We present a new technique to measure electric fields over a 1 PHz bandwidth spanning the infrared to ultraviolet with sub-femtosecond temporal resolution via the sub-cycle control of injected charge carriers in dielectric media. The fidelity of the reconstructed electric fields are benchmarked against attosecond streaking and electro-optic sampling and provide detailed information about the temporal evolution of the charge carrier density in materials exposed to strong laser fields. The resulting optoelectronic technique allows for many methods of attosecond physics to be applied to a compact, table-top measurement, without necessitating the generation of attosecond XUV pulses.
In the measurement device, a pair of metal electrodes separated by a small gap are deposited on the
surface of a dielectric. The size of the gap is adjusted to the focal spot of the laser. CEP stable few cycle laser pulses with central wavelength around 780nm are focused in the gap between electrodes to promote carriers from the valence band into the conduction band. Injected carriers are then spatially separated by the laser field being detected, creating an electric dipole. The screening effect from the electrodes generates a measurable current in an external circuit.
We show that when one pulse is incident on the sample, the detected current signal reveals information about the compression of the optical pulse and it's CEP.
When two cross-polarized optical pulses with precise time-delay are incident on the dielectric, so that first (strong) pulse injects the carriers, while second (weak) pulse drives them towards electrodes, the detected current records a waveform as their relative delay is modified. The recorded time-delay signal can be used to reconstruct the waveform of the drive arm with the detection bandwidth covering more than 1 PHz (mid-infrared to ultraviolet).
An experimental comparison with conventional methods such as the electro-optical sampling and attosecond streaking was performed, which both verify its fidelity and provide new insight into carrier dynamics on the few femtosecond timescale. By using the new technique to measure nonlinear polarization and light-matter energy transfer in solids we demonstrate that the method can be used for attosecond physics experiments which were previously possible only with attosecond beamlines.
In addition we show the presence and control of non-linear effects in the dielectric samples by changing sample orientation and energies of both (injection and drive) pulses.
The new method allows the performance of attosecond measurements with the following advantages with respect to conventional methods: operation in ambient conditions (no vacuum attosecond beamline is required), compact and simple experimental setup, large detection bandwidth, large dynamic range of the detection, high signal to noise ratio, and an all-solid-state detection apparatus.