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Register a new userSpin constrained orbital angular momentum control in high-harmonic generation
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The interplay between spin and orbital angular momentum in the up-conversion process allows us to control the macroscopic wave front of high harmonics by manipulating the microscopic polarizations of the driving field. We demonstrate control of orbital angular momentum in high harmonic generation from both solid and gas phase targets using the selection rules of spin angular momentum. The gas phase harmonics extend the control of angular momentum to extreme-ultraviolet wavelength. We also propose a bi-color scheme to produce spectrally separated extreme-ultraviolet radiation carrying orbital angular momentum.
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Optical vortices are currently one of the most intensively studied topics in optics. These light beams, which carry orbital angular momentum (OAM), have been successfully utilized in the visible and infrared in a wide variety of applications. Moving to shorter wavelengths may open up completely new research directions in the areas of optical physics and material characterization. Here, we report on the generation of extreme-ultraviolet optical vortices with femtosecond duration carrying a controllable amount of OAM. From a basic physics viewpoint, our results help to resolve key questions such as the conservation of angular momentum in highly-nonlinear light-matter interactions, and the disentanglement and independent control of the intrinsic and extrinsic components of the photons angular momentum at short-wavelengths. The methods developed here will allow testing some of the recently proposed concepts such as OAM-induced dichroism, magnetic switching in organic molecules, and violation of dipolar selection rules in atoms.
We present an experimental technique using orbital angular momentum (OAM) in a fundamental laser field to drive High Harmonic Generation (HHG). The mixing of beams with different OAM allows to generate two laser foci tightly spaced to study the phase and amplitude of HHG produced in diatomic nitrogen. Nitrogen is used as a well studied system to show the quality of OAM based HHG interferometry.
We experimentally study the behavior of orbital angular momentum (OAM) of light in a noncollinear second harmonic generation (SHG) process. The experiment is performed by using a type I BBO crystal under phase matching conditions with femtosecond pumping fields at 830 nm. Two specular off-axis vortex beams carrying fractional orbital angular momentum at the fundamental frequency (FF) are used. We analyze the behavior of the OAM of the SH signal when the optical vortex of each input field at the FF is displaced from the beams axis. We obtain different spatial configurations of the SH field, always carrying the same zero angular momentum.
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. In this work, we present the generation and characterization of the second-harmonic of ST-OAM pulses. We uncovered 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.
Light beams carrying orbital angular momentum (OAM) have led to stunning applications in various fields from quantum information to microscopy. In this letter, we examine OAM from the recently discovered high-harmonic generation (HHG) in semiconductor crystals. HHG from solids could be a valuable approach for integrated high-flux short-wavelength coherent light sources. The solid state nature of the generation medium allows the possibility to tailor directly the radiation at the source of the emission and offers a substantial degree of freedom for spatial beam shaping. First, we verify the fundamental principle of the transfer and conservation of the OAM from the generation laser to the harmonics. Second, we create OAM beams by etching a spiral zone structure directly at the surface of a zinc oxide crystal. Such diffractive optics act on the generated harmonics and produces focused optical vortices with nanometer scale sizes that may have potential applications in nanoscale optical trapping and quantum manipulation.
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