I wanted to do a quick test with a Kretschmann Surface Plasmon Resonance setup. So I got a glass slide with 50nm coating, a 650 nm, 0.9mW laser diode, and a prism. I essentially place this as a vertical setup with the glass slide on top of the prism with immersion oil in between. I placed it vertically so that gravity keeps the prism, immersion oil, and glass slide in place.
Then I manually move the laser slowly till I see a dip in the reflected beam, but I never see any dips. I even placed a linear polarizer in front of the laser, but I still see no dips in intensity. I was wondering what the issue could be? Or is there a 3D printable vertical SPR setup that I could replicate as I am doing this at home, so a horizontal setup is a bit difficult to do without the oil leaking downwards or some other solutions on top of the gold film.