Optimal design and analysis of refractive index and thickness gradient optical films

Abstract Gradient optical films have potential applications in instrumentation, display technology, avionics and other fields, it is usually plated on the instrument lens to transmit or reflect the corresponding waveband. In order to improve the transmittance and avoid the disadvantages of uniform films, in order to change the traditional film layer arrangement, this paper proposes a graded refractive index film and a graded thickness film. Through Matlab and TFCalc software simulation, the results show that the final reflectivity curves not only have good rectangularity, but also are closer to the ideal reflectivity of 100% at the central wavelength. Among them, the reflectivity of the high-reflective film in a specific range can reach 99.4%, the reflectivity of the minus filter at 532 nm is 99.6%, in the ranges of 385 nm–490 nm and 570 nm–780 nm on both sides, the reflectivity is greater than 91,5%. This result shows that the actual application effect of the thin film designed with a gradual structure is better.