The optical constants for the absorbing layer material， satisfying high efficiency of the photon-to-heat conversion of a four-layer structure from ultraviolet to near-infrared wavelength range， are theoretically studied. By employing the effective medium approximation （EMA） model， the measured optical properties of the composite materials （cermet） show in great agreement with that of the simulated ones. Furthermore， a four-layer film structure with high photon-to-heat conversion efficiency using Ti-MgF₂ cermet as the absorption layer is proposed to have a high absorptance of about 95.1% achieved in the wavelength range of 300~1 600 nm. The research results provide a new method to realize high-efficiency photon-to-heat conversion devices and show excellent application prospects.