Opening a new route to multiport coherent XUV sources via intracavity high-order harmonic generation

High-order harmonic generation (HHG) is currently utilized for developing compact table-top radiation sources to provide highly coherent extreme ultraviolet (XUV) and soft X-ray pulses; however, the low repetition rate of fundamental lasers, which is typically in the multi-kHz range, restricts the area of application for such HHG-based radiation sources. Here, we demonstrate a novel method for realizing a MHz-repetition-rate coherent XUV light source by utilizing intracavity HHG in a mode-locked oscillator with an Yb:YAG thin disk laser medium and a 100-m-long ring cavity. We have successfully implemented HHG by introducing two different rare gases into two separate foci and picking up each HH beam. Owing to the two different HH beams generated from one cavity, this XUV light source will open a new route to performing a time-resolved measurement with an XUV-pump and XUV-probe scheme at a MHz-repetition rate with a femtosecond resolution. Extreme ultraviolet: generating coherent pulses inside a laser A compact table-top laser system developed by researchers in Japan can generate extreme ultraviolet radiation (XUV) for ultrafast spectroscopy. Coherent XUV pulses are used to accurately measure data on electronic transitions in atoms and molecules, however they can usually only be generated via synchrotron radiation from large particle accelerators. A possible route to generating XUV on a smaller lab scale is to direct high-order harmonic pulses from a femtosecond laser onto a gas. Katsumi Midorikawa at the RIKEN Center for Advanced Photonics in Wako and co-workers have developed a novel method where the gas targets are actually placed inside the laser cavity. By using two different gases, they can simultaneously generate an XUV pump and a probe, opening a route to very accurate timing of atomic measurements, perhaps resolving events as short as a few femtoseconds.