Electronics at Optical Frequencies

With the advent of ultrafast optics and controllable waveforms consisting of only a few oscillations of the electric field, the idea of controlling electrons at the frequency of light was born. This established the potential of using a controlled optical waveform to switch electronic circuit elements at the frequency of an optical wave, typically on the order of 0.1 to 1 petahertz(1015 Hz). This exceeds the frequency of the fastest electronic devices by two to three orders of magnitude and the clock rates of modern computers by up to six orders of magnitude. Tothis end, many pioneering experiments have shown that optical waveforms can be used to drive attosecond electron currents at metal-vacuum interfaces, in dielectric large bandgap materials or in air. This thesis shows how integrated metallic nanoantennas are utilized to enhance the electric field of optical few-cycle pulses in nanometer-sized hotspots, generating sub-cycle field emission with only picojoule-level pulse energies. Exploiting the attosecond-fast currents on the nanoscale, petahertz bandwidth field sampling with 5 femtojoule sensitivity is experimentally demonstrated [20]. The influence of antenna symmetry and device design on the sampling frequency response is investigated theoretically to guide application specific design strategies [21]. To further test the integrated nanoantenna platform, we have developed a passively CEP-stable sub-2-cycle laser source that produces 16 fs duration pulsesat a central wavelength of 2.7 µm with > 84 nJ energy at a repetition rate of 50 kHz. The system is based on adiabatic difference generation [22], and significantly simplifies previous implementations by relying solely on material-based compression. Furthermore, the CEP stability of adiabatic difference generation is measured for the first time and shows excellent passive stability of 190 mrad rms. We show that by using the newly developed mid-infrared sub-2-cycle source, the CEP dependent yield of a single nanoantenna is significantly improved by a factor of 30 from a previous 0.1 electrons per laser shot to > 3 electrons [10, 23]. Thanks to this significant improvement, and by illuminating up to 1000 antennas, we produce fully carrier-envelope phase (CEP) dependent currents of up to 3000 electrons per shot, improving previous results by three orders of magnitude [23]. The results of this work will open many interesting avenues for the exploration of optical frequency electronics based on integrated nanoantennas, such as ultra-broadband time spectroscopy in the infrared continuously covering the terahertz to visible spectrum, or petahertz bandwidth logic circuits