Coherent control of boosted terahertz radiation from air plasma pumped by a femtosecond three-color sawtooth field

Abstract

We report on the coherent control of boosted ultrashort terahertz pulse emitted from air plasma pumped by a femtosecond sawtooth pulse composed of three optical harmonic fields. With an in-line optical setup, the relative phases between the three optical components of the pump pulse can be varied independently with attosecond precision without the complexity of external phase stabilization. We observe that the amplitude of the terahertz emission pumped by the phase-optimized sawtooth wave is enhanced by 1.8 times compared to the widely used two-color scheme. Moreover, by manipulating the relative phases between the three colors at attosecond precision, coherent control of the azimuthal angle, ellipticity, and polarity of THz radiation is achieved. A local current model reproduces well the coherent control observations.

Coherently controlled ionization of gases by three-color femtosecond laser pulses

“…This period doubling originates from breaking the mirror symmetry of the two color fields containing only the fundamental and second harmonics due to the addition of the third harmonic. This effect is very similar to the period doubling that occurs in the phase dependence of the amplitude of THz radiation generated by the three-color pulse [18].…”

“…Moreover, it has been demonstrated that ionization of molecules can be enhanced and coherently controlled with two-color laser pulses composed of a fundamental frequency with either its second or third harmonics [13][14][15]. Recently, it has been reported that a laser field composed of 3 or more colors can be even more beneficial [16][17][18]. Compared to two-color laser field excitation, the three-color scheme provides extra control parameters and has proven its versatility in the selection of single harmonic radiation from the comb of high-order harmonics [19], in the coherent control of the polarization and chirality of THz pulses produced from air plasma [18], and in the generation of supercontinuum ranging from mid-infrared to ultraviolet [17,20].…”

“…Recently, it has been reported that a laser field composed of 3 or more colors can be even more beneficial [16][17][18]. Compared to two-color laser field excitation, the three-color scheme provides extra control parameters and has proven its versatility in the selection of single harmonic radiation from the comb of high-order harmonics [19], in the coherent control of the polarization and chirality of THz pulses produced from air plasma [18], and in the generation of supercontinuum ranging from mid-infrared to ultraviolet [17,20]. However, the fundamental process of molecule ionization by a phase-controlled three-color laser field has remained largely unexplored.…”

Multichromatic Polarization-Controlled Pulse Sequences for Coherent Control of Multiphoton Ionization

“…As a first step towards more complex pulses, we consider a trichromatic application. Trichromatic fields offer enhanced possibilities for ultrafast applications such as multicolor spectroscopy [214], strong-field physics [215,216], the generation of terahertz radiation [217,218] and HHG [219]. Further examples of trichromatic pulse sequences are illustrated in Figure 12.…”

Analysis of Combination Frequencies Arising from the Ionization of Gases by Multicolor Femtosecond Pulses

“…This can be done using the frequency tuning of the ionizing pulse components in optical parametric generators [11][12][13]. Recently, the possibility of using multi-color (three or more) pulses instead of traditional two-color ionizing pulses has been increasingly investigated [13][14][15][16]. The solution of optimization problems for such systems is complicated by the fact that the extremely nonlinear nature of ionization-induced multiwave mixing (IMWM) manifests itself in a strong interdependence of the optimal values of each pulse parameter on the values of all others [14,[17][18][19].…”