We extend all-optical quasi-phase matching of high-order harmonic generation into spectral regions where conventional phase matching is not possible. The high laser intensities required to generate harmonics at energy >130 eV, coupled with the resulting high level of ionization, preclude conventional phase matching in all nonlinear media. Selective enhancement factors between 40 and 150 in the flux of harmonics at photon energies around 140 eV are demonstrated using a train of two counterpropagating pulses.
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http://dx.doi.org/10.1364/ol.33.000174 | DOI Listing |
Nanophotonics
July 2024
State Key Laboratory of Precision Spectroscopy, School of Physics and Electronic Science, East China Normal University, Shanghai 200241, China.
Lithium niobate on insulator (LNOI) combines a variety of optoelectronic properties and can meet practical performance requirements that are uncommon in optoelectronic materials. This review introduces the fundamentals and the photonic device concepts that arise from the LNOI materials platform. Firstly, the nonlinear optical response of LNOI is presented, including birefringent phase matching (BPM), modal phase matching (MPM), and quasi-phase matching (QPM).
View Article and Find Full Text PDFNanophotonics
August 2024
State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-Sen University, Guangzhou 510275, China.
The concept of orbital angular momentum (OAM) of light has not only advanced fundamental physics research but also yielded a plethora of practical applications, benefitting from the abundant methods for OAM generation based on linear, nonlinear and combined schemes. The combined scheme could generate octave-separating OAM beams, potentially increasing the channels for optical communication and data storage. However, this scheme faces a challenge in achieving high conversion efficiency.
View Article and Find Full Text PDFWe present an approach to generate stable vortex solitons (VSs) in rotating quasi-phase-matched photonic crystals with quadratic nonlinearity. The photonic crystal is introduced with a checkerboard structure, which can be realized using available technology. The VSs are constructed as four-peak vortex modes of two types: rhombuses and squares.
View Article and Find Full Text PDFPolarization-entangled photons are indispensable to numerous quantum technologies and fundamental studies. In this paper, we propose and demonstrate what we believe to be a novel source that generates collinear polarization-entangled photons by simultaneously achieving two distinct types of phase-matching conditions (noncritically birefringent and quasi phase matching) in a periodically poled nonlinear crystal with a large poling period of 2 mm. The photon pairs are generated in a polarization-entangled state with a fidelity and concurrence of 0.
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