High-order Harmonic Generation in a Bulk Crystal

Wednesday, March 9, 2011 - 3:00pm

Speaker: Shambhu Ghimire, PULSE Institute Research Associate

Shambhu Ghimire received his Ph.D. in 2007 from J. R. McDonald's Lab at Kansas State University, with a thesis titled "Study on Generation of Attosecond pulses with Polarization Gating." He worked as a postdoc in David Reis's group at the University of Michigan before joining the PULSE institute as research associate in 2009.

Program Description

High-order harmonic generation (HHG) is a nonlinear optical process that enables the creation of light pulses at frequencies much higher than that from the input laser. This has been a standard route in producing attosecond pulses in XUV. The host medium is typically a gas where the physics can be described in terms of field ionization and recollision in isolated particles. In a solid, the interaction must include multiple ionization and recombination sites changing the fundamental nature of the interaction. Recently, we have reported HHG in bulk crystals. We have observed harmonics up to the 25th order in single crystal ZnO when seeded with an intense mid-infrared laser, and the harmonics spectra show a clear non-perturbative character. We present a simple band model for the generation of non-perturbative HHG in strongly driven periodic solids in order to explain our data which differ fundamentally from the gas phase. Our results have important implications for the understanding of attosecond electron dynamics and other non-equilibrium band-structure-related phenomena in strongly driven bulk solids. Time permitting, the talk will also cover the feasibility of using the high intensity THz pulses from coherent transition radiation at LCLS to strongly drive periodic solids and study non-perturbative phenomena at longer wavelength.

Nature Physics Article: http://www.nature.com/nphys/journal/v7/n2/pdf/nphys1847.pdf

Nature Physics News and Views Article: http://www.nature.com/nphys/journal/v7/n2/full/nphys1913.html

High-order Harmonic Generation in a Bulk Crystal
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