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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Controlling Light Polarization from Helical Travelling-Wave Nanoantennas
摘要： Light polarization is a key factor of modern photonics. Tailoring surface plasmons (SPs) in anisotropically-shaped metallic nanostructures introduces the prospect of polarization control at small scale [1]. However, the resulting components remain much larger than the wavelength of light. Here, we present a travelling-wave helical plasmonic antenna (TW-HPA) that overcomes this limit [2]. Due to its non-resonant nature, it differs from existing helical plasmonic structures [3-5], thus extending the concept of travelling-wave helical antenna [6] to optics. Our TW-HPA consists of a narrow gold-coated wire wound up in a screw-like shape forming a tiny helix (Fig. 1a). The gold-coated wire sustains a cutoff-free axially symmetric travelling SPs [7], locally excited with the dipolar mode of a rectangular aperture nanoantenna right at the helix's pedestal. In the course of propagation, the plasmon wire mode acquires orbital angular momentum (OAM). Due to the sharp curvatures, the OAM of the SP mode match the spin angular momentum (SAM) of free-space propagating photons [8]. On the basis of this OAM-to-SAM transfer, individual TW-HPA can produce circularly polarized directional light on the subwavelength scale through a swirling-plasmon effect. Such TW-HPAs can then be closely packed to build micron scale arrangements of tiny circularly polarized light sources of desired handedness and tunable intensities, which could open new perspectives in a large panel of photonic applications requiring local addressing, such as detectors, displays, optomagnetic recording as well as quantum information. By optically coupling four TW-HPAs of opposite handedness (Fig.1b), we obtained a phase plate occupying a volume smaller than a cubic wavelength whose polarization properties have never previously been demonstrated. Switching between left and right circular polarizations (LCP and RCP) occurs when the incident linear polarization is rotated by an angle of 52°, instead of 90° as for standard quarter wave plates. Based on the spin-orbit interaction of light, our method is versatile, robust and leads to ultracompact plasmonic polarizers and unconventional phase plates. Taken as individual or coupled structures, TW-PHAs may pave the way towards highly integrated polarization-encoded optics, particularly for the generation and control of spin-encoded photon qubits in quantum information and optical spintronics.
关键词： Light polarization,orbital angular momentum,surface plasmons,circularly polarized light,optical spintronics,quantum information,spin angular momentum,helical travelling-wave nanoantennas
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - 360° on Chip Optical Beam Steering Based on Superposition of Planar Spiral Orbital Angular Momentum Waves
摘要： Optical beam steering has been pursued in the past decade, largely motivated by its potential applications including optical communication and laser radar systems. Optical phased array (OPA) is a promising beam steering method, which has the potential advantages of low cost, chip scale, high resolution, fast scanning [1]. However, a main problem with current OPAs is the limited scanning angle. Steering angle of OPAs based on out-of-plane emitting planar waveguide gratings is typically < 50 degrees. End-fire OPA has a larger steering angle but still will be restricted to <180 degrees due to its geometry [2]. Circular OPA can provide 360-degree beam steering [3-4], but the existing proposals require large number of control elements which makes it very hard to realize. We report a silicon based OPA which is built on our previous works on orbital angular momentum (OAM) [5-6]. The OPA consists of N concentric micro-ring OAM emitters that, when injected with a transverse magnetic (TM) polarized mode, are capable of emitting ‘sideways’ – a planar spiral orbital angular momentum (PS-OAM) beam whose phase fronts spiral outwards in the micro-ring plane with li number of arms, as given by the dipole model [7-9], by superposition of such PS-OAM waves or azimuthal Fourier harmonics, ∑Ni=1aiexp(jliφ)exp(jφi),. The superposition of such PS-OAM waves is capable of providing a practical realization of beamforming in radiofrequency and optical domain [7-9], by controlling their amplitude ai, phase φi, and topological charge li. A narrow beam can be rotated 360 degrees easily by adjusting the phase shifters, and with its 3 dB beamwidth decreases with higher number of PS-OAM modes.
关键词： Optical phased array,Orbital angular momentum,Optical beam steering,Silicon photonics
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Optical Vortex Generation from an Anti-Resonant-Ring Picosecond Optical Parametric Oscillator
摘要： Optical vortices are beams with screw like (helical) phase variation along the propagation direction. This phase variation is given by exp(imθ) in the azimuthal plane, where m is the charge of optical vortices. Due to the doughnut shape intensity distribution and orbital angular momentum (OAM) content, optical vortices have found applications in various fields of science and technology. Commercially available mode converters transforming Gaussian beam into vortices suffer from the common drawback of low power handling capabilities and/or narrow wavelength coverage. To avoid such limitations, here we present a new technique of generating high power optical vortices over a wide wavelength range by using a Gaussian beam pumped anti-resonant-ring (ARR) optical parametric oscillator (OPO) [1]. By controlling the superposition of the Gaussian beams of an intracavity ARR, we have generated first-order HG modes [2] and further transformed into optical vortices using cylindrical lens [3], providing tunability across1457 nm to 1647 nm with an output power as high as 539 mW
关键词： optical parametric oscillator,optical vortices,orbital angular momentum,wavelength coverage,anti-resonant-ring
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Generation of Multiple Up-Converted OAM States from a Tunable Optical Vortex Parametric Laser Source
摘要： Optical vortices with a ring-shaped spatial form and an orbital angular momentum (OAM) of ?φ, arising from their helical wavefronts characterized by an azimuthal phase, exp(i?φ) (where ? is an integer termed the topological charge), have been widely exploiting a variety of research fields. These include optical trapping and manipulation, fluorescent microscopes with a high spatial resolution beyond the diffraction limit and materials processing. The aforementioned applications strongly desire wavelength-tunability and OAM-versatility to optical vortex sources. In this presentation, we report on the first generation of a signal output having multiple up-converted OAM states with ?(cid:3046) =3~5 (higher OAM than that of pump) from a nanosecond 2nd-order vortex (?(cid:3043) = 2) pumped singly resonant optical parametric oscillator (OPO) with a simple compact cavity configuration. The resulting idler exhibited negative OAM states with ?(cid:3036) =-1~-3.
关键词： Orbital angular momentum,OAM states,Wavelength-tunability,Optical vortices,Optical parametric oscillator
更新于2025-09-11 14:15:04
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Analysis of Bending-Induced Degradation of Orbital Angular Momentum Modes in Optical Fibers
摘要： In this work, bending-induced deterioration of orbital angular momentum (OAM) modes in ring core ?ber (RCF), photonic crystal ?ber (PCF), and vortex ?ber (VF) was theoretically investigated: Bending losses, coupling losses, and intermodal crosstalk at the interface between straight and bent optical ?bers were investigated from the modal analysis of those three types of OAM mode ?bers. In addition, the degradation of a topological charge number of an OAM mode due to the bending-induced birefringence and horizontal mode asymmetry was also investigated. Our investigation revealed that, in all aspects, the PCF is most robust to bending among the three types of optical ?bers, and the most serious bending-induced problem in the VF and the RCF is the degradation of the topological charge number. The allowed minimum bending radii of VF and RCF appeared to be ~15 and ~45 mm, respectively, for the speci?c structures considered in this work. We expect that the methodology and results of our quantitative analysis on bending-induced degradation of OAM modes will be of great use in the design of OAM mode ?bers for practical use.
关键词： ring core ?ber,photonic crystal ?ber,topological charge number,orbital angular momentum (OAM),vortex ?ber,?ber bending e?ect
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE Photonics Conference (IPC) - San Antonio, TX, USA (2019.9.29-2019.10.3)] 2019 IEEE Photonics Conference (IPC) - Shaping Optical Fibers to Mode Division Multiplex without MIMO
摘要： MIMO complexity can be reduced or avoided completely by proper design of the few mode optical fiber used for mode division multiplexing. Our focus is high index contrast fibers that avoid the formation of scalar modes, to favor vector modes with more limited modal interactions.
关键词： SDM,orbital angular momentum,OAM,spatial division multiplexing,MDM,mode division multiplexing
更新于2025-09-11 14:15:04
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High-order cylindrical vector beams with tunable topological charge up to 14 directly generated from a microchip laser with high beam quality and high efficiency
摘要： Large topological charge optical vortex beams carrying orbital angular momentum have potential applications on optical trapping, optical communication with high capacity, quantum information processing. However, the beam quality is degraded in vortex beams generated with spiral phase plates or resonator mirrors with defect spots and optical conversion efficiency in solid-state lasers is sacrificed by controlling the loss of resonator. It is a big challenge for generating high beam quality, high-order cylindrical vector beams with large topological charge in compact solid-state lasers. Here, high-order cylindrical vector beams [Laguerre-Gaussian (LG) modes with zero degree and order of l, LG0,l] with tunable topological charges up to 14 have been generated in an annular beam pumped Yb:YAG microchip laser by manipulating the pump power-dependent population inversion distribution. Efficient performance with optical efficiency of 17.5% has been achieved. The output power is 1.36 W for a vector-vortex laser with 14 topological charges. The pump power dependent wavelength tunable and dual-wavelength laser oscillation in vector-vortex beams has been observed by controlling the reabsorption loss at 1030 nm. Wavelength tunable, dual-wavelength (1030 and 1050 nm) laser oscillation has been achieved for vector-vortex beams with topological charges of 8, 9, and 10. The laser beam quality factor M2 close to the theoretical value (l + 1) has been achieved for LG0,l vector-vortex beams with tunable topological charges up to 14. This work provides a new effective method for generating large topological charge high-order cylindrical vector beams in solid-state microchip lasers with high efficiency and high beam quality.
关键词： orbital angular momentum,cylindrical vector beams,topological charge,Yb:YAG microchip laser,optical vortex beams
更新于2025-09-11 14:15:04
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Pancharatnam–Berry Optical Elements for Spin and Orbital Angular Momentum Division Demultiplexing
摘要： A Pancharatnam–Berry optical element is designed, fabricated, and optically characterized for the demultiplexing of beams with different polarization and orbital angular momentum states at the telecom wavelength of 1310 nm. The geometric phase control is achieved by fabricating properly-oriented subwavelength gratings on a silicon substrate, inducing a spatially-variant form birefringence. The digital grating pattern is transferred to the silicon substrate with a two-step nanofabrication protocol, using inductively coupled plasma reactive ion etching to transfer the resist pattern generated with high-resolution electron beam lithography. The optical characterization of the sample confirms the expected capability to sort circularly polarized optical beams with different handedness and orbital angular momentum. Encompassing optical element design and silicon photonics, the designed silicon metasurface paves the way to innovative devices for total angular momentum mode division multiplexing with unprecedented levels of integration.
关键词： subwavelength gratings,electron beam lithography,metasurfaces,silicon,orbital angular momentum,reactive ion etching,mode division multiplexing,polarization division multiplexing,Pancharatnam–Berry optical elements
更新于2025-09-10 09:29:36
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Self-bound droplets of light with orbital angular momentum
摘要： Systems with competing attractive and repulsive interactions have a tendency to condense into droplets. This is the case for water in a sink, liquid helium, and dipolar atomic gases. Here we consider a photon fluid which is formed in the transverse plane of a monochromatic laser beam propagating in an attractive (focusing) nonlocal nonlinear medium. In this setting we demonstrate the formation of the optical analog of matter-wave droplets and study their properties. The system we consider admits droplets that carry orbital angular momentum. We find bound states possessing liquidlike properties, such as bulk pressure and compressibility. Interestingly, these droplets of light, as opposed to optical vortices, form due to the competition between long-range s-wave (monopole) and d-wave (quadrupole) interactions as well as diffraction.
关键词： nonlocal nonlinear medium,orbital angular momentum,s-wave and d-wave interactions,liquidlike properties,photon fluid
更新于2025-09-10 09:29:36
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Azimuthal modulation of electromagnetically induced transparency using structured light
摘要： Recently a scheme has been proposed for detection of the structured light by measuring the transmission of a vortex beam through a cloud of cold rubidium atoms with energy levels of the Λ-type configuration [N. Radwell et al., Phys. Rev. Lett. 114, 123603 (2015)]. This enables observation of regions of spatially dependent electromagnetically induced transparency (EIT). Here we suggest another scenario for detection of the structured light by measuring the absorption profile of a weak nonvortex probe beam in a highly resonant five-level combined tripod and Λ (CTL) atom-light coupling setup. We demonstrate that due to the closed-loop structure of CTL scheme, the absorption of the probe beam depends on the azimuthal angle and orbital angular momentum (OAM) of the control vortex beams. This feature is missing in simple Λ or tripod schemes, as there is no loop in such atom-light couplings. One can identify different regions of spatially structured transparency through measuring the absorption of probe field under different configurations of structured control light.
关键词： orbital angular momentum,spatially dependent absorption,electromagnetically induced transparency,quantum interference,structured light
更新于2025-09-10 09:29:36