Using a high power pulse YAG laser to impinge on a graphite target in a high vacuum chamber, producing foggy-like matter of laser plasma in the space of the camber, diamond-like carbon thin films can be deposited on the Si substrate.The refractivity of the films prepared at different substrate temperature was measured by illipsometry. It was found that as the substrate temperature increased the thickness of the film decreased but the refractivity raised. This indicates a method to produce films with changeable refractivity to meet the requirement of optically enhanced transmission or reflection.