Broadband stable depolarizing beam splitter with high splitting ratio in 780-nm band

To ensure stable output of the 780 nm band laser with a large splitting ratio, a high splitting ratio depolarizing beam splitter was designed and fabricated in this paper. Initially, the double-sided depolarizing film system was designed and simulated. Subsequently, the sample was fabricated using ion beam assisted deposition. The film structure of the sample was analyzed using a TEM, and its transmittance spectrum was measured with a spectrophotometer. The spectral results showed that in the working band wider than 60 nm, the transmittance of the beam splitter was close to 98%, and the transmittance deviation is less than 0.3%. Finally, experiments were conducted to evaluate the performance of the beam splitter. The depolarizing beam splitter presented in this paper demonstrates excellent depolarization performance and is suitable for direct application in precision measurement fields such as optical test metrology and quantum sensing detection.