scholarly journals Ways to achieve efficient non-local vortex beam generation

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Wenzhe Liu ◽  
Lei Shi ◽  
Jian Zi ◽  
Che Ting Chan
Keyword(s):  
Bound States ◽  
Periodic Structures ◽  
Generation Efficiency ◽  
Factors Affecting ◽  
Full Wave ◽  
Novel Approach ◽  
Non Local ◽  
Vortex Beams ◽  
Space Polarization ◽  
The Continuum

Abstract Based on the insights into the phenomenon of bound states in the continuum, a novel approach utilizing the momentum-space polarization morphologies of periodic structures to generate vortex beams (VBs) has been proposed. Such periodic structures modulate beams in a nonlocal way and require no precise alignment. However, the efficiency of such an approach has not been analyzed in detail, and the efficiency in previous realizations is far from optimized. Here, we analyze the factors affecting the efficiency of nonlocal VB generation. We show that the maximal efficiency cannot exceed 25% if the periodic structure carries only singlet resonances. To go beyond this limit, we propose two approaches to improve efficiency. We theoretically analyze the mechanisms and verify the approaches by full-wave simulations. Both of the approaches serve to improve the generation efficiency by several folds.

scholarly journals Generating optical vortex beams by momentum-space polarization vortices centred at bound states in the continuum

2020 ◽  
Vol 14 (10) ◽  
pp. 623-628 ◽  
Author(s):  
Bo Wang ◽  
Wenzhe Liu ◽  
Maoxiong Zhao ◽  
Jiajun Wang ◽  
Yiwen Zhang ◽  
...  
Keyword(s):  
Momentum Space ◽  
Bound States ◽  
Optical Vortex ◽  
Vortex Beams ◽  
Space Polarization ◽  
The Continuum

scholarly journals Bound states in the continuum in periodic structures with structural disorder

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ekaterina E. Maslova ◽  
Mikhail V. Rybin ◽  
Andrey A. Bogdanov ◽  
Zarina F. Sadrieva
Keyword(s):  
Bound States ◽  
Periodic Structures ◽  
Structural Disorder ◽  
Practical Implementation ◽  
Photonic Structure ◽  
Mode Localization ◽  
Effective Reduction ◽  
System Length ◽  
Symmetry Protected ◽  
The Continuum

Abstract We study the effect of structural disorder on the transition from the bound states in the continuum (BICs) to quasi-BICs by the example of the periodic photonic structure composed of two layers of parallel dielectric rods. We uncover the specificity in the robustness of the symmetry-protected and accidental BICs against various types of structural disorder. We analyze how the spatial mode localization induced by the structural disorder results in an effective reduction of the system length and limits the Q factor of quasi-BICs. Our results are essential for the practical implementation of BICs especially in natural and self-assembled photonic structures, where the structural disorder plays a crucial role.

scholarly journals Significantly enhanced second-harmonic generations with all-dielectric antenna array working in the quasi-bound states in the continuum and excited by linearly polarized plane waves

Nanophotonics ◽  
2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Zhanghua Han ◽  
Fei Ding ◽  
Yangjian Cai ◽  
Uriel Levy
Keyword(s):  
Second Harmonic Generation ◽  
Magnetic Dipole ◽  
Harmonic Generation ◽  
Bound States ◽  
Second Harmonic ◽  
Generation Efficiency ◽  
Second Harmonic Generation Efficiency ◽  
Linearly Polarized ◽  
Magnetic Dipole Resonances ◽  
The Continuum

AbstractThe recently emerging all-dielectric optical nanoantennas based on high-index semiconductors have proven to be an effective and low-loss alternative to metal-based plasmonic structures for light control and manipulations of light–matter interactions. Nonlinear optical effects have been widely investigated to employ the enhanced interactions between incident light and the dielectrics at the Mie-type resonances, and in particular magnetic dipole resonances, which are supported by the semiconductor. In this paper, we explore the novel phenomenon of bound states in the continuum supported by high-index semiconductor nanostructures. By carefully designing an array of nanodisk structures with an inner air slot as the defect, we show that a novel high quality-factor resonance achieved based on the concept of bound state in the continuum can be easily excited by the simplest linearly polarized plane wave at normal incidence. This resonance further enhances the interactions between light and semiconductors and boosts the nonlinear effects. Using AlGaAs as the nonlinear material, we demonstrate a significant increase in the second-harmonic generation efficiency, up to six orders of magnitude higher than that achieved by magnetic dipole resonances. In particular, a second-harmonic generation efficiency around 10% can be numerically achieved at a moderate incident pump intensity of 5 MW/cm2.

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