Yu-Chueh Hung

Electrooptic Polymer Ring Resonator Modulation up to 165 GHz

Modulation is demonstrated at 84, 111, 139, and 165 GHz resonances of a traveling-wave electrooptic polymer ring-resonator-based modulator. The modulation response is characterized throughout the W-band, illustrating the resonant response at 84 and 111 GHz. A traveling-wave analysis that includes the compound effect of microwave loss and optical/microwave velocity mismatch in a ring-resonator-based modulator is presented and shows a good agreement with experimental results. The ring modulator shows superior performance compared to the Mach-Zehnder modulator in the presence of these limitations when both structures have the same equivalent low-frequency Vpi

Photoinduced write-once read-many-times memory device based on DNA biopolymer nanocomposite

We demonstrate a photoinduced write-once read-many-times (WORM) organic memory device based on DNA biopolymer nanocomposite. The device consists of a single biopolymer layer sandwiched between electrodes, in which electrical bistability is activated by in situ formation of silver nanoparticles embedded in biopolymer upon light irradiation. The device exhibits a switching effect to high conductivity above a threshold of 2.6 V and a good retention property. This facile technique, taking advantage of DNA’s affinity for metals and solution processing, can optically manipulate the properties of DNA nanocomposite thin films, which holds promise for optical storage and plasmonic applications.

Well‐Defined Multibranched Gold with Surface Plasmon Resonance in Near‐Infrared Region from Seeding Growth Approach Using Gyroid Block Copolymer Template

Well-defined multibranched gold (Au) in polymers, both as bulk or continuous thin films, can be fabricated by using a nanoporous polymer with gyroid nanochannels as a template. The nanoporous polymer template is obtained from the self-assembly of a degradable block copolymer, polystyrene-b-poly (L-lactide) (PS-PLLA), followed by the hydrolysis of PLLA blocks. Templated seeding growth approach can be conducted to create precisely controlled nanostructured Au giving remarkable surface plasmon resonance (SPR) in (branched Au with uniform distribution in PS matrix) near-infrared (NIR) region. Controlled growth conditions allow the fabrication of three-dimensionally ordered nanoporous Au particles that possess NIR SPR. Double gyroid Au with dual networks in the PS matrix is obtained after completing the seeding growth at which the NIR SPR diminishes resulting from the reduction in the density of nanostructured edge.

Shifting Networks to Achieve Subgroup Symmetry Properties

A simple method for the preparation of nanomaterials with new functionality by physical displacement of a network phase is suggested, giving a change in space group symmetry and hence properties. A double gyroid structure made by the self-assembly of block copolymers is used as a model system for the demonstration of shifting networks to achieve single gyroid-like scattering properties. Free-standing single gyroid-like network materials can be fabricated to give nanophotonic properties, similar to the photonic properties of a butterfly wing structure.

Side-chain electro-optic polymer modulator with wide thermal stability ranging from −46°Cto95°C for fiber-optic gyroscope applications

Electro-optic (EO) polymer modulators with a wide range of thermal stability from −46°Cto95°C for fiber-optic gyroscope applications are reported. The synthesized EO side-chain polymer used has a glass transient temperature (Tg) of 200°C and a large EO coefficient of 25.2pm∕V in a real device measurement. Mach–Zehnder (MZ) intensity and optical phase modulators are implemented based on this high-Tg side-chain EO polymer, exhibiting ∼3.75V half-wave voltage with 1.5cm interaction length and 2.3cm total length at 1.55μm wavelength. The optical fiber-to-lens insertion loss is ∼7.5dB in the MZ interferometers and ∼6dB in the straight waveguides. We examine the long-term thermal stability of these devices and demonstrate their ability to meet the strict requirements of various EO device applications, particularly fiber-optic gyroscopes.

A polymer-based SERS-active substrate with gyroid-structured gold multibranches

Here, we suggest an effective method to create a three-dimensional SERS-active substrate using a nanoporous polymer with bicontinuous nanochannels as a template for electroless plating of gold (Au), resulting in the formation of Au multibranches with sharp tips and corners for high-density and uniformly distributed hotspots as reliable SERS devices for detection. Also, by taking advantage of easy processing of polymeric materials, the polymer-based SERS-active substrate can be effectively fabricated in a large area for device design with mechanical robustness. Crystal violet and β-carotene molecules are used to demonstrate the superior SERS detection sensitivity with high reproducibility and stability using the polymer-based SERS-active substrate, suggesting a new approach to fabricate materials for the detection of chemicals with an average enhancement factor up to 108.

Photobleached refractive index tapers in electrooptic polymer rib waveguides

Photobleached refractive index tapers in electrooptic polymer rib waveguides, which act as two-dimensional optical mode transformers, are investigated. One taper method involves a discrete step mask-shifting scheme with a fixed intensity UV light source. A second method utilizes a gray-scale mask to precisely control the intensity of UV light reaching each portion of the taper. Using a gray-scale mask, adiabatic refractive index tapers can be inscribed into electrooptic polymer waveguides in a single fabrication step with no scanning parts. Optimized taper profiles are derived and applications for their incorporation into passive-to-active waveguide transitions are described.

Plasmon Hybridization and Dipolar Interaction on the Resonances of Helix Metamaterials

Metallic helix metamaterial has been demonstrated to show strong circular dichroism and is promising for photonic applications such as broadband circular polarizers. In this paper, we present the analysis on the resonances of gold helix metamaterials by dipolar interactions and hybridization and discuss the origin of the broadband feature. Coupling effects among induced dipoles in the helices are examined by the current and field distributions of a single-helix metamaterial. Such analysis is also applied to explain the geometry-dependent resonance of a double-helix metamaterial, and optical properties are discussed. Our analysis provides a physical understanding of the resonant behaviors that can guide the design of metallic helix metamaterials and manipulate their resonant properties.

Low threshold amplified spontaneous emission from dye-doped DNA biopolymer

In this study, we investigate the amplified spontaneous emission (ASE) properties and conduct a comparative study for two kinds of dye-doped deoxyribonucleic acid (DNA) biopolymers. The system consists of optical films made of DNA modified by two types of surfactants and doped with a common laser dye rhodamine 6G (Rh6G). The ASE properties of the optical films were characterized by a pulsed Nd:YAG laser. The results show that low threshold of DNA biopolymer can be achieved by the employment of suitable surfactant in the system, resulting from an efficient energy transfer process. Coupled with the fluorescence enhancement exhibited in DNA, this effect can further advance biopolymers toward highly efficient media for lasing applications and organic solid-state lasers.

Polymer-based directional coupler modulator with high linearity

A generalized novel two-section directional coupler modulator with a linear transfer function is presented. This scheme introduces different coupling coefficients for each of the sections. We show that this configuration effectively suppresses the third-order intermodulation distortion compared to a conventional Mach-Zehnder modulator. It can be easily implemented by the photobleaching technique in polymer technology and demonstrates a simple and promising design for high-performance analog optical links without a complicated structure or electrical control.