Yao-Wei Huang
Email Address
elehyw@nus.edu.sg
7 results
Publication Search Results
Now showing 1 - 7 of 7
Publication Continuous angle-tunable birefringence with freeform metasurfaces for arbitrary polarization conversion(American Association for the Advancement of Science, 2020) Shi, Z.; Zhu, A.Y.; Li, Z.; Huang, Y.-W.; Huang, Y.-W.; Chen, W.T.; Qiu, C.-W.; Capasso, F.; ELECTRICAL AND COMPUTER ENGINEERINGBirefringence occurs when light with different polarizations sees different refractive indices during propagation. It plays an important role in optics and has enabled essential polarization elements such as wave plates. In bulk crystals, it is typically constrained to linear birefringence. In metamaterials with freeform meta-atoms, however, one can engineer the optical anisotropy such that light sees different indices for arbitrary-linear, circular, or elliptical-orthogonal eigen-polarization states. Using topology-optimized metasurfaces, we demonstrate this arbitrary birefringence. It has the unique feature that it can be continuously tuned from linear to elliptical birefringence, by changing the angle of incidence. In this way, a single metasurface can operate as many wave plates in parallel, implementing different polarization transformations. Angle-tunable arbitrary birefringence expands the scope of polarization optics, enables compact and versatile polarization operations that would otherwise require cascading multiple elements, and may find applications in polarization imaging, quantum optics, and other areas. © 2020 The Authors.Publication Vertical split-ring resonator based anomalous beam steering with high extinction ratio(Nature Publishing Group, 2015) Hsu, W.-L; Wu, P.C; Chen, J.-W; Chen, T.-Y; Cheng, B.H; Chen, W.T; Huang, Y.-W; Liao, C.Y; Sun, G; Tsai, D.P; ELECTRICAL AND COMPUTER ENGINEERINGMetasurfaces created artificially with metal nanostructures that are patterned on surfaces of different media have shown to possess "unusual" abilities to manipulate light. Limited by nanofabrication difficulties, so far most reported works have been based on 2D metal structures. We have recently developed an advanced e-beam process that allowed for the deposition of 3D nanostructures, namely vertical split-ring resonators (VSRRs), which opens up another degree of freedom in the metasurface design. Here we explore the functionality of beam steering with phase modulation by tuning only the vertical dimension of the VSRRs and show that anomalous steering reflection of a wide range of angles can be accomplished with high extinction ratio using the finite-difference-time-domain simulation. We also demonstrate that metasurfaces made of 3D VSRRs can be made with roughly half of the footprint compared to that of 2D nano-rods, enabling high density integration of metal nanostructures.Publication Vertical split-ring resonator based nanoplasmonic sensor(American Institute of Physics Inc., 2014) Wu, P.C; Sun, G; Chen, W.T; Yang, K.-Y; Huang, Y.-W; Chen, Y.-H; Huang, H.L; Hsu, W.-L; Chiang, H.P; Tsai, D.P; ELECTRICAL AND COMPUTER ENGINEERINGSplit-ring resonators (SRRs) have been the subject of investigation as plasmonic sensors that operate by sensing plasmon resonance shift ?? when exposed to a medium with a refractive index change ?n. However, conventional planar SRRs have their plasmon fields spread into the substrates, reducing accessible sensing volume and its sensing performance. Such a limitation can be eradicated with vertical SRRs in which the plasmon fields localized in SRR gaps are lifted off from the substrate, allowing for greatly enhanced sensitivity. Here, we demonstrate the highest sensitivity among reported SRR-based sensors in optical frequencies. © 2014 Author(s).Publication Versatile total angular momentum generation using cascaded J-plates(OSA - The Optical Society, 2019) Huang, Y.-W.; Rubin, N.A.; Ambrosio, A.; Shi, Z.; Devlin, R.C.; Qiu, C.-W.; Capasso, F.; ELECTRICAL AND COMPUTER ENGINEERINGOptical elements coupling the spin and orbital angular momentum (SAM/OAM) of light have found a range of applications in classical and quantum optics. The J-plate, with J referring to the photon’s total angular momentum (TAM), is a metasurface device that imparts two arbitrary OAM states on an arbitrary orthogonal basis of spin states. We demonstrate that when these J-plates are cascaded in series, they can generate several single quantum number beams and versatile superpositions thereof. Moreover, in contrast to previous spin-orbit-converters, the output polarization states of cascaded J-plates are not constrained to be the conjugate of the input states. Cascaded J-plates are also demonstrated to produce vector vortex beams and complex structured light, providing new ways to control TAM states of light. © 2019 Optical Society of America.Publication Enhancing the modal purity of orbital angular momentum photons(AIP Publishing, 2020) Nape, I.; Sephton, B.; Huang, Y.-W.; Vallés, A.; Qiu, C.-W.; Ambrosio, A.; Capasso, F.; Forbes, A.; ELECTRICAL AND COMPUTER ENGINEERINGOrbital angular momentum (OAM) beams with topological charge ℓ are commonly generated and detected by modulating an incoming field with an azimuthal phase profile of the form exp(iℓϕ) by a variety of approaches. This results in unwanted radial modes and reduced power in the desired OAM mode. Here, we show how to enhance the modal purity in the creation and detection of classical OAM beams and in the quantum detection of OAM photons. Classically, we combine holographic and metasurface control to produce high purity OAM modes and show how to detect them with high efficiency, extending the demonstration to the quantum realm with spatial light modulators. We demonstrate ultra-high purity OAM modes in orders as high as ℓ = 100 and a doubling of dimensionality in the quantum OAM spectrum from a spontaneous parametric downconversion source. Our work offers a simple route to increase the channel capacity in classical and quantum communication using OAM modes as a basis. © 2020 Author(s).Publication Dielectric multi-momentum meta-transformer in the visible(Nature Publishing Group, 2019) Jin, L.; Huang, Y.-W.; Jin, Z.; Devlin, R.C.; Dong, Z.; Mei, S.; Jiang, M.; Chen, W.T.; Wei, Z.; Liu, H.; Teng, J.; Danner, A.; Li, X.; Xiao, S.; Zhang, S.; Yu, C.; Yang, J.K.W.; Capasso, F.; Qiu, C.-W.; ELECTRICAL AND COMPUTER ENGINEERINGMetasurfaces as artificially nanostructured interfaces hold significant potential for multi-functionality, which may play a pivotal role in the next-generation compact nano-devices. The majority of multi-tasked metasurfaces encode or encrypt multi-information either into the carefully tailored metasurfaces or in pre-set complex incident beam arrays. Here, we propose and demonstrate a multi-momentum transformation metasurface (i.e., meta-transformer), by fully synergizing intrinsic properties of light, e.g., orbital angular momentum (OAM) and linear momentum (LM), with a fixed phase profile imparted by a metasurface. The OAM meta-transformer reconstructs different topologically charged beams into on-axis distinct patterns in the same plane. The LM meta-transformer converts red, green and blue illuminations to the on-axis images of “R”, “G” and “B” as well as vivid color holograms, respectively. Thanks to the infinite states of light-metasurface phase combinations, such ultra-compact meta-transformer has potential in information storage, nanophotonics, optical integration and optical encryption. © 2019, The Author(s).Publication Giant intrinsic chiro-optical activity in planar dielectric nanostructures(Springer Nature, 2018) Zhu, A.Y.; Chen, W.T.; Zaidi, A.; Huang, Y.-W.; Khorasaninejad, M.; Sanjeev, V.; Qiu, C.-W.; Capasso, F.; ELECTRICAL AND COMPUTER ENGINEERINGThe strong optical chirality arising from certain synthetic metamaterials has important and widespread applications in polarization optics, stereochemistry and spintronics. However, these intrinsically chiral metamaterials are restricted to a complicated three-dimensional (3D) geometry, which leads to significant fabrication challenges, particularly at visible wavelengths. Their planar two-dimensional (2D) counterparts are limited by symmetry considerations to operation at oblique angles (extrinsic chirality) and possess significantly weaker chiro-optical responses close to normal incidence. Here, we address the challenge of realizing strong intrinsic chirality from thin, planar dielectric nanostructures. Most notably, we experimentally achieve near-unity circular dichroism with ~90% of the light with the chosen helicity being transmitted at a wavelength of 540 nm. This is the highest value demonstrated to date for any geometry in the visible spectrum. We interpret this result within the charge-current multipole expansion framework and show that the excitation of higher-order multipoles is responsible for the giant circular dichroism. These experimental results enable the realization of high-performance miniaturized chiro-optical components in a scalable manner at optical frequencies. © 2018, The Author(s).