HEATING MECHANISMS IN A NEAR-FIELD OPTICAL-SYSTEM

A finite-difference-time-domain and two finite-difference-thermal mode ls are used to study various heating mechanisms in a near-field optica l system. It is shown that the dominant mechanism of sample heating oc curs from optical power that is transferred from the probe to a metall ic thin-film sample. The optical power is absorbed in the sample and c onverted to heat. The effects of thermal radiation from the probe's co ating and thermal conduction between the probe and the sample are foun d to be negligible. In a two-dimensional waveguide with TE polarizatio n, most of the optical power is transferred directly from the aperture to the sample. In a two-dimensional waveguide with TM polarization, t here is significant optical power transfer between the probe's aluminu m coating and the sample. The power transfer results in a wider therma l distribution with TM polarization than with TE polarization. Using c omputed temperature distributions in a Co-Pt film, we predict the rela tive size of thermally written marks in a three-dimensional geometry. The predicted mark size shows a 30% asymmetry that is due to polarizat ion effects. (C) 1997 Optical Society of America.