High-Energy Carrier-Envelope Phase-Stable Optical Waveforms Compressible to <1 fs Using Induced-Phase Modulation in Argon-Filled Hollow-Core Fiber

Abstract

Abstract:We demonstrate phase-stable, ~0.4-mJ optical waveforms based on induced-phase modulation for generating sub-fs optical pulses. Using custom-designed double-chirped mirrors and a spatial light modulator, such optical waveforms will become a versatile tool for strong-field attoscience.Ultrashort optical pulses with high energy and multi-octave bandwidth have been greatly desired for the generation of intense monocycle optical pulses. This is because those pulses are expected to be crucially important as driver pulses for efficient generation of isolated attosecond pulses with sub-100-as duration in the extreme-ultraviolet (XUV) region. However, the generation of such pulses with both high energy and multioctave bandwidth has been a very challenging subject so far. To overcome the problem, one of the most popular techniques is coherent optical waveform synthesis, which means the generation of custom-tailored, intense, fewcycle or even sub-cycle optical waveforms by coherently stitching together separate spectral portions. Currently, coherent waveform synthesis is one of the most intriguing and promising frontiers of attosecond science and strong-field physics, opening up unprecedented prospects, e.g., for precision control of strong-field interactions in atoms, molecules and solids, generation of intense isolated attosecond pulses, and attosecond pump-probe spectroscopy employing ultrashort pulses in the VIS/IR and XUV/soft-X-ray regions.Up to now, coherent waveform synthesis based on self-phase modulation (SPM) in a neon-filled hollow-core fiber (HCF) compressor allowed for the generation of sub-cycle ~300-µJ optical pulses [1]. For pursuing the synthesis of the shortest possible pulses within this scheme, the total output energy of this multi-channel synthesizer is limited to a few tens of µJs mainly by the UV channel containing the smallest pulse energy [2], thus preventing further energy upscaling to the (multi-)mJ level, which is required for many interesting applications in attosecond science. A potential solution out of this dilemma is the application of induced-phase modulation (IPM) [3] based on the interaction between two (or more) co-propagating optical pulses of different colors and relatively long pulse durations in a gas-filled HCF. The IPM technique offers control over the spectral shape by adjusting the relative intensity ratio and the relative delay between the input pulses and allows a more efficient generation of broader-band optical pulses than those produced solely by SPM. Such an IPM-based synthesizer is expected to greatly relieve the energy-scaling bottleneck in the UV region [4], and the enhanced spectral broadening of the UV region is particularly appealing for the realization of ultrahigh HHG conversion efficiencies in bright coherent tabletop high-harmonic sources.In our earlier work, we already generated transform-limited (TL) 2.6-fs, 3.6-µJ optical pulses centered at 600 nm by compensating for the chirp of the ultrabroad spectrum generated by IPM in an argon-filled HCF [3]. La...

Coherent pulse synthesis: towards sub-cycle optical waveforms

“…The IPM technique offers control over the spectral shape by adjusting the relative intensity ratio and the relative delay between the input pulses and allows a more efficient generation of ultrabroadband optical pulses than those produced solely by SPM. A synthesizer in which the broadband pulses are obtained with IPM instead of SPM only is expected to greatly relieve the energy‐scaling bottleneck due to the weak UV region , and the enhanced spectral broadening of the UV region is particularly appealing for the realization of ultrahigh‐harmonic generation conversion efficiencies in bright tabletop HHG sources. An IPM‐based optical waveform synthesizer powered by a CEP‐stabilized Ti:sapphire chirped‐pulse amplifier (CPA) system is shown in Fig.…”

Toward Waveform Nonlinear Optics Using Multimillijoule Sub-Cycle Waveform Synthesizers

“…In this section, we discuss our recent experimental progress toward an above-millijoule IPM waveform synthesizer [74], [75] driven by a CEP-stabilized Ti:sapphire chirped-pulse amplification (CPA) system. Using a neon-filled fused-silica HCF, we obtained a 1.72-mJ CEP-locked supercontinuum spanning the range 340-950 nm, which is straightforwardly compressible to terawatt attosecond optical waveforms.…”