Influence of porosity on laser damage threshold of sol–gel ZrO2 and SiO2 monolayer films

Monolayer ZrO2 sol–gel and physical vapor deposition (PVD) films were prepared by spin method and electron beam evaporation method, respectively. Monolayer sol–gel SiO2 films were prepared with the dip-coating method from acid and base catalyzed SiO2 sols, respectively. Some of the SiO2 base films were subsequently treated in saturated ammonia gas for 20 h. The laser induced damage threshold (LIDT) of each film was measured. Properties of the films were analyzed by using Stanford photo-thermal solutions (SPTSs), ellipsometer, atomic force microscopy (AFM) and optical microscopy. The experimental results showed that porous ratio is an essential factor to decide the LIDT for sol–gel films, which benefits the pressure exerted on the film or substrate by the moving particle to dissipate. The films with lower thermal absorption and higher porous ratio have higher LIDT.