Yoshihito Tanaka

Tapered undulators are designed to generate broadband, chirped radiation for advanced synchrotron light sources. However, the complete electric-field waveform of the radiation has never been directly measured. Here, we report the first, to the best of our knowledge, direct characterization of a chirped wavepacket generated from a tapered undulator using spectral phase interferometry for direct electric-field reconstruction (SPIDER). The retrieved spectral phase reveals a distinct linear chirp, and its magnitude shows essential agreement with theoretical predictions. This work provides the first experimental validation of the chirped waveform generated from an undulator, enabling advanced temporal control of next-generation light sources.

Objective lenses are frequently employed in state-of-the-art ultrafast time-resolved microscopy techniques. While it enables tight spatial focusing, its dispersion causes a longer optical pulse duration. Since an objective lens is a combination of different lens materials, finding its correct dispersion can be challenging. In this paper, we propose a dispersion measurement method for an objective lens using white light interferometry. Our proposed method enables the experimental determination of the lens dispersion and improves the temporal resolution of ultrafast time-resolved microscopy techniques.