High harmonic emission from a superposition of multiple unrelated frequency fields.
We report observations and analysis of high harmonic generation driven by a superposition of fields at 1290 nm and 780 nm. These fields are not commensurate in frequency and the superposition leads to an increase in the yield of the mid-plateau harmonics of more than two orders of magnitude compared to using the 1290 nm field alone. Significant extension of the cut-off photon energy is seen even by adding only a small amount of the 780 nm field. These observations are explained by calculations performed in the strong field approximation. Most importantly we find that enhancement is found to arise as a consequence of both increased ionization in the sum-field and modification of the electron trajectories leading to an earlier return time. The enhanced yield even when using modest intensity fields of 5 x 10(13) Wcm(-2) is extended to the 80 eV range and is a promising route to provide a greater photon number for applications in XUV imaging and time-resolved experiments at a high repetition rate.
Siegel
T
T
Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BW, UK.
Torres
R
R
Hoffmann
D J
DJ
Brugnera
L
L
Procino
I
I
Zaïr
A
A
Underwood
Jonathan G
JG
Springate
E
E
Turcu
I C E
IC
Chipperfield
L E
LE
Marangos
J P
JP
D000537:Aluminum Oxide / Q000737:chemistry; D004574:Electromagnetic Fields; D004583:Electrons; D004867:Equipment Design; D007477:Ions; D007834:Lasers; D017711:Nonlinear Dynamics; D016011:Normal Distribution; D055095:Optics and Photonics; D017785:Photons; D010825:Physics / Q000379:methods; D014025:Titanium / Q000737:chemistry
D007477:Ions; D014025:Titanium; D000537:Aluminum Oxide