Calendar

Add to Calendar 10/17/2018 4:00 pm 10/17/2018 America/Chicago Physics Colloquium: "Nonlinear Optics and the Quantum Geometry of Crystals" DESCRIPTION:

Ohm’s Law, which says that electrical current depends linearly on applied electric field, is not a law of nature after all, merely a lowest-order approximation. Recently there has been an upsurge of interest in the response of crystals beyond the linear approximation, in particular 2nd order nonlinearity, which generates currents at the sum and difference frequencies of the applied fields.  Materials with a large 2nd order response are candidates for applications involving frequency generation and the conversion of light to dc current (photogalvanic effects). However, despite a long history of research in harmonic generation and photogalvanic effects, understanding their origin and ultimate limits has been gained only recently. The clue is that the condition that allows a nonzero 2nd order response – breaking of inversion symmetry – is the same as the condition for the existence of a curved bandstructure geometry.  In this talk I will describe the deep connections between photogalvanic effects, second-harmonic generation, and quantum geometry. I will also describe how our attempt to test these ideas experimentally led to the accidental discovery that the Weyl semimetal TaAs has the largest 2nd order susceptibility of any previously known crystal.

\n\nSPEAKER: Joe Orenstein, University of California Berkeley
141 Loomis Lab false

Physics Colloquium: "Nonlinear Optics and the Quantum Geometry of Crystals"

Speaker Joe Orenstein, University of California Berkeley
Date: 10/17/2018
Time: 4 p.m.
Location: 141 Loomis Lab
Event Contact: Suzanne Hallihan
217-244-7151
shalliha@illinois.edu
Cost: none
Sponsor: Department of Physics
Event Type: Other
 

Ohm’s Law, which says that electrical current depends linearly on applied electric field, is not a law of nature after all, merely a lowest-order approximation. Recently there has been an upsurge of interest in the response of crystals beyond the linear approximation, in particular 2nd order nonlinearity, which generates currents at the sum and difference frequencies of the applied fields.  Materials with a large 2nd order response are candidates for applications involving frequency generation and the conversion of light to dc current (photogalvanic effects). However, despite a long history of research in harmonic generation and photogalvanic effects, understanding their origin and ultimate limits has been gained only recently. The clue is that the condition that allows a nonzero 2nd order response – breaking of inversion symmetry – is the same as the condition for the existence of a curved bandstructure geometry.  In this talk I will describe the deep connections between photogalvanic effects, second-harmonic generation, and quantum geometry. I will also describe how our attempt to test these ideas experimentally led to the accidental discovery that the Weyl semimetal TaAs has the largest 2nd order susceptibility of any previously known crystal.

To request disability-related accommodations for this event, please contact the person listed above, or the unit hosting the event.

Event Mailing List

Receive Illinois Physics events weekly in your inbox.

Sign-up!


Remove me!