Wednesday, September 15, 2021

Femtosecond Time Resolving Sensor

University of Central Florida, Orlando, and University of Ottawa, Canada, publish an paper "Single-shot measurement of few-cycle optical waveforms on a chip" by Yangyang Liu, John E. Beetar, Jonathan Nesper, Shima Gholam-Mirzaei, Michael Chini. The time resolution is beyond belief. The light propagates by just 300nm in 1 fs time, less than a wavelength in visible band.

"The measurement of transient optical fields has proven critical to understanding the dynamical mechanisms underlying ultrafast physical and chemical phenomena, and is key to realizing higher speeds in electronics and telecommunications. Complete characterization of optical waveforms, however, requires an optical oscilloscope capable of resolving the electric field oscillations with sub-femtosecond resolution and with single-shot operation. Here, we show that strong-field nonlinear excitation of photocurrents in a silicon-based image sensor chip can provide the sub-cycle optical gate necessary to characterize carrier-envelope phase-stable optical waveforms in the mid-infrared. By mapping the temporal delay between an intense excitation and weak perturbing pulse onto a transverse spatial coordinate of the image sensor, we show that the technique allows single-shot measurement of few-cycle waveforms."

The measurements setup uses a Thorlabs DCC1545M camera based on 8b 1.3MP CMOS sensor with fairly modest spec. At least, some of the nice things do not require high performing sensors:


  1. Impressive time resolution... Also impressive that they used apparently a quite old camera (it is marked 'obsolete' on the thorlabs website. To me the sensor visible in a foto on looks like a MT9M001, this must be about 20 years old, one of the first Micron RS products. I think Eric could probably tell stories about this sensor, right?

  2. Then you could wonder how much this can further improve when one of these sub-electron noise imagers availalbe today is used. That was also the motivation of our work on two-photon absorption, presented at IISW this and next week. The non-linear two-photon or multiple-photon absorption process can provide temporal resolution outperforming the single photon absorption process.

    1. Just needs a lot of radiance to actually get a significant enough probability of matching 2 photons and an electron in the valence band at the right time and space... What's the application you have in mind where such radiance levels are present? Or are you thinking about regular multiphoton microscopy? If so, what's the novelty?


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