Surface plasmon resonance enhanced Goos–Hänchen and Imbert–Fedorov shifts of Laguerre–Gaussian beams

Abstract

Goos–Hänchen (GH) and Imbert–Fedorov (IF) shifts have been widely used in the precision metrology and optical sensing. Here, we make a comprehensive comparison on these two shifts under surface plasmon resonance condition. For a Laguerre–Gaussian incident beam, both the GH and IF shifts can be enhanced near the SPR angle. Both shifts increase with incident beam waist w0, then trend to some asymptotic values. The asymptotic values for GH shifts are independent of the vortex charge ℓ, while those for IF shifts are linearly proportional to ℓ. Thus, the asymptotic IF shifts are larger than asymptotic GH shifts when |ℓ|>1. For a given w0, the maximum values of GH and IF shifts are respectively w0/2(|ℓ|+1) and |ℓ|w0/2(|ℓ|+1) by optimizing simultaneously the incident angle and Au thickness. Moreover, the IF shifts are shown to be more sensitive than the GH shifts to the refractive index of surrounding media. Therefore, the IF shifts are expected to have better sensing performance.