The influences of the probe beam divergence on the performance of imaging surface plasmon resonance sensors

Taking probe beam divergence into account, we investigate the performance, especially the sensitivity of imaging surface plasmon resonance (SPR) sensors with Kretschmann configuration comprehensively. Corresponding to the effect on one probe spot, reflection curves of SPR with different beam divergences are calculated, which indicates that the three key parameters of the reflection curve, i.e., the minimum reflectivity, resonance width and resonance angle, all increase with the increase of the divergence, and this degrades the sensitivity of the sensors. On the other hand, because of the differences in incident angles among probe spots, the divergence-induced non-uniformity of reflectivity and sensitivity differences. Moreover, the sensors for gas detection are more dependent on the beam divergence than that for liquid detection. Some of the calculated results are verified by our experimental results.