The generation and utilisation of half-cycle cut-offs in high harmonic spectra

• Published in: Laser & photonics reviews Vol. 4; no. 6; pp. 697 - 719
• Main Authors: Chipperfield, L.E., Robinson, J.S., Knight, P.L., Marangos, J.P., Tisch, J.W.G.
• Format: Journal Article
• Language: English
• Published: Berlin WILEY-VCH Verlag 01.11.2010; WILEY‐VCH Verlag; Wiley-VCH
• Subjects: attosecond; Attosecond pulses; carrier-envelope phase; CEP; Cut-off; Driving; Exact sciences and technology; few-cycle pulses; Frequency conversion ; harmonic generation, including high-order harmonic generation; Fundamental areas of phenomenology (including applications); Harmonics; HHG; High-order harmonic generation; Lasers; Nonlinear optics; Optics; phase matching; Physics; Spectra; Spectral emissivity; Ultrafast processes; optical pulse generation and pulse compression; Waveforms; as range; Optical phase matching; HHG; 42.65.Ky; few-cycle pulses; Far field; Optical harmonic generation; phase matching; CEP; attosecond; Ultrashort pulse; High-order harmonic generation; 42.65.Re; Optical frequency conversion; 32.80.Rm; Nonlinear optics; Higher harmonic; carrier-envelope phase
• ISSN: 1863-8880; 1863-8899; 1863-8899
• DOI: 10.1002/lpor.200900028

High‐order harmonic spectra are composed of a coherent sum of half‐cycle emissions, the cut‐off energy of which depend sensitively on different sub‐cycle portions of the driving laser field. By selecting the correct focal geometry the half‐cycle cut‐off emissions can be preferentially selected over the lower energy plateau emissions through phase matching, such that they form macroscopic half‐cycle cut‐off features in the far‐field spectrum. The energy of these macroscopic half‐cycle cut‐offs can then be used to retrieve the waveform of the driving laser field. The processes through which these macroscopic half‐cycle cut‐offs are formed and their applications, both for measuring the laser waveform and the generation of wavelength tunable isolated attosecond pulses, are reviewed in detail. Controlling electron dynamics within atomic and molecular systems typically evolve attosecond timescales, so that their illumination requieres a probe that can be controlled with comparable temporal resolution, i.e. sub‐cycle pulses. High‐order harmonic spectra are composed of a coherent sum of half‐cycle emissions, the cut‐off energy of which depend sensitively on different sub‐cycle portions of the driving laser field. The energy of these macroscopic half‐cycle cut‐offs can be used to retrieve the waveform of the driving laser field.