Optical bistability induced by Gouy phase shift

Optical bistability in a passive ring cavity with no designed nonlinear materials is experimentally observed in the near-infrared region. The nonlinear material that induces the optical bistability is considered to be water molecules in atmosphere. In the model calculation, it is found that the optical bistability is induced by transversal distribution of optical power-dependent refractive index of water in the Gaussian beam, which causes the power-dependent Gouy phase shift in the cavity. The model calculation agrees qualitatively with the experimental results. This result suggests that the Gouy phase shift has an effect on cavity-enhanced molecular spectroscopy.