Shanghai Optics and Machinery Institute has made progress in the development of picosecond reflectors based on composite materials

Recently, the High Power Laser Element Technology and Engineering Department of the Shanghai Institute of Optics and Mechanics, Chinese Academy of Sciences, has made progress in the research of picosecond reflectors based on composite materials. The relevant research results are titled "Hybrid material based mirror coatings for picosecond laser applications" and published in Optics and Laser Technology.

Picosecond pulse lasers are often used in high-energy density physics basic research. As a key component of picosecond laser systems, the laser damage threshold of the reflector directly affects the output energy of the picosecond laser system. Traditional picosecond laser reflectors use hafnium oxide and silicon oxide as high and low refractive index materials, respectively. In recent years, composite materials, including nano layers and mixtures, have received widespread attention in improving the laser damage threshold of thin film components. Studying the picosecond reflectors of composite materials and their laser damage characteristics under different pulse widths of laser irradiation has certain practical application value.

Figure 1. (a) AFM microscopy images and RMS roughness of different mirrors (b) probability distribution of laser induced damage (8ps, 1053 nm)

Figure 2. Probability distribution of laser induced damage with different pulse widths (a) 0.5 ps (b) 1 ps and (c) 3 ps (d) Changes in laser damage threshold with laser pulse width

Researchers used electron beam evaporation technology to prepare four types of composite materials, including hafnium oxide/alumina nano layers, hafnium oxide/silicon oxide nano layers, hafnium oxide alumina mixtures, and hafnium oxide silicon oxide mixtures. Compared with single hafnium oxide materials, composite materials can inhibit crystallization and reduce surface roughness. Four types of reflective mirrors with operating wavelengths at 1053 nm were prepared using the above-mentioned composite materials and silicon oxide materials as high and low refractive index materials. The damage test results of the mirror under laser irradiation with different pulse widths (0.5 ps, 1 ps, 3 ps, and 8 ps) show that compared with the picosecond mirror using hafnium oxide as a high refractive index material, the picosecond mirror using composite materials as a high refractive index material exhibits a higher excitation damage threshold. Within the laser pulse range studied in this article, the initial laser damage mechanism of the reflector begins to change around 3 ps. This achievement is of great significance for improving the performance of optical thin film components such as picosecond laser reflectors.

Source: Shanghai Institute of Optics and Mechanics