Surface plasmon resonance enhanced Goos-Hanchen and Imbert-Fedorov shifts of Laguerre-Gaussian beams

Goos-Hanchen (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 w(0), 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 vertical bar l vertical bar>1. For a given w o , the maximum values of GH and IF shifts are respectively w(0)/2(vertical bar l vertical bar+1) and vertical bar l vertical bar w(0)/2(vertical bar l vertical bar+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.