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Monday, September 19, 2016

Waveguide-based dielectric resonance structure: a theoretical analysis to change cell–substrate separation by a repulsive optical force

Abdollah Hassanzadeh and Darya Azami

A waveguide-based dielectric resonance structure is introduced to enhance the optical pressure on a well-spread and attached cell. To calculate the change in cell–substrate separation a three-layered dielectric film, which is considered as a model for a well-spread and attached cell to its substrate, is connected to the substrate by springs. Each spring represents a single adhesion bound. The enhanced optical pressure on the sample, the changes in the cell–substrate separation distance, and strain on the cell are found. The obtained results are compared with those of both total internal reflection and interference reflection microscopes. Then, the penetration depth of the evanescent field and the enhancement factor for various modes are obtained. The results show that the enhancement factor and the optical pressure in the proposed resonance structure are 3 orders of magnitude higher than the conventional structure and the penetration depth of the evanescent wave is increased by 30 percent. We show that a measurable change in the cell–substrate distance (around 6 nm) can occur under the applied optical force. If this waveguide-based resonance structure is used in a waveguide evanescent field microscopy setup it is possible to simultaneously image and apply an effective optical pressure on cells and also to reduce the imaging time. Furthermore, there is no metal in the resonance structure to be worried about the heating and damaging biological samples.

DOI
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