent molecules with the optical near-field of a metal tip, Phys. Rev. Lett. 93, 200801 (2004). 

Fourier-Transform Infrared (FTIR) spectroscopy as well as Raman spectroscopy are well established as methods for structural analysis of compounds in solution or when adsorbed to surfaces or in any other state. Analysis of the spectra provides information of qualitative as well as of quantitative nature. Very recent developments, FTIR imaging spectroscopy as well as Raman mapping spectroscopy, provide important information leading to the development of novel materials. If applied under optical near-field conditions, these new technologies combine lateral resolution down to the size of nanoparticles with the high chemical selectivity of a FTIR or Raman spectrum. These techniques now help us obtain information on molecular order and molecular orientation and conformation [1],... 

Rogers, J. A., et al. (1997), Using an elastomeric phase mask for sub-100 nm photolithography in the optical near field, Appl. Phys. Lett., 70, 2658-2660. 

Karageorgiev P, Neher D, Schulzl B et al. (2005) Prom anisotropic photo-fluidity towards nanomanipulation in the optical near-field. Nature Mat 4 699-703... 

Stark PRH, Halleck AE, Larson DN (2007) Breaking the diffraction barrier outside of the optical near-field with bright, collimated light from nanometric apertures. Proc Natl Acad Sci USA 104 18902-18906... 

S. Foteinopoulou, J. P. Vigneron, and C. Vandenbem. Optical near-field excitations on plasmonic nanoparticle-based structures Optics Express, 2007, 15,4253-4267. 

Ohtsu M., Kobayashi K., Kawazoe T., Sangu S., and Yatsui T. (2002). Nanophotonics design, fabrication, and operation of nanometric devices using optical near fields. IEEE J. Sel Top. Quantum Electron. 8 839-862. 

Kramer, A., Trabesinger, W., Hecht, B. and Wild, U. P. (2002). Optical near-field enhancement at a metal tip probed by a single fluorophore. Appl Phys. Lett. 80 1652-1654. 

Ramanujam, P. S., Holme, N. C. R., and Hvilsted, S. Atomic force and optical near-field microscopic investigations of polarization holographic gratings in a liquid crystalline azobenzene side-chain polyester. Appl. Phys. Lett. 1996, 68, pp. 1329-1331. 

Figure 22. Sketch of the electric field lines E0 in the optical near field around the circular subwavelength aperture of a near-field probe with a molecular dipole D at r from the center of the aperture.

Figure 29. Time-dependent fluorescence spectra of a lipophilic carbocyanine molecule, excited by the optical near field of an aperture probe. Time averaged spectrum integrated over 17 min, wavelength shifted spectrum recorded during the eighteenth minute, after spontaneous irreversible photobleaching the background spectrum was recorded (twentieth minute). (Adopted from [96].)...

The optical near-field mieroseope reaches a resolution of better than 50 nm. The microscopes deliver high-resolution images not only of solid samples but also of the membranes of eells [148],... 

Hohensinner V, Maier I, Pittner F (2007). A gold cluster-linked immunosorbent assay optical near-field biosensor chip for the detection of allergenic beta-lactoglobuUn in processed milk matrices. J. Biotechnol, 130(4) 385-388. 

Kawazoe T, Yatsui T, Ohtsu M et al. (2006) Nanophotonics using optical near fields. J. Non-Cryst. Sol. 352 2492-2495. 

Moreover, among SNOM modifications operating in the collection mode, there is a so-called photon scanning tunnel mode, where light is incident at the angle of total internal reflection (Figure 7.9d). The optical near field localized in the neighborhood of the specimen surface is detected with a near-field probe. 

Near-field scanning optical microscopes (NSOM or SNOM) are mainly used in fluorescence and VIS measurements. They provide optical images with spatial resolution less than the Abbe s limit of Ajl. The high lateral resolution is commonly achieved by using the optical near-field, e. g. in close vicinity of a very narrow fiber tip. Figure 5.16 illustrates the design of a near-field microscope. 

R. Pomraenke, C. Ropers, J. Renard, C. Lienau, L. Lur, D. Polli, and G. Cerullo, Broadband optical near-field microscope for nanoscale absorption spectroscopy of organic materials. J. Microscopy Oxford, 229, 197 (2008). 

Fukuda T, Sumaru K, Kimura T, Matsuda H. 2001a. Observation of optical near field as photo induced surface relief formation. Jpn J Appl Phys 40 L900 L902. 

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