Nav: Home

Light from inside the tunnel

June 30, 2020

Steering and monitoring the light-driven motion of electrons inside matter on the time-scale of a single optical cycle is a key challenge in ultrafast light wave electronics and laser-based material processing. Physicists from the Max Born Institute in Berlin and the University of Rostock have now revealed a so-far overlooked nonlinear optical mechanism that emerges from the light-induced tunneling of electrons inside dielectrics. For intensities near the material damage threshold, the nonlinear current arising during tunneling becomes the dominant source of bright bursts of light, which are low-order harmonics of the incident radiation. These findings, which have just been published in Nature Physics, significantly expand both the fundamental understanding of optical non-linearity in dielectric materials and its potential for applications in information processing and light-based material processing.

Our current understanding of non-linear optics at moderate light intensities is based on the so-called Kerr non-linearity, which describes the non-linear displacement of tightly bound electrons under the influence of an incident optical light field. This picture changes dramatically when the intensity of this light field is sufficiently high to eject bound electrons from their ground state. At long wavelengths of the incident light field, this scenario is associated with the phenomenon of tunneling, a quantum process where an electron performs a classically forbidden transit through a barrier formed by the combined action of the light force and the atomic potential.

Already since the 1990's and pioneered by studies from the Canadian scientist François Brunel, the motion of electrons that have emerged at the "end of the tunnel", which happens with maximal probability at the crest of the light wave, has been considered as an important source for optical non-linearity. This picture has now changed fundamentally. "In the new experiment on glass, we could show that the current associated with the quantum mechanical tunneling process itself creates an optical non-linearity that surpasses the traditional Brunel mechanism", explains Dr. Alexandre Mermillod-Blondin from the Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, who supervised the experiment. In the experiment, two ultrashort light pulses with different wavelengths and slightly different propagation directions were focused onto a thin slab of glass, and a time- and frequency-resolved analysis of the emerging light emission was performed.

Identification of the mechanism responsible for this emission was made possible by a theoretical analysis of the measurements that was performed by the group of Prof. Thomas Fennel, who works at the University of Rostock and at the Max Born Institute in the framework of a DFG Heisenberg Professorship. "The analysis of the measured signals in terms of a quantity that we termed the effective non-linearity was key to distinguish the new ionization current mechanism from other possible mechanisms and to demonstrate its dominance", explains Fennel.

Future studies using this knowledge and the novel metrology method that was developed in the course of this work may enable researchers to temporally resolve and steer strong-field ionization and avalanching in dielectric materials with unprecedented resolution, ultimately possibly on the time-scale of a single cycle of light.
-end-


Forschungsverbund Berlin

Related Electrons Articles:

Plasma electrons can be used to produce metallic films
Computers, mobile phones and all other electronic devices contain thousands of transistors, linked together by thin films of metal.
Flatter graphene, faster electrons
Scientists from the Swiss Nanoscience Institute and the Department of Physics at the University of Basel developed a technique to flatten corrugations in graphene layers.
Researchers develop one-way street for electrons
The work has shown that these electron ratchets create geometric diodes that operate at room temperature and may unlock unprecedented abilities in the illusive terahertz regime.
Photons and electrons one on one
The dynamics of electrons changes ever so slightly on each interaction with a photon.
Using light to put a twist on electrons
Method with polarized light can create and measure nonsymmetrical states in a layered material.
What if we could teach photons to behave like electrons?
The researchers tricked photons - which are intrinsically non-magnetic - into behaving like charged electrons.
Electrons in rapid motion
Researchers observe quantum interferences in real-time using a new extreme ultra-violet light spectroscopy technique.
Taming electrons with bacteria parts
In a new study, scientists at the MSU-DOE Plant Research Laboratory report a new synthetic system that could guide electron transfer over long distances.
Hot electrons harvested without tricks
Semiconductors convert energy from photons into an electron current. However, some photons carry too much energy for the material to absorb.
Cooling nanotube resonators with electrons
In a study in Nature Physics, ICFO researchers report on a technique that uses electron transport to cool a nanomechanical resonator near the quantum regime.
More Electrons News and Electrons Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Our Relationship With Water
We need water to live. But with rising seas and so many lacking clean water – water is in crisis and so are we. This hour, TED speakers explore ideas around restoring our relationship with water. Guests on the show include legal scholar Kelsey Leonard, artist LaToya Ruby Frazier, and community organizer Colette Pichon Battle.
Now Playing: Science for the People

#568 Poker Face Psychology
Anyone who's seen pop culture depictions of poker might think statistics and math is the only way to get ahead. But no, there's psychology too. Author Maria Konnikova took her Ph.D. in psychology to the poker table, and turned out to be good. So good, she went pro in poker, and learned all about her own biases on the way. We're talking about her new book "The Biggest Bluff: How I Learned to Pay Attention, Master Myself, and Win".
Now Playing: Radiolab

Uncounted
First things first: our very own Latif Nasser has an exciting new show on Netflix. He talks to Jad about the hidden forces of the world that connect us all. Then, with an eye on the upcoming election, we take a look back: at two pieces from More Perfect Season 3 about Constitutional amendments that determine who gets to vote. Former Radiolab producer Julia Longoria takes us to Washington, D.C. The capital is at the heart of our democracy, but it's not a state, and it wasn't until the 23rd Amendment that its people got the right to vote for president. But that still left DC without full representation in Congress; D.C. sends a "non-voting delegate" to the House. Julia profiles that delegate, Congresswoman Eleanor Holmes Norton, and her unique approach to fighting for power in a virtually powerless role. Second, Radiolab producer Sarah Qari looks at a current fight to lower the US voting age to 16 that harkens back to the fight for the 26th Amendment in the 1960s. Eighteen-year-olds at the time argued that if they were old enough to be drafted to fight in the War, they were old enough to have a voice in our democracy. But what about today, when even younger Americans are finding themselves at the center of national political debates? Does it mean we should lower the voting age even further? This episode was reported and produced by Julia Longoria and Sarah Qari. Check out Latif Nasser's new Netflix show Connected here. Support Radiolab today at Radiolab.org/donate.