Thermal shock effect on diamond-like carbon thin films induced by pulsed-laser

When high power laser irradiates the infrared imaging system, the system will be injured or destroyed. The damage to the systems varies for different laser wavelengths. The infrared windows are generally coated with diamond-like carbon(DLC) thin films to protect itself and improve the permeation rate. When the incident laser's wavelength lies outside the infrared system response wave band, laser destroys the DLC films firstly. The DLC films' damage mechanism induced by pulsed laser is studied with the 1.06 μm laser. The thermal shock effect model of DLC films is proposed. The temperature and stress distributions are deduced through solving the thermal conduction equation and stress-balance equation. The theoretical analysis shows that thermal stress fracture dominants in the damage mechanism. When the irradiation energy density is E₀ = 100 mJ · cm^-2, the pressure on the surface of DLC films at about 40 μm from the center of laser facula exceeds the rupture intensity, the film will break and peel off. The theoretical analysis matches the experimental results basically, and the correctness of the thermal shock effect model is confirmed.