Broadband imaging spectrometer based on conical diffraction for extreme ultraviolet source

We demonstrate what we believe to be a novel design of an imaging spectrometer tailored for extreme ultraviolet (EUV) sources, employing uniformly spaced planar gratings. For what appears to be the first time, our approach adopts a grating-toroid-grating configuration for spectral measurements femtosecond high-harmonic EUV lasers. This spectrometer performs superior in point-to-point imaging modes and the resulting experimental setup is very simple. And because of its special structure, this spectrometer can achieve aberration-free imaging of image spots in all working wavelength ranges. The resulting experimental setup is notably straightforward, yet it delivers an optimized combination of high flux efficiency, sufficient spectral resolution, and broad spectral coverage. In this paper, a detailed analysis of the aberration of the device is studied, and a reasonable data simulation is carried out. Our findings, which harmoniously merge experiment data with theoretical simulations and analyses, meticulously delineate the origins of aberrations. This point-to-point imaging spectrometer could serve a broad spectrum of scientific research applications. It facilitates ultrafast spectroscopic and pump-probe experiments with femtosecond to picosecond precision, suitable for both foundational and applied research endeavors across diverse disciplines.