Spatiotemporal control of laser intensity

Controlling the velocity of a femtosecond laser pulse using refractive lenses

“…1(c), or even negative depending on the magnitude of the chirp (i.e. backwards propagation, which has already been demonstrated experimentally [10,12]). The expected velocity of the intensity peak was derived in Saint-Marie et al [9], and is reproduced here:…”

“…The combination of the longitudinal separation of the frequencies in focus and a frequencyvarying arrival time, described by the group delay dispersion (GDD) φ 2 , produces the flying focus effect where within the extended focal region the intensity peak of the pulse can travel at velocities radically different from c [9][10][11]. This concept is shown schematically in Figs.…”

“…2(a) uses a diffractive focusing element that inherently focuses different wavelengths to different longitudinal positions. In this case, the effective coupling parameter α is given by α = 1/2cf , which produces the relationship v ff = c/(1 + ω 0 φ 2 c/f ) for the flying focus velocity [10] when the fixed α is inserted in Eq. (1).…”

“…by introducing correlations between the temporal and spatial degrees of freedom of the electric field that are non-separable [5][6][7][8]. Here we discuss the so-called flying focus effect whereby the velocity of the light intensity peak formed within the focal region of a broadband laser pulse can be arbitrarily different than the speed of light via very simple spatio-temporal shaping [9,10]. This recently identified effect has many potential scientific applications such as ionization waves of arbitrary velocity [11][12][13], Raman amplification in a plasma [14], particle acceleration [15], and photon acceleration [16].…”

“…This recently identified effect has many potential scientific applications such as ionization waves of arbitrary velocity [11][12][13], Raman amplification in a plasma [14], particle acceleration [15], and photon acceleration [16]. The flying focus (also referred to as the "sliding focus") has been demonstrated on a laser system with sub-picosecond duration [10] using a diffractive lens to induce spatio-temporal couplings, a scheme well-suited to the rather narrow spectral width of such a laser. We present here an implementation of this effect more appropriate for femtosecond laser beams, which exploits the chromatic properties of a special lens doublet rather than those of a diffractive lens.…”