Time and OAM-resolved Pump-probe Measurement with Ultrawide Temporal Dynamic Range using Dual-comb Asynchronous Optical Sampling Technique

In application of optical frequency combs, dual-comb asynchronous optical sampling (ASOPS) technique is one of the attractive utilizations [1]. ASOPS utilizes two ultrashort pulse lasers, whose repetition frequencies are controlled to be slightly different from each other. When the two combs have asynchronous repetition frequencies, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$f_{\text{rep}}$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$f_{\text{rep}}+\Delta f_{\text{rep}}$</tex>, the relative time delay between the two pulse trains is automatically swept. The scan is rapidly repeated, and time-resolved measurements with high stability, rapidity, and a wide temporal dynamic range are achieved. Meanwhile, as one of the new applicability of optical frequency combs, we have recently been promoting dual-comb technology extended towards OAM (orbital angular momentum) vortex light research [2], [3]. The DCS has been extended to the transverse dimension far beyond the conventional application range. In this study, we demonstrate time and OAM-resolved pump-probe measurement based on the dual-comb ASOPS technique. We utilize one comb source as an excitation light and the other as an OAM probe light. Then, transient changes of OAM-dependent photo-excited phenomena is measured by the ASOPS pump-probe method with the ultrawide temporal dynamic range.