making light waves visible: attosecond sampling of the field of light
The electric field of light, even if precisely controlled even if precisely controlled
, must be measured before it can be used for steering the motion of electrons inside atoms, molecules, or solids. Conventional pulse characterisation techniques are able to determine how the amplitude (dashed line) and – possibly – the oscillation period varies across the pulse. However, the waving itself – whether having a single or a couple of main peaks (single-peaked vs. double-peaked), making a crucial difference for electron steering has remained hidden. A synchronized attosecond electron bunch resolves the problem.
, must be measured before it can be used for steering the motion of electrons inside atoms, molecules, or solids. Conventional pulse characterisation techniques are able to determine how the amplitude (dashed line) and – possibly – the oscillation period varies across the pulse. However, the waving itself – whether having a single or a couple of main peaks (single-peaked vs. double-peaked), making a crucial difference for electron steering has remained hidden. A synchronized attosecond electron bunch resolves the problem.Electron emission induced by an attosecond extreme ultraviolet pulse in the attosecond transient recorder is confined to a small fraction of the wave period of the streaking light field. Hence, if launched into the light field to be measured, these electrons suffer a well-defined energy shift that depends on their timing with respect to the waves in the light pulse. Scanning this attosecond electron probe across the light pulse results in electron energies being shifted up and down according to the oscillations of the light field, as shown in slow-motion replay above. To make these oscillations perceivable, time has been dilated by a factor of ~ 1 000 000 000 000 000. The device performing this measurement can be regarded as an oscilloscope with a resolution reaching the petahertz (10^{15} oscillations per second) frontier.
in the attosecond transient recorder is confined to a small fraction of the wave period of the streaking light field. Hence, if launched into the light field to be measured, these electrons suffer a well-defined energy shift that depends on their timing with respect to the waves in the light pulse. Scanning this attosecond electron probe across the light pulse results in electron energies being shifted up and down according to the oscillations of the light field, as shown in slow-motion replay above. To make these oscillations perceivable, time has been dilated by a factor of ~ 1 000 000 000 000 000. The device performing this measurement can be regarded as an oscilloscope with a resolution reaching the petahertz (10^{15} oscillations per second) frontier.further reading
- The first petahertz oscillogramm of a light wave was recorded by Goulielmakis et al.:
Direct measurement of light waves; E. Goulielmakis, M. Uiberacker, R. Kienberger, A. Baltuska, V. Yakovlev, A. Scrinzi, Th. Westerwalbesloh, U. Kleineberg, U. Heinzmann, M. Drescher, F. Krausz; Science 305, 1267 (2004). - 3.3-fs infrared light pulses have been visualized by Goulielmakis et al.:
Single-Cycle Nonlinear Optics E. Goulielmakis, M. Schultze, M. Hofstetter, V. S. Yakovlev, J. Gagnon, M. Uiberacker, A. L. Aquila, E. M. Gullikson, D. T. Attwood, R. Kienberger, F. Krausz, U. Kleineberg; Science 320, 1614 (2008).