Multi-field simulation of thin film filter with CW laser oblique incidence

We have designed two kinds of narrow-band thin film filters with Ta₂O₅/SiO₂. In order to use them as laser beam combining elements, the multi-field simulation of two kinds of filters under CW (continuous wave) laser oblique incidence is carried out. After comparing the electric field, thermal field and stress field of the two kinds of film profiles during transmission and reflection, the change rules of each field under transmission and reflection conditions are obtained. For different film structures, the electric field strength, temperature and stress in the film are higher than the reflection's. After that, the multi-field results of the same design is analyzed and the internal relations among the fields are obtained. The higher the electric field strength is, the more the temperature rise is and the greater the thermal stress is. Finally, the temperature rise of the filters with different focusing effects is simulated when the CW laser is oblique incident. We found that with the enhancement of focusing effect, the overall temperature rise increases, otherwise the temperature rise decreases.