Lydia ALVAREZ^* and Mufei XIAO¹

Instituto de Ingenieria, Universidad Autonoma de Baja California, Blvd. Benito Juarez, esq. Calle de la Normal, Col. Insurgentes Este, CP 21280, Mexicali Baja California, Mexico
¹Centro de Ciencias de la Materia Condensada, Universidad Nacional Autonoma de Mexico, Apartado Postal 2681, CP 22800 Ensenada, Baja California, Mexico

(Received November 15, 2005; Accepted February 8, 2006)

Numerical simulations have been carried out in the framework of waveguide theory to model collection mode scanning near-field optical microscopy (SNOM). The theoretical model includes the optical fiber end and describes the metal coated aperture on the probe tip. The developed formalism goes beyond the existing Bethe–Bouwkamp theories for electromagnetic transmission of subwavelength apertures. The finite coating and optical fiber end are now taken into account. The new features enable us to simulate the near-field probes that are widely used in the collection mode SNOM. The emphases of the numerical analyses have been mainly on the resolution mechanism of the microscopy. Influence on the resolution from important parameters of the probe tips, such as the size of the apertures and the probe-sample distance, is extensively studied. The resolution dependence has been analyzed in the light of the near-field coupling efficiency of the probe tip. An optimum tip size has been found which is balanced between the significant signal transmission and the resolution of the device.

Key words: near-field, subwavelength aperture, collection-mode, resolution, SNOM

^*Corresponding author. E-mail address: lydia@iing.mxl.uabc.mx