An optical biosensor is provided for detecting a bio-molecular sample by Goos-Hänchen (GH) enhancement of Aharonov-Albert-Vaidman (AAV) amplification to a surface plasmon resonance (SPR) detector. The sensor includes pre- and post-selection polarizers respectively upstream and downstream of a right-isosceles prism with a metal film and a liquid medium disposed on a diagonal side of the prism. Laser light passes through the first polarizer, reflects at the film, passes through the second polarizer and is detected with a shift determined by a pointer estimator to indicate the sample.