Creating high-harmonic beams with controlled orbital angular momentum.
A beam with an angular-dependant phase Φ = ℓϕ about the beam axis carries an orbital angular momentum of ℓℏ per photon. Such beams are exploited to provide superresolution in microscopy. Creating extreme ultraviolet or soft-x-ray beams with controllable orbital angular momentum is a critical step towards extending superresolution to much higher spatial resolution. We show that orbital angular momentum is conserved during high-harmonic generation. Experimentally, we use a fundamental beam with |ℓ| = 1 and interferometrically determine that the harmonics each have orbital angular momentum equal to their harmonic number. Theoretically, we show how any small value of orbital angular momentum can be coupled to any harmonic in a controlled manner. Our results open a route to microscopy on the molecular, or even submolecular, scale.
Joint Attosecond Science Laboratory, University of Ottawa and National Research Council, Ottawa K1A 0R6, Canada.
Genevieve
G
Gariepy
Department of Physics, University of Ottawa, Ottawa K1N 6N5, Canada and IPaQS, SUPA, Heriot-Watt, Edinburgh EH14 4AS, United Kingdom.
Jonathan
J
Leach
Joint Attosecond Science Laboratory, University of Ottawa and National Research Council, Ottawa K1A 0R6, Canada and Center for Relativistic Laser Science, Institute for Basic Science (IBS), Gwangju 500-712, Republic of Korea and Department of Physics and Photon Science, Gwangju Institute of Science and Technology (GIST), Gwangju 500-712, Republic of Korea.
Kyung Taec
KT
Kim
Joint Attosecond Science Laboratory, University of Ottawa and National Research Council, Ottawa K1A 0R6, Canada.
T J
TJ
Hammond
Joint Attosecond Science Laboratory, University of Ottawa and National Research Council, Ottawa K1A 0R6, Canada and Department of Physics, Ben-Gurion University, Beer-Sheva 84105, Israel.
E
E
Frumker
Department of Physics, University of Ottawa, Ottawa K1N 6N5, Canada and Institute of Optics, University of Rochester, Rochester, New York 14627, USA.
Robert W
RW
Boyd
Joint Attosecond Science Laboratory, University of Ottawa and National Research Council, Ottawa K1A 0R6, Canada.
P B
PB
Corkum