Changing the Reflectivity of a Silica Glass Surface

The superposition of two linearly polarized continuum lasers beams of different brightnesses on a silica glass surface can inhibit the reflectivity of the surface to the weaker laser radiation. We perform an experiment where the reflectance of a 532 nm probe laser incident near Brewster Angle is challenged by the optical field of a stronger coupling laser of same 532 nm wavelength. The dipoles on the glass surface get polarized, and therefore, aligned along the resultant of the two linearly polarized optical fields. These arrays of polarized dipoles reflect the incident radiation of a probe laser similar as a diffraction grating. Maxima and minima of interference appear with an angular spacing of △θ = λ/d, associated to a geometric path difference: d sin(θ) = m.λ, where d is 0.0194mm in our case. The fringes appear in a range of 5° from Brewster angle and indicate a change in the optical reflectivity of the silica surface with reduction of reflectivity at minima and enhancement of reflectivity at maxima of interference. In other words, by scanning a silica surface with a laser beam, one can find positions where the beam is retained by the surface dipoles and positions where the laser beam is sent back with a greater reflectivity. This experimental result can be used to create an optoelectronic switching device.