Laser-induced absorption in titanium oxide based gels

We report the first observation of a strong laser-induced absorption (darkening) in a new class of medium: basic undoped titanium oxide gels. The effect reveals a complex temporal behaviour: the absorption firstly appears in the UV and later extends over the visible spectral region. We show that the underlying processes are of the photochemical nature and require an integrated dose of ∼7 J/cm2. The visible darkening is reversible with the recovery time of several minutes. Unusual properties of titanium oxide gels make them interesting for potential applications in photonic devices.