Electron Emission from Metal Surfaces by Ultrashort Pulses: Determination of the Carrier-Envelope Phase

The phase $\phi$ of the field oscillations with respect to the peak of a laser pulse influences the light field evolution as the pulse length becomes comparable to the wave cycle and, hence, affects the interaction of intense few-cycle pulses with matter. We theoretically investigate photoelectron emission induced by an intense, few-cycle laser pulse from a metal surface (jellium) within the framework of time-dependent density functional theory and find a pronounced $\phi$ dependence of the photocurrent. Our results reveal a promising route to measuring $\phi$ of few-cycle light pulses ($\tau <6\mathrm{f}\mathrm{s}$ at $\lambda =0.8\mu \mathrm{m}$) at moderate intensity levels ($I_p\approx {10}^{12}\mathrm{W}/{\mathrm{c}\mathrm{m}}^2$) using a solid-state device.

Figure 1

Dependence of the photoemission on maximum field strength $F_0$ of the laser pulse for modified jellia with different density ($r_s=1.5$, 3) and work function ($W=5.1\mathrm{e}\mathrm{V}$, 2.7 eV). Inset: exponent $x$ of $I_{\mathrm{P}\mathrm{E}}\propto F_0^x$ as a function of $W/\omega$.

Figure 2

Time-resolved electron emission for different carrier-envelope phase $\phi$ and peak field strength of (a) $F_0=0.05$ ($\gamma <1$) and (b) $F_0=0.007$ ($\gamma >1$). Dotted lines indicate the envelope function of the laser pulse with $\tau =5\mathrm{f}\mathrm{s}$. Note the difference in scale in plots (a) and (b).

Figure 3

Variation of the time-integrated photoemission with the absolute phase and the maximum field strength $F_0$ of the laser pulse. Solid symbols: Same laser parameters as in Fig. 2; open symbols: $F_0=0.007\mathrm{a}.\mathrm{u}.$, $\tau =4\mathrm{f}\mathrm{s}$. The dashed line shows the photoemission when a long range image tail ($-1/4z$) is added.