We present evidence of persistent dichroism in a monolayer which consists of azosilane molecules self-assembled on a quartz glass slide. This dichroism is shown to depend on the irradiation time. Furthermore, it could be both written and erased by irradiation with light of an appropriate wavelength. In addition, the sign of this dichroism can be inverted by choosing the appropriate polarization of the irradiating light, thus exhibiting a "smart communication" between the photochromic layer and the light polarization.