Faster Way to Measure the Electric Field of Light

Detection of currents induced in ambient air plasma by a pair of cross-polarized laser pulses is used to sample the electric field of light waves. (Source: A. Korobenko)

Researchers at University of Ottawa have created a new method to measure the temporal evolution of electric fields with optical frequencies. The new approach, which works in ambient air, faci­litates the direct measure­ment of the field waveform and could lead to breakthroughs in high-speed electronics.

“The aim of our project is to resolve the electric field oscil­lations in a light pulse. This allows one to control the motion of electrons in quantum systems on shortest time scales and may lead to important applications such as petahertz elec­tronics – that are a million times faster than typical modern processors“, postdoc Aleksey Korobenko says .

Such a measurement was first achieved using atto­second streaking – a generali­zation of the long-known conventional streak camera. When irradiated with a short electro­magnetic pulse, the gas molecules give up their electrons that continue their motion, experiencing the pull from the field of a second, streaking, pulse. Measuring the velocity that the electrons acquire due to this pull allows one to re­construct the streaking pulse on atto­second time scales.

“In our work we demons­trated that instead of measuring the velocities of individual electrons in low-density gas samples, which requires high vacuum condi­tions and/or a complicated setup, one can simply measure the current induced in air plasma under ambient conditions. We probe this current using a pair of metal electrodes. which faci­litates a much simpler and faster measure­ment of a light wave oscil­lation”, Krobenko says. “We can access the time scales of the optical field oscil­lations in an inex­pensive, fast and robust way. Owing to its simplicity, our method can become a useful tool for the ultrashort lasers research community, aiding the development of a next generation petahertz elec­tronics.”

The experim­ents were carried out using a unique, state-of-the-art, high-power laser generating ultra­short pulses from the visible to the infrared spectrum. Performing a measurement of these pulses under different experimental conditions, we bench­marked our method against the established measurement techniques. This study is an inter­national colla­boration with researchers from the Ludwig-Maximilian Univer­sity of Munich, the Max-Planck Institute for Quantum Optics in Germany and the Joint Atto­second Science Lab (NRC and uOttawa). (Source: U. Ottawa)

Reference: A. Korobenko et al.: Femtosecond streaking in ambient air, Optica 7, 1372 (2020); DOI: 10.1364/OPTICA.398846

Link: Joint Attosecond Science Laboratory, National Research Council of Canada and University of Ottawa, Ottawa, Canada

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