A milestone in petahertz electronics

March 13, 2018, ETH Zurich
(A) An intense few-cycle infrared (IR) laser pulse is combined with a single attosecond probe pulse with a spectrum in the extreme-ultraviolet (XUV) energy regime. (B) & (C) Illustration of IR-induced inter- and intra-band transitions. Credit: Adapted from Schlaepfer et al., Nature Physics doi:10.1038/s41567-018-0069-0 (2018).

In a semiconductor, electrons can be excited by absorbing laser light. Advances in the past decade have enabled measuring this fundamental physical mechanism on timescales below a femtosecond (10-15 s). Now, physicists at ETH Zurich have resolved the response of electrons in gallium arsenide at the attosecond (10-18 s) timescale, and gained unexpected insights for future ultrafast opto-electronic devices with operation frequencies in the petahertz regime.

Gallium arsenide is a technologically important narrow-band-gap semiconductor in which the excitation of from the valence into the conduction band produces charge carriers that can transport electrical current through electronics components. In addition to this so-called inter-band transition, carriers can also be accelerated within the individual bands as the electrons interact with the . This is due to the strong electric field associated with the laser light, leading to intra-band motion. However, it is not known which of the two mechanisms dominates the response to a short intense laser pulse, and how their interplay effects the carrier injection into the conduction band.

Fabian Schlaepfer and his colleagues in the group of Ursula Keller in the Department of Physics have now studied these processes for the first time at the attosecond timescale, combining transient absorption spectroscopy with state-of-the-art first principles calculations. As they report in a paper that appears today online in Nature Physics, they found that intra-band motion has indeed an important role, as it significantly enhances the number of electrons that get excited into the conduction band.

This finding was unexpected because intra-band motion alone is unable to produce in the . These results therefore represent an important step forward in understanding the light-induced electron dynamics in a semiconductor on the attosecond timescale, which will be of practical relevance for future electronics and optoelectronics devices, whose dimensions become ever smaller, and the electric fields involved ever stronger and the dynamics ever faster.

Explore further: Attoseconds break into atomic interior

More information: F. Schlaepfer et al, Attosecond optical-field-enhanced carrier injection into the GaAs conduction band, Nature Physics (2018). DOI: 10.1038/s41567-018-0069-0

Related Stories

Attoseconds break into atomic interior

February 27, 2018

A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons ...

Scientists found excitons in nickel oxide for the first time

January 15, 2018

Russian scientists from Ural Federal University (UrFU), together with their colleagues from Institute of Metal Physics of the Ural Department of Russian Academy of Sciences, have studied fundamental characteristics of nickel ...

Physicists publish new findings on electron emission

September 21, 2017

Even more than 100 years after Einstein's explanation of photoemission the process of electron emission from a solid material upon illumination with light still poses challenging surprises. In the report now published in ...

Explained: Bandgap

July 23, 2010

Why do some materials work well for making solar cells or light-emitting diodes (LEDs), while other materials don't? One key factor is having the right bandgap.

Electrons at the speed limit

August 26, 2016

Electronic components have become faster and faster over the years, thus making powerful computers and other technologies possible. Researchers at ETH Zurich have now investigated how fast electrons can ultimately be controlled ...

Recommended for you

Designing a new material for improved ultrasound

March 22, 2018

Development of a theoretical basis for ultrahigh piezoelectricity in ferroelectric materials led to a new material with twice the piezo response of any existing commercial ferroelectric ceramics, according to an international ...

Weird superconductor leads double life

March 21, 2018

Until about 50 years ago, all known superconductors were metals. This made sense, because metals have the largest number of loosely bound "carrier" electrons that are free to pair up and flow as electrical current with no ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.