Modulation methods such as homodyne and heterodyne detections are employed in A-SNOM in order to eliminate serious background effects from scattering fields. Usually, the frequency-modulated detection signal in apertureless scanning near-field optical microscopy (A-SNOM) is generally analyzed using a simple dipole-interaction model based only on the near-field interaction. However, the simulated A-SNOM spectra obtained using such models are in poor agreement with the experimental results since the effects of background signals are ignored. Accordingly, this study proposes a new phenomenological model for analyzing the A-SNOM detection signal in which the effects of both the dipole-interaction and the background fields are taken into account. It is shown that the simulated A-SNOM spectra for 6H-SiC crystal and polymethylmethacrylate (PMMA) samples are in good agreement with the experimental results. The validated phenomenological model is used to identify the experimental A-SNOM parameter settings which minimize the effects of background signals and ensure that the detection signal approaches the pure near-field interaction signal. Finally, the phenomenological model is used to evaluate the effects of the residual stress and strain in a SiC substrate on the corresponding A-SNOM spectrum.
5. Wickramasinghe, H. K. and C. C. Williams, "Apertureless near field optical microscope,", US Patent 4947034, 1990.
6. Inouye, Y. and S. Kawata, "Near-field scanning optical microscope with a metallic probe tip," Opt. Lett., Vol. 19, 159-161, 1994. doi:10.1364/OL.19.000159
7. Hillenbrand, R. and F. Keilmann, "Complex optical constants on a subwavelength scale," Phys. Rev. Lett., Vol. 85, 3029-3032, 2000. doi:10.1103/PhysRevLett.85.3029
8. Hillenbrand, R., B. Knoll, and F. Keilmann, "Pure optical contrast in scattering-type scanning near-field microscopy," J. Microsc., Vol. 202, 77-83, 2000. doi:10.1046/j.1365-2818.2001.00794.x
9. Knoll, B. and F. Keilmann, "Enhanced dielectric contrast in scattering-type scanning near-field optical microscopy," Opt. Commun., Vol. 182, 321-328, 2000. doi:10.1016/S0030-4018(00)00826-9
10. Hudlet, S., S. Aubert, A. Bruyant, R. Bachelot, P. M. Adam, J. L. Bijeon, G. Lerondel, P. Royer, and A. A. Stashkevich, "Apertureless near field optical microscopy: A contribution to the understanding of the signal detected in the presence of background field," Opt. Commun., Vol. 230, 245-251, 2004. doi:10.1016/j.optcom.2003.11.029
11. Formanek, F., Y. D. Wilde, and L. Aigouy, "Analysis of the measured signals in apertureless near-field optical microscopy," Ultramicroscopy, Vol. 103, 133-139, 2005. doi:10.1016/j.ultramic.2004.11.004
12. Gucciardi, P. G., G. Bachelier, and M. Allegrini, "Far-field background suppression in tip-modulated apertureless near-field optical microscopy," J. Appl. Phys., Vol. 99, No. 124309, 2006.
13. Stefanon, I., S. Blaize, A. Bruyant, S. Aubert, G. Lerondel R. Bachelot, and P. Royer, "Heterodyne detection of guided waves using a scattering-type scanning near-field optical microscope," Opt. Express, Vol. 13, 15782-15796, 2007.
15. Chuang, C. H. and Y. L. Lo, "An analysis of heterodyne signals in apertureless scanning near-field optical microscopy," Opt. Express, Vol. 16, 17982-18003, 2008. doi:10.1364/OE.16.017982
16. Chuang, C.-H. and Y.-L. Lo, "Signal analysis of apertureless scanning near-field optical microscopy with superlens," Progress In Electromagnetics Research, Vol. 109, 83-106, 2010. doi:10.2528/PIER10081102
17. Cvitkovic, A., N. Ocelic, and R. Hillenbrand, "Analytical model for quantitative prediction of material contrasts in scattering-type near-field optical microscopy," Opt. Express, Vol. 15, 8550-8565, 2007. doi:10.1364/OE.15.008550
18. Xie, H., Xie, H., F. M. Kong, and K. Li, "The electric field enhancement and resonance optical antenna composed of AU nanoparicles," Journal of Electromagnetic Waves and Applications, Vol. 23, No. 4, 534-547, 2009. doi:10.1163/156939309787612419
19. Hamid, A.-K. and F. R. Cooray, "Scattering by a perfect electromagnetic conducting elliptic cylinder," Progress In Electromagnetics Research Letters, Vol. 10, 59-67, 2009. doi:10.2528/PIERL09060301
20. Mohamed, M. A., E. F. Kuester, M. Piket-May, and C. L. Holloway, "The field of an electric dipole and the polarizability of a conducting object embedded in the interface between dielectric materials," Progress In Electromagnetics Research B, Vol. 16, 1-20, 2009. doi:10.2528/PIERB09050408
21. Eroglu, A. and J. K. Lee, "Far field radiation from an arbitrarily oriented hertzian dipole in an unbounded electricaly gyrotropic medium," Progress In Electromagnetics Research, Vol. 89, 291-310, 2009. doi:10.2528/PIER08122202
22. Kalaee, P. and J. Rashed-Mohassel, "Investigation of dipole radiation pattern above a chiral media using 3D bi-FDTD approach," Journal of Electromagnetic Waves and Applications, Vol. 23, No. 1, 75-86, 2009. doi:10.1163/156939309787604706
23. Zhang, S., S.-X. Gong, Y. Guan, J. Ling, and B. Lu, "A new approach for synthesizing both the radiation and scattering patterns of linear dipole antenna array," Journal of Electromagnetic Waves and Applications, Vol. 24, No. 7, 861-870, 2010. doi:10.1163/156939310791285137
24. Laviada-Martinez, J., Y. Alvarez Lopez, and F. Las-Heras, "Efficient determination of the near-field in the vicinity of an antenna for the estimation of its safety perimeter," Progress In Electromagnetics Research, Vol. 103, 371-391, 2010. doi:10.2528/PIER10031807
25. Huber, A. J., A. Ziegler, T. Köck, and R. Hillenbrand, "Infrared nanoscopy of strained semiconductors," Nature Nanotechnology, Vol. 4, 153-157, 2008.
26. Aizpurua, J., T. Taubner, F. J. García de Abajo, M. Brehm and R. Hillenbrand, "Substrate-enhanced infrared near-field spectroscopy," Opt. Express, Vol. 16, 1529-1545, 2008. doi:10.1364/OE.16.001529
27. Walford, J. N., J. A. Porto, R. Carminati, J. J. Greffet, P. M. Adam, S. Hudlet, J. L. Bijeon, A. Stashkevich, and P. Royer, "Influence of tip modulation on image formation in scanning near-field optical microscopy," J. Appl. Phys., Vol. 89, 5159-5169, 2001. doi:10.1063/1.1359153
28. Gomez, L., R. Bachelot, A. Bouhelier, G. P. Wiederrecht, S. H. Chang, S. K. Gray, F. Hua, S. Jeon, J. A. Rogers, M. E. Castro, S. Blaize, I. Stefanon, G. Lerondel, and P. Royer, "Apertureless scanning near-field optical microscopy: A comparison between homodyne and heterodyne approaches," J. Opt. Soc. Am. B, Vol. 23, 823-833, 2006. doi:10.1364/JOSAB.23.000823
29. Lo, Y. L. and C. H. Chuang, "New synthetic-heterodyne demodulation for an optical fiber interferometry," IEEE J. Quantum Electro., Vol. 37, 658-663, 2001.
30. Bek, A., "Apertureless SNOM: A new tool for nano-optics,", Ph.D. Dissertation, Max Planck Institute for Solid State Research, Germany, 2004.
31. Palik, E. D., Handbook of Optical Constants of Solids, Academic, New York, 1985.
32. Harima, H., S. Nakashima, and T. Uemura, "Raman-scattering from anisotropic LO-phonon-plasmon-coupled mode in n-type 4H-SiC and 6H-SiC," J. Appl. Phys., Vol. 78, 1996-2005, 1995. doi:10.1063/1.360174
33. Huber, A., N. Ocelic, T. Taubner, and R. Hillenbrand, "Nanoscale resolved infrared probing of crystal structure and of plasmonCphonon coupling," Nano Lett., Vol. 6, 774-778, 2006. doi:10.1021/nl060092b
34. Liu, J. and Y. K. Vohra, "Raman modes of 6H polytype of siliconcarbide to ultrahigh pressures --- A comparison with silicon and diamond," Phys. Rev. Lett., Vol. 72, 4105-4108, 1994. doi:10.1103/PhysRevLett.72.4105