Optical EngineeringNanometer indicating system based on surface plasmon resonance and its applicaiton in an interferometer
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A novel method for nanometer indicating based on surface plasmon resonance (SPR) is introduced. A fiber probe with a semispherical end approaching a coated Kretschmann (1971) prism is equivalent to a four-layer prism-metal-air-fiber structure. Theoretical analysis shows that the transmitted intensity coupling into the fiber probe changes as the thickness of the air gap varies. Owing to this property, a noncontact nanometer indicating system can be built. The SpR nanometer indicator can be integrated into a heterodyne interferometer to reduce drift. Askew retroreflector is designed so that the incident angle of its first reflection surface is equal to the resonance angle of SPR to implement the integration SPR indicating experiments show that a maximum deviation of 12 nm and a resolution of 0.1 nm/nV can be achieved. Moreover, the uncertainty of an integrated interferometer whose optical path difference is 300 mm is reduced from 60 to 10 nm when air-conditioning is 0.5 °C/h.