Showing papers by "Qiwen Zhan published in 2012"
TL;DR: A low-threshold single-wavelength all-fiber laser generating cylindrical vector beams using a few-mode fiber Bragg grating with very good modal symmetry and polarization purity higher than 94%.
Abstract: We propose and demonstrate a low-threshold single-wavelength all-fiber laser generating cylindrical vector beams using a few-mode fiber Bragg grating. Both radially and azimuthally polarized beams have been generated with very good modal symmetry and polarization purity higher than 94%. The radially and azimuthally polarized modes can be switched by simply adjusting the polarization controllers built in the fiber laser cavity. This fiber laser operates at a single wavelength of 1053 nm with a 3 dB linewidth of less than 0.02 nm, signal-to-background ratio of more than 55 dB, and a threshold as low as 16 mW. A new method for the polarization purity measurement is also proposed.
153 citations
TL;DR: In this article, a three-dimensional interconnected optical bubble array (optical chain) was constructed and manipulated with optimized structure through a reversing field radiated from an electric-magnetic dipole array.
Abstract: We propose a systematic approach to create a three-dimensional interconnected optical bubble array (optical chain) in the focal volume of a high numerical-aperture objective. Radiation from electric and magnetic dipoles are introduced to interpret the focusing characteristics of radially and azimuthally polarized light. Utilizing the connections between the highly focused vector beams and reversed radiation from dipole sources, a three-dimensional optical chain can be constructed and manipulated with optimized structure through a reversing field radiated from an electric–magnetic dipole array. A four-bubble chain is illustrated and discussed as an example. This dipolar-shaped focus field may find applications in multiple-particle trapping, delivering and assembly.
41 citations
TL;DR: In this Letter, a hybrid metallic lens that consists of alternating spiral triangle array and spiral slot is designed to improve the plasmonic coupling efficiency.
Abstract: The spin dependence of the focusing behavior of a spiral slot plasmonic lens can be utilized for a miniature circular polarization analyzer. However, the azimuthal polarization component of the incident circular polarization does not contribute to surface plasmon excitation and focusing because it is TE polarized with respect to the spiral slot. In this Letter, a hybrid metallic lens that consists of alternating spiral triangle array and spiral slot is designed to improve the plasmonic coupling efficiency. The spiral triangle array is responsible for coupling the azimuthal polarization component into surface plasmon. Numerical studies show that the field enhancement at the focus and power conversion efficiency can be increased by 39.53% and 94.69% compared to that of pure spiral slot plasmonic lens.
40 citations
TL;DR: The highly directional circularly polarized photon emission from such optically coupled spiral antenna may find important applications in single molecule sensing, quantum optics information processing and integrated photonic circuits as a nanoscale spin photon source.
Abstract: Coupling nanoscale emitters via optical antennas enables comprehensive control of photon emission in terms of intensity, directivity and polarization. In this work we report highly directional emission of circularly polarized photons from quantum dots coupled to a spiral optical antenna. The structural chirality of the spiral antenna imprints spin state to the emitted photons. Experimental results reveal that a circular polarization extinction ratio of 10 is obtainable. Furthermore, increasing the number of turns of the spiral gives rise to higher antenna gain and directivity, leading to higher field intensity and narrower angular width of emission pattern in the far field. For a five-turn Archimedes’ spiral antenna, field intensity increase up to 70-fold simultaneously with antenna directivity of 11.7 dB has been measured in the experiment. The highly directional circularly polarized photon emission from such optically coupled spiral antenna may find important applications in single molecule sensing, quantum optics information processing and integrated photonic circuits as a nanoscale spin photon source.
34 citations
TL;DR: Through appropriate spatial arrangement of an array of triangles, a highly confined focal spot beyond the diffraction limit can be achieved at the geometric center under azimuthally polarized excitation with field enhancement comparable to a bull's eye plasmonic lens under radially polarized illumination.
Abstract: Owing to a geometric phase effect, an isosceles triangular aperture etched into thin metal film leads to constructive or destructive interference of surface plasmons excited at the two equal sides under linearly polarized illumination. Through appropriate spatial arrangement of an array of triangles, a highly confined focal spot beyond the diffraction limit can be achieved at the geometric center under azimuthally polarized excitation with field enhancement comparable to a bull’s eye plasmonic lens under radially polarized illumination. Through simply rotating the orientation of each triangle aperture by 90°, the plasmonic structure defocuses the same azimuthal polarization illumination due to destructive interference caused by a geometric π-phase difference between the two sides of the triangle and between the adjacent triangles.
29 citations
TL;DR: Numerical and experimental studies reveal that the energy distribution on the plasmonic lens surface is determined by the absolute value of the total AM, which gives direct evidences that SPPs can be encoded with the photonic SAM and OAM information simultaneously and the spin degeneracy of the photons can be removed using the interactions between photonic OAM and plasMonic lens.
Abstract: Both spin angular momentum (SAM) and orbital angular momentum (OAM) can be used to carry information in classical optics and quantum optics. In this paper, the encoding of angular momentum (AM) information of photons onto surface plasmon polaritons (SPPs) is demonstrated using a nano-ring plasmonic lens. Near-field energy distribution on the metal surface is measured using a near-field scanning optical microscope (NSOM) when the plasmonic lens is excited by photons with different combinations of SAM and OAM. It is found that both the SAM and OAM can influence the near field energy distribution of SPPs. More interestingly, numerical and experimental studies reveal that the energy distribution on the plasmonic lens surface is determined by the absolute value of the total AM. This gives direct evidences that SPPs can be encoded with the photonic SAM and OAM information simultaneously and the spin degeneracy of the photons can be removed using the interactions between photonic OAM and plasmonic lens. The findings are useful not only for the fundamental understanding of the photonic AM but also for the future design of plasmonic quantum optics devices and systems.
29 citations
TL;DR: This is a reply to the comment by Iglesias and Sáenz directed to a previous paper "Trapping metallic Rayleigh particles with radial polarization," by Q. Zhan.
Abstract: This is a reply to the comment by Iglesias and Saenz directed to a previous paper "Trapping metallic Rayleigh particles with radial polarization," by Q. Zhan, Opt. Express 12, 3377 (2004).
28 citations
TL;DR: The circularly polarized vortex emission from such optically coupled spiral antenna also has high directivity, which may find important applications in quantum optical information, single molecule sensing, and integrated photonic circuits.
Abstract: We analytically and numerically study the emission properties of an electric dipole coupled to a plasmonic spiral structure with different pitch. As a transmitting antenna, the spiral structure couples the radiation from the electric dipole into circularly polarized emitted photons in the far field. The spin carried by the emitted photons is determined by the handedness of the spiral antenna. By increasing the spiral pitch in the unit of surface plasmon wavelength, these circularly polarized photons also gain orbital angular momentum with different topological charges. This phenomenon is attributed to the presence of a geometric phase arising from the interaction of light from point source with the anisotropic spiral structure. The circularly polarized vortex emission from such optically coupled spiral antenna also has high directivity, which may find important applications in quantum optical information, single molecule sensing, and integrated photonic circuits.
23 citations
TL;DR: The spin-dependent plasmonic focusing properties of a spatially arranged triangular sub-aperture array and a hybrid spiral plAsmonic lens are demonstrated using a collection mode near field scanning optical microscope and the coupling efficiency is improved.
Abstract: A hybrid spiral plasmonic lens that consists of alternating spiral slot and spiral triangular sub-aperture array can differentiate circular polarization of different handedness and enable a miniature circular polarization analyzer design with high efficiency. The improved performance compared to pure spiral slot lens comes from the fact that the hybrid lens is capable of focusing both the radial and the azimuthal polarization components of a circular polarization, doubling the coupling efficiency. In this paper, the spin-dependent plasmonic focusing properties of a spatially arranged triangular sub-aperture array and a hybrid spiral plasmonic lens are demonstrated using a collection mode near field scanning optical microscope. The coupling efficiency could be further improved through optimizing the geometry of the hybrid lens.
17 citations
TL;DR: A pixelated one-dimensional photonic band gap structure was designed to enhance both transverse electric and transverse magnetic polarizations through a spatially multiplexed photonic crystal resonance.
Abstract: Fluorescence enhancement using photonic crystals can produce a significant improvement in the signal-to-noise ratio for single molecule and low molecule-concentration fluorescence imaging in biological and biochemical studies. In this Letter, a pixelated one-dimensional photonic band gap structure was designed to enhance both transverse electric and transverse magnetic polarizations through a spatially multiplexed photonic crystal resonance. The average enhancement of 15.6 and 17.9 fold were experimentally verified for the transverse and longitudinal fields on the same substrate. This device may be used as an optical platform for molecular orientation determination.
13 citations
TL;DR: By propagating beamlets from a periodically placed array of single-mode fiber amplifiers in a large mode-are (LMA) fiber, this article found that a self-image of the initial beamlets is formed at certain distances in the LMA fiber.
Abstract: By propagating beamlets from a periodically placed array of single-mode fiber amplifiers in a large mode-are (LMA) fiber, we find that a self-image of the initial beamlets is formed at certain distances in the LMA fiber. A Talbot mirror fiber device (TMFD) based on this property is proposed for phase-locking of a multi-fiber laser. For this laser system, we investigate how the LMA fiber length variation; the fiber amplifier phase variation, amplitude variation, and displacement affect the self-image qualities and the coupling efficiency.
26 Nov 2012
TL;DR: In this article, a novel metamaterial enhanced photonic RF receiver is presented, which consists of a D-ring structure designed on an electro-optic LiNbO 3 substrate to achieve direct modulation of RF signal into optical sideband.
Abstract: The development of a novel metamaterial enhanced photonic RF receiver is presented. The receiver consists of a D-ring structure designed on an electro-optic LiNbO 3 substrate to achieve direct modulation of RF signal into optical sideband. The optimized D-ring design provides strong electric field confinement, thereby resulting in significant improvement in detection sensitivity. Theoretical modeling, design, and optimization are performed to obtain optimal designs. Fabrication and characterization are followed to validate the proposed the design capable of over 10dB improvement in sensitivity. The proposed device demonstrates comparable sensitivity with conventional traveling wave EO modulator scheme with remarkable small aperture size, i.e., λ/25.
TL;DR: A hybrid plasmonic lens with alternating spiral slot and spiral triangle array focuses left-handed and right-handed circular polarization into spatially separated PLASmonic fields, which may serve as a high efficiency circular polarization analyzer as mentioned in this paper.
Abstract: A hybrid plasmonic lens with alternating spiral slot and spiral triangle array focuses left-handed and right-handed circular polarization into spatially separated plasmonic fields, which may serve as a high efficiency circular polarization analyzer.
TL;DR: In this article, the authors review some of the latest works on plasmonic antennas and their interactions with photonic angular momentum and show that the emitted photons can be imprinted with the photonic spin angular momentum.
Abstract: In this invited paper, we review some of our latest works on plasmonic antennas and their interactions with photonic
angular momentum. As receiving antennas, both theoretical and experimental results reveal that spiral plasmonic
antenna responds differently to photons with left-hand circular polarization and right-hand circular polarization. This
spin degeneracy removal finds many potential applications including extremely small circular polarization analyzer for
polarimetric imaging, parallel near field probes for optical imaging and sensing, nano-lithography and high density heat assisted magnetic recording. On the transmitter side, through coupling quantum dot nano-emitters to spiral plasmonic antenna, nano-scale spin photon sources with high directivity and circular polarization extinction ratio is demonstrated. Numerical modeling and experimental evidences also indicate that the emitted photons can be imprinted with the photonic spin angular momentum and orbital angular momentum information simultaneously via the interactions between photonic angular momentum and plasmonic antennas. These findings not only are useful for the fundamental understanding of the interaction between plasmonic antennas and photonic angular momentum but also illustrate the versatility of plasmonic antennas as building blocks for practical spin optics and quantum optics devices and systems.
20 Feb 2012
TL;DR: An electro-optic switch based on a Fabry-Perot resonator design was fabricated and tested in this article, which is comprised of two high index glass substrates with indium tin oxide (ITO) coated Bragg mirrors.
Abstract: An electro-optic (EO) switch based on a Fabry-Perot resonator design was fabricated and tested The switch is comprised
of two high index glass substrates with indium tin oxide (ITO) coated Bragg mirrors, surrounding an electro-optic
polymer layer The ITO top layers were patterned, the electro-optic polymer, SEO100 (Soluxra Inc), was spun coat onto
each of the two Bragg substrates, and the two samples were wafer bonded The sandwich device was then electric field
poled using a field between 80 and 90 V/μm in order to induce a second-order nonlinear optical activity in the electrooptic
polymer The experimental results done at 131 micron laser wavelength with a drive voltage of ±200 volts yielded
a modulation depth of around 86% and 80% for frequencies of 1kHz and 10kHz, respectively