Sub-Cycle Pulse Compression Origins from Yb:KGW Amplifier

Lasers based on Ti:Sapphire crystals have long been at the forefront of cutting-edge light technology, enabling the generation of single, sub-cycle, and optical attosecond pulses in the visible and adjacent ranges of the electromagnetic spectrum. Such pulses have played a pivotal role in the development of strong field physics in atoms, molecules, and solids as well as the advancement of attosecond science [1]. Developments of the Yb:KGW technology over the past decade have opened the promise for a new generation of ultrafast lasers with scalable energy and repetition rates, which are soon anticipated to take the lead in advancing ultrafast science to the next level. Nevertheless, compression of their pulses to the single-cycle or below has remained beyond reach. Key reasons include the relatively long duration of these pulses (~170 fs) delivered by these systems compared to their Ti:Sapphire counter parts, and the decreased nonlinearity of gas media at infrared carrier frequencies. As a result, the compression factor required (>70) for achieving the single and even sub-cycle regime is challenging. Efforts over the last decade using nonlinear methods have made significant steps towards the ultrafast compression of these pulses generated by Yb:KGW amplifiers [2]. Utilization of cascade hollow-core fiber modules allowed further compression to pulse shorter than two cycles of their carrier frequency [3].