Strongly enhanced pair production in combined high- and low-frequency laser fields

Production of electron-positron pairs by a high-energy probe photon propagating through a high-intensity laser field is considered in the nonperturbative interaction regime. The laser field consists of a strong low-frequency and a weak high-frequency component. While for each component alone photoproduction of pairs is strongly suppressed, we show that their combination can largely amplify the pair production probability by facilitating to bridge the energetic barrier of the process. Our predictions can be tested by utilizing presently available high-intensity laser devices.

Figure 1

Rate for pair production by a high-energy probe photon with ${\omega }_{\gamma }\approx 0.9487m$ counterpropagating a bifrequent laser beam with ${\omega }_1={\omega }_{\gamma }$ (such that $\Delta =0.1$), ${\xi }_1=2\times {10}^{-3}$, and ${\omega }_2=0.1m$, as a function of the inverse field intensity parameter ${\xi }_2$ (black squares). The red circles and blue crosses show the respective contributions to the rate from absorption of zero and one assisting ${\omega }_1$ photon, as indicated. The lines are exponential fit functions to the data (see text for further details). Note that $m=7.76\times {10}^{20}$ s${}^{-1}$ in SI units.

Figure 2

Dependence of the pair production rate on the gap parameter at ${\omega }_1={\omega }_{\gamma }=m\sqrt{1-\Delta }$, ${\xi }_1=2\times {10}^{-3}$, ${\omega }_2=0.1m$, and ${\xi }_2=0.7$ (black squares). The red circles, blue crosses, and green asterisks show the respective contributions to the rate from absorption of zero, one, and two assisting ${\omega }_1$ photons, as indicated. The blue line is a fit function of the form suggested by Eq. (14).

Figure 3

Rate for pair production by a high-energy probe photon with ${\omega }_{\gamma }\approx 0.9487m$ counterpropagating a bifrequent laser beam with ${\omega }_1={\omega }_{\gamma }/2$, ${\xi }_1=4.5\times {10}^{-2}$, and ${\omega }_2=0.05m$, as a function of the inverse field intensity parameter ${\xi }_2$ (black squares). The blue crosses, green asterisks, and pink daggers show the contributions to the rate from absorption of one, two, and three assisting ${\omega }_1$ photons, respectively. The red circles show the production rate in the absence of the high-frequency laser mode. The lines are exponential fit functions to the data.