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Thin-films often exhibit colorful fringes along equal thickness lines because of the interference between the reflected light from the interfaces.This phenomenon allows us to estimate the film thickness with submicrometer precision [1].Recently,Capasso and his coworkers pointed out that the phase change of reflected light at an interface between lossy materials,particularity noble metals,can be engineered by using structured interfaces [2].It opens the door towards countless new applications.Inspired by the idea,we investigate the interference between two metallic interfaces and further demonstrate its applications in optical profiling.We first studied the interference between a 40 nm Au film and a fabricated plasmonic-nanodisk-array(PNA)with 200 nm pitch size and 100 nm different disk diameters.Reflection spectra were measured at different distances between the PNA and Au film.It was found that the resonance of the coupled system is extremely sensitive to the distance,and the resonance wavelength was shifted by~45 nm when the distance was tuned from 1 nm to 20 nm.Numerical study reveals that the huge resonance shift was caused by the near-field couplings between the nanodisks and the Au films,similar to the case of coupled system consisting single Au nanoparticles.In addition,we implemented this plasmonic interference phenomenon to the field of optical profiling,and demonstrated that 15 nm deep patterned grooves can be directly visualized under a low profile optical microscope with the help of Au nanodisk array,while nothing can be seen without the Au nanodisks.We believe that,with the unique properties of the coupled thin-films,this plasmonic interference technique will have many significant applications.