Shanghai Institute of Optics and Mechanics has made new progress in the research on the stability of space gamma ray radiation of laser films

Recently, the Thin Film Optics Laboratory of Shanghai Institute of Optics and Precision Machinery, Chinese Academy of Sciences, cooperated with the Italian National Bureau of New Technology, Energy and Sustainable Economic Development to make new progress in the study of the spatial gamma ray radiation stability of laser films, providing data support for the development of radiation resistant space optical elements, The relevant research results were published in Optical Materials under the title of Laser induced damage of 1064 nm multilayer antiflaming coatings after exposure to gamma rays.

With the increasing demand for space technology, satellite and aircraft detection technology, space lasers are used more and more widely. In the development of space laser towards long life, high energy and high power, thin film element is one of the weakest links in optical system, and its reliability and stability are crucial to space laser system. The harsh high-energy radiation environment in space makes the reliability and laser damage performance of thin film components for space applications face severe challenges, and may also cause increased absorption loss of thin films. In addition, once the film in orbit is damaged, it cannot be repaired or replaced. Therefore, it is necessary to conduct a systematic study on the space radiation damage of laser film.

The research team conducted gamma ray radiation experiments on 1064nm multilayer antireflection films deposited by different processes. The total gamma ray dose is equivalent to 5-8 years of radiation dose in low earth orbit (LEO). By studying the optical properties, structural composition and chemical composition of the films before and after radiation, the types of defects generated in the films by gamma ray radiation and the distribution of radiation defects in different layers of multilayer films were analyzed. The research shows that gamma radiation will not change the structure of the film, but the defects such as oxygen vacancy generated by radiation will reduce the transmittance of the film in the ultraviolet band, and also increase the absorption loss of the film, leaving a hidden danger for the application of the film in high power laser systems. The damage probability of the films irradiated by gamma ray is greatly increased, and the damage threshold is also significantly reduced. The films deposited by different processes show different spatial stability, and the films with denser structure have higher radiation stability. The research results are helpful to improve the space radiation stability of laser thin films from the perspective of technology and design, and to expand the wide application of thin film materials in space environment.

Relevant work has been supported by the key projects of international scientific and technological innovation cooperation between the Chinese and Italian governments, the National Natural Science Foundation of China, and the Youth Innovation Promotion Association of the Chinese Academy of Sciences.

Fig. 1 Transmission curve of 1064nm multilayer antireflection film before and after gamma ray radiation

Fig. 2 Atomic percentage and 1064nm weak absorption of the film before and after gamma ray radiation

Source: Shanghai Institute of Optics and Precision Machinery, Chinese Academy of Sciences