A kind of photoemissive thin films which can be exposed to or stored in the atmosphere and can be used again in a vacuum system without any activation process for laser pulse detection is presented. They are different from usual photoemissive materials, since they do not contain alkali elements. They consist of metallic oxide thin film or other material thin film embedded with metallic ultrafine particles. A main interesting material is barium oxide thin film embedded with Ag ultrafine particles. The phenomenon that photoemissive sensitivity of this kind of ultrafine particle thin film rose up under the action of laser pulses was discovered.