Second-harmonic generation and the conservation of spatiotemporal orbital angular momentum of light

Light with spatiotemporal orbital angular momentum (ST-OAM) is a recently discovered type of structured and localized electromagnetic field. This field carries characteristic space–time spiral phase structure and transverse intrinsic OAM. Here, we present the generation and characterization of the s...

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Bibliographic Details
Published in:Nature photonics 2021-08, Vol.15 (8), p.608-613
Main Authors: Gui, Guan, Brooks, Nathan J., Kapteyn, Henry C., Murnane, Margaret M., Liao, Chen-Ting
Format: Article
Language:English
Subjects:
639/624/1020/1095
639/766/400/385
Angular momentum
Applied and Technical Physics
Astigmatism
Conservation
Conversion
Electromagnetic fields
Light
Optical frequency
Photonics
Photons
Physics
Physics and Astronomy
Quantum Physics
Scaling
Second harmonic generation
Solid phases
Topology
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Summary:Light with spatiotemporal orbital angular momentum (ST-OAM) is a recently discovered type of structured and localized electromagnetic field. This field carries characteristic space–time spiral phase structure and transverse intrinsic OAM. Here, we present the generation and characterization of the second harmonic of ST-OAM pulses. We uncover the conservation of transverse OAM in a second-harmonic generation process, where the space–time topological charge of the fundamental field is doubled along with the optical frequency. Our experiment thus suggests a general ST-OAM nonlinear scaling rule, analogous to that in conventional OAM of light. Furthermore, we observe that the topology of a second-harmonic ST-OAM pulse can be modified by complex spatiotemporal astigmatism, giving rise to multiple phase singularities separated in space and time. Our study opens a new route for nonlinear conversion and scaling of light carrying ST-OAM, with the potential for driving other secondary ST-OAM sources of electromagnetic fields and beyond. The second-harmonic spatiotemporal orbital angular momentum of an optical pulse and its space–time topological charge conservation during frequency doubling are experimentally observed, opening opportunities for nonlinear conversion and scaling of photons carrying spatiotemporal orbital angular momentum.
ISSN:1749-4885
1749-4893
DOI:10.1038/s41566-021-00841-8