Nanoengineered Functional Structures for Photonic and Microfluidic Applications

Abstract

Owing to their extraordinary ability to interacting with external stimuli as well as their versatile functionalities hardly observed in bulk systems, micro- and nano-scale materials, structures, and phenomena have been the subject of increasing interest from both academia and industry. Many diverse fields including optoelectronics, photonics, bioengineering, and energy conversion have all shown significant increases in utilization of, and need for, micro/nano-scale features. To meet this demand, not only novel manufacturing methodologies, but also underlying physics and design principles are called for.

This thesis work addresses these issues while focusing on three main topics: (1) how certain fundamental nanostructures such as periodic nanopatterned surface, multilayers and charged particle-line can be utilized as functional building blocks for multidisciplinary applications ranging from nanoparticle/biomolecule manipulation to optoelectronics/photonics; (2) how these functional nanoarchitectures can be engineered in a continuous and scalable manner to increase the manufacturing throughput; and (3) the underlying physics and the design principles of these nanostructures in particular application systems.

More specifically, large area, 1D/2D periodic sinusoidal nanopatterned surface based on Dynamic Nano-inscribing (DNI) patterning technique is developed. And its applications to nanoparticle assembly/sorting and light extraction from GaN LED are investigated. By exploiting this sinusoidal nanovoid pattern and geometry-dependent ionic entropy, we successfully realized the size-selectively confinement and patterning of submicron-sized particles over a large area. Moreover, general method of light extraction from trapped modes by using these 1D/2D sinusoidal nanogratings have been developed. We applied our method to flip-chip GaN LED and a further enhancement of the total radiative power in addition to the PSS structures have been observed.

Metal/dielectric multilayer structures are widely used as fundamental building blocks for photonic crystal/metamaterials, color filters and anti-reflection coatings. Here in this work, we are focus on the applications of metal/dielectric multilayers on hyperbolic metamaterials (HMM) and surface-plasmon-coupled light emission from 2D materials and organic light emission materials. For hyperbolic metamaterials, we show that by using thin (~7nm) Al doped Ag metal films, we can dramatically improve the performance as well as the photon density of state (DOS) of the HMM. However, a further discussion on the nonlocal response of electrons in ultrathin (sub-1nm) metal films have been conducted and shows that the nonlocality induced by quantum effects of electrons (degeneracy pressure, diffusion kinetics and tunneling) can dramatically induce the transitions of the photonic topology of the metamaterials and intrinsically limit the DOS. Metal/dielectrics multilayers are also used to study the exciton-plasmon energy transfer and surface plasmon coupled light emission from 2D semi-conductors (WSe2) and organic light emission materials (Super Yellow). Based on one optimized planar multilayer structure we observed an 8 times enhancement of the PL signal. And we applied this concept to OLED structure, enhancement of the efficiency were also observed from SY-based OLEDs.