High-order-harmonic generation driven by pulses with angular spatial chirp

We present and analyze a technique to drive high-order harmonics by laser pulses with an angular spatial chirp. Results of our numerical simulations show that each harmonic is emitted with an angular chirp which scales inversely with the harmonic order and leads to additional control of the spatial and temporal resolution of the spectrum. In particular, the use of angular chirp leads to separation of the harmonics in two dimensions where (i) high spectral resolution can be achieved and (ii) the temporal periodicity of the harmonic pulse trains can be controlled. We show that this technique does not require carrier-envelope-phase stabilization when using few-cycle laser pulses.The authors thank Profs. Margaret Murnane and Henry Kapteyn for stimulating discussions and support. C.H.-G. acknowledges support from the Marie Curie International Outgoing Fellowship within the EU Seventh Framework Programme for Research and Technological Development (2007-2013), under REA Grant Agreement No. 328334, and from Junta de Castilla y León (Project SA116U13, UIC016) and MINECO (FIS2013-44174-P, FIS2015-71933-REDT). A.J.-B., A.B., and C.D. acknowledge support from AFOSR FA9550-10-0561. C.D. acknowledges support from NSF EUV ERC. D.H. gratefully acknowledges supports from the Department of Energy BES Award DE-FG02-99ER14982. This work utilized the Janus supercomputer, which is supported by the U.S. National Science Foundation (Grant No. CNS-0821794) and the University of Colorado Boulder