Two-Color Phase Control in Tunneling Ionization and Harmonic Generation by a Strong Laser Field and Its Third Harmonic

Ultrahigh-Order Wave Mixing in Noncollinear High Harmonic Generation

“…Early experiments confirmed that energy, momentum, and parity are preserved when high harmonics are generated in two-color fields [10]. This introduced the potential to control the high-harmonic process [11][12][13], leading to the generation of attosecond pulse trains with individual pulses separated by the laser period [14] and new approaches to isolating a single attosecond pulse [15][16][17] and generating tunable extreme ultraviolet (XUV) radiation [18]. Recently, it has been shown that weak-field control of high harmonic generation allows attosecond pulses to be measured as they are being produced in the medium [19].…”

“…Our work builds on a long history of experiments on using multiple color fields to produce high harmonics [10][11][12][13][14][15][16][17][18]. Early experiments confirmed that energy, momentum, and parity are preserved when high harmonics are generated in two-color fields [10].…”

Waveforms for optimal sub-keV high-order harmonics with synthesized two- or three-colour laser fields

“…Most efforts to enhance HHG yields with single-colour sinusoidal waves have been directed at creating favourable phase-matching conditions in the nonlinear gas medium to efficiently build up macroscopic high harmonics [4][5][6] . Alternatively, enhancement of HHG can be achieved by two-colour phase control, as first shown experimentally by Watanabe et al 7 in 1994. Since then many such measurements have been reported (Supplementary Discussion) using the fundamental 800-nm laser with its second or third harmonic where the phase between the two colours is locked but can be tuned.…”

Coherent control of high-harmonic generation using waveform-synthesized chirped laser fields

“…By coherently synthesizing the field amplitudes, the subcycle field shape (or waveform) can be changed, therefore both the ionization and the subsequent electron motion can be steered. Commonly used additional colors include the second harmonic and the third harmonic of the fundamental due to experimental convenience [14][15][16][17][18][19][20][21][22], although other colors have also been widely explored [23][24][25][26][27][28][29]. This multicolor amplitude synthesis has led to substantial progress on coherent harmonic control towards various purposes, such as extending the harmonic cutoff, enhancing the HHG yield, generating an isolated attosecond pulse, etc.…”

“…The other harmonic control technique makes use of one or more colors in addition to the fundamental [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. By coherently synthesizing the field amplitudes, the subcycle field shape (or waveform) can be changed, therefore both the ionization and the subsequent electron motion can be steered.…”