Development of highly accurate figure measurement method using high order harmonic generation source

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K18821
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Research Field: Mechanics of materials, Production engineering, Design engineering, and related fields
• Research Institution: The University of Tokyo
• Principal Investigator: Mimura Hidekazu 東京大学, 大学院工学系研究科(工学部), 准教授 (30362651)
• Project Period (FY): 2017-06-30 – 2020-03-31
• Keywords: 精密計測 / 位相回復法

Outline of Final Research Achievements

In precise fabrication of products, the final accuracy is determined by the measurement method. As a method of evaluating surfaces of mirrors and lenses, various methods using light have been proposed and developed. Interferometry measures the surfaces by determining the phase information of the light. The measurement accuracy can be improved by shortening the wavelength.
In this study, we proposed the use of a high order harmonic generation (HHG) source to evaluate optical surfaces, because this light source is cost-effective and compact. In this study, we developed the phase retrieval method specialized for this source and succeeded in the wavefront measurement of a HHG beam focused by a precise mirror.

Free Research Field

超精密加工、Ｘ線光学

Academic Significance and Societal Importance of the Research Achievements

表面形状のナノ精度での評価は光を用いて行われている。波長の短いＸ線を用いれば測定精度の大幅な向上が期待できる。本研究では、高次高調波と呼ばれるコヒーレントな軟Ｘ線光源の利用を提案している。この光源は実験室ベースの小型の光源であり、将来的には汎用的な利用が可能になる。本研究では高次高調波を回転楕円ミラーにより集光し、その集光ビーむの波面誤差の計測に成功した。波長は10nmレベルであり、1/10程度の波面誤差精度であったとしても1nmレベルの精度を有しており、今後の超精密形状計測への利用が期待できる。