A research group led by Assistant Professor Takato Inoue and Professor Satoshi Matsuyama (concurrently Assistant Professor at the Graduate School of Engineering, the University of Osaka) from the Graduate School of Engineering at Nagoya University, along with Group Director Makina Yabashi and Team Leader Yoshiki Kohmura from the RIKEN SPring-8 Center, has successfully fabricated a deformable mirror composed of only one thin piezoelectric single crystal wafer, achieving the world's first success in 3400-fold beam size variation. Their results were published in Scientific Reports.
(a) A photograph of the mirror substrate comparison with a Japanese 100-yen coin.
(b) Deformation mechanism.
(c) Variable-beam-size optical system.
Provided by Nagoya University
Deformable mirrors are utilized in various fields and have recently attracted attention as variable optical parameter lenses in X-ray focusing systems. While various deformable mirrors have been developed, they had insufficient amounts of deformation. To increase deformation amounts, the mirror needs to be made as thin as possible, but conventional mirrors had structural limitations because bonding of different materials was essential.
(a) Relationship between applied voltage and mirror deformation.
(b) Captured X-ray beam shape in convergence mode and (c) in divergence mode.
Provided by Nagoya University
The research group therefore focused on the polarization inversion characteristics of lithium niobate (LN), a piezoelectric single crystal. When LN is heated at high temperatures of approximately 1000℃, its polarization structure partially changes. By utilizing this characteristic, a bimorph structure can be formed without bonding, making it possible to reduce mirror thickness to the utmost limit.
In practice, the group developed a mirror with a thickness of only 0.5 millimeters and succeeded in 3400-fold beam size variation by controlling its shape.
This enables multifunctional X-ray analysis that can not only change the field of view and resolution of X-ray analysis by significantly altering optical parameters such as beam size but also switch between analysis methods. Furthermore, this mirror can be made even thinner, and calculations show that if thinned to the order of 0.01 millimeters, the deformation amount would increase by approximately another 100-fold; this is expected to be useful across a wide range of wavelengths including not only the X-ray region but also visible light.
Journal Information
Publication: Scientific Reports
Title: Ultrathin monolithic bimorph mirror using polarization-inverted lithium niobate wafer
DOI: 10.1038/s41598-025-05019-8
This article has been translated by JST with permission from The Science News Ltd. (https://sci-news.co.jp/). Unauthorized reproduction of the article and photographs is prohibited.