Optimal coating thickness for enhancement of optical effects in optical multilayer-based metrologies

What is it about?

We theoretically determine an optimal configuration for a planar optical multilayer that is used to enhance the radiation pressure (RP) and the thermal heating in fiber-based metrology systems such as fiber-top cantilevers. The RP exerting on the metallic layer of the cantilever and the thermal heating due to optical absorption are enhanced. This enhancement can be employed to control the deflection and the vibration amplitude of the cantilever. The thicknesses of the cantilever and the coating layer for maximal RP are shown to be 50–60 nm and 20–40 nm, respectively, when a laser with an optical wavelength λ> 500 nm is used. The RP amplification due to the cavity effect is most effective at λ≃ 1200 nm and reaches a maximum value of 30. The heat absorption of the corresponding films is discussed. These results would be useful for optimizing the configurations of optical multilayer-based devices.

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Why is it important?

•Parameters for optimal enhancement of radiation pressure in FTCs are determined. •Film thicknesses for two typical wavelengths of 633 nm and 1064 nm are deduced. •A field enhancement of 30 at long wavelength is found.

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