Influence of tip modulation on image formation in scanning near-field optical microscopy

Modulation of the probe height in a scanning near-field optical microscope (SNOM) is a technique that is commonly used for both distance control and separation of the near-field signal from a background. Detection of higher harmonic modulated signals has also been used to obtain an improvement in resolution, the elimination of background, or artifacts in the signal. This article presents a theoretical model for the effects induced in SNOM images by modulation of the probe. It is shown that probe modulation introduces a spatial filter into the image, generally suppressing propagating field components and enhancing the strength of evanescent field components. A simple example of detection of a single evanescent field above a prism is studied in some detail, and a complicated dependence on modulation parameters and waveform is shown. Some aspects of the application of this theory in a general experimental situation are discussed. Simulated images are displayed to explicitly show the effects of varying modula...

[1]  J. H. Park,et al.  Resolution enhancement in a reflection mode near-field optical microscope by second-harmonic modulation signals. , 2000, Optics letters.

[2]  S. Kawata,et al.  Near-field scanning optical microscope with a metallic probe tip. , 1994, Optics letters.

[3]  Lukas Novotny,et al.  Facts and artifacts in near-field optical microscopy , 1997 .

[4]  M. Allegrini,et al.  Artifact-free near-field optical imaging by apertureless microscopy , 2000 .

[5]  Jean-Jacques Greffet,et al.  Theory of electromagnetic field imaging and spectroscopy in scanning near-field optical microscopy , 2000 .

[6]  P. Royer,et al.  Analysis of the influence of the tip vibration in the formation of images in apertureless scanning near-field optical microscopy , 2000 .

[7]  P. Royer,et al.  Apertureless near-field optical microscopy: influence of the illumination conditions on the image contrast. , 1998, Applied optics.

[8]  O. Marti,et al.  Modulated shear–force distance control in near-field scanning optical microscopy , 2000 .

[9]  Instrumental developments and recent experiments in near-field optical microscopy , 1996 .

[10]  R. Carminati,et al.  Optical content and resolution of near-field optical images: Influence of the operating mode , 1997 .

[11]  A. C. Boccara,et al.  Near field optical microscopy by local perturbation of a diffraction spot , 1994 .

[12]  G. Wurtz,et al.  Imaging a GaAlAs laser diode in operation using apertureless scanning near-field optical microscopy , 1999 .

[13]  R. Toledo-Crow,et al.  Near‐field differential scanning optical microscope with atomic force regulation , 1992 .

[14]  E. Betzig,et al.  Combined shear force and near‐field scanning optical microscopy , 1992 .

[15]  R. Carminati,et al.  Image formation in near-field optics , 1997 .

[16]  Fritz Keilmann,et al.  Enhanced dielectric contrast in scattering-type scanning near-field optical microscopy , 2000 .

[17]  R. Toledo-Crow,et al.  Correlative imaging in scanning near‐field optical microscopy , 1993 .

[18]  A. Boccara,et al.  Reflection-mode scanning near-field optical microscopy using an apertureless metallic tip. , 1997, Applied optics.

[19]  A. Lahrech,et al.  Electric field intensity variation in the vicinity of a perfectly conducting conical probe: Application to near‐field microscopy , 1998 .