Study On Scattering Characteristics Of Multilayer Optical Thin Films

The scattering problem of optical films has always been a key factor affecting the performance of optical films.The scattering loss caused by its rough surface has limited the further development and application of optical films.Even small scattering losses may cause great experimental error.Therefore,exploring the scattering characteristics of optical films is expected to provide a way to reduce surface scattering,which is imminent.This paper has carried out theoretical and experimental research on the factors affecting the surface scattering of single-layer optical films with micro-roughness and the characteristics of anti-scattering,and vector light scattering caused by multilayer optical films.The main work and results are as follows:（1）This paper explore the influence of different deposition processes on the surface roughness and scattering characteristics of single-layer optical films.The changes of the surface roughness and scattering of the single-layer Ti O₂and Si O₂films under different deposition rates,different deposition angles,different ion source energies,and different substrate roughness were investigated.The research found that the surface roughness of Ti O₂films decreases with the increase of the deposition rate until it reaches a stable value;the surface roughness of the Si O₂films shows a trend of first decrease and then increase with the increase of the deposition rate,so there is an extreme point is the optimal deposition rate.The surface roughness of a single-layer Ti O₂/Si O₂film will increase with the increase of the deposition angle,and increase with the increase of the substrate roughness,but the change of the ion source energy has little effect on it.The surface scattering of the thin film changes with the surface roughness,and the two have a positive correlation.（2）This paper explore the anti-scattering properties of single-layer optical films.In this paper,based on the theory of first-order perturbation,the anti-scattering conditions of single-layer optical films are given,and related experiments are designed based on these conditions.Ti O₂/Si O₂film,and the surface roughness of the film was adjusted to achieve the desired value.The surface scattering distribution of the film and bare substrate were measured before and after the experiment.The results show that the surface roughness,optical thickness,and refractive index of optical films are all key factors affecting optical films.For single-layer Ti O₂and Si O₂films with specific optical thickness,when the ratio of the upper and lower interfaces roughness meets the anti-scattering interval.At this time,the effect of anti-scattering can be achieved,and the closer the ratio is to the optimal value of anti-scattering,the better the effect of anti-scattering.The experimental results agree with the theoretical research.（3）This paper investigate the scattering characteristics of multilayer optical films.According to the vector scattering theory of multilayer optical films and the relationship between the bidirectional reflection distribution function and the scattering loss of the film,the correlation between the multilayer film layers is introduced into the expression of the scattering loss to study the scattering of thin film.The research found that the interface roughness of the five layers film exhibited alternating high and low in the experiment,indicating that the Ti O₂film has the function of smoothing the substrate,while the Si O₂film will roughen the surface roughness of the film;the surface scattering of the multilayer film not only interfaces with the film Roughness is related to the correlation between the roughness of the interface between the layers and the coherence of scattered light.