The noise caused by internal mechanical dissipation in high refractive index amorphous thin films in dielectric mirrors is an important limitation for gravitational wave detection. The objective of this study is to decrease this noise spectral density, which is linearly dependent on such dissipation and characterized by the loss angle of Young’s modulus, by adding zirconia to titania-doped tantala, from which the current mirrors for gravitational wave detection are made. The purpose of adding zirconia is to raise the crystallization temperature, which allows the material to be more relaxed by raising the practical annealing temperature. The Ta, Ti, and Zr oxides are deposited by reactive magnetron sputtering in an ${\mathrm{Ar}:\mathrm{O}}_2$ atmosphere using radio frequency and high power impulse plasma excitation. We show that, thanks to zirconia, the crystallization temperature rises by more than $150{}^{°}$C, which allows one to obtain a loss angle of $2.5\times {10}^{-4}$, that is, a decrease by a factor of 1.5 compared to the current mirror high-index layers. However, due to a difference in the coefficient of thermal expansion between the thin film and the silica substrate, cracks appear at high annealing temperature. In response, a silica capping layer is applied to increase the temperature of crack formation by $100{}^{°}$C.

中文翻译：

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用于低机械损耗布拉格反射镜的氧化锆-二氧化钛掺杂的钽光学涂层

介电镜中高折射率非晶薄膜的内部机械耗散引起的噪声是引力波检测的一个重要限制。本研究的目的是通过向掺杂二氧化钛的钽中添加氧化锆来降低这种噪声频谱密度，该密度与这种耗散呈线性相关，并以杨氏模量的损耗角为特征，用于引力波检测的电流镜是由氧化锆制成的. 添加氧化锆的目的是提高结晶温度，通过提高实际退火温度，使材料更加松弛。Ta、Ti 和 Zr 氧化物通过反应磁控溅射沉积在${\mathrm{氩气}：\mathrm{哦}}_2$大气使用射频和高功率脉冲等离子体激发。我们表明，由于氧化锆，结晶温度上升超过$150{}^{°}$C，它允许获得损失角为 $2.5\times {10}^{-4}$，即与电流镜高折射率层相比减少了 1.5 倍。然而，由于薄膜和二氧化硅基板之间的热膨胀系数不同，在高退火温度下会出现裂纹。作为响应，应用二氧化硅覆盖层以通过以下方式提高裂纹形成的温度$100{}^{°}$C。