Research Project

Photonic Crystals

Confinement and manipulation of light in microcavities is important for a wide range of research areas and applications, e.g., cavity quantum electrodynamics or novel light sources in photonic integrated circuits. The confinement of light could be achieved by photonic bandgap effect in photonic crystal, which is periodic arrangement of dielectric media.
We have utilized defect or discontinuity of arrangement and air-hole shape to achieve strong light confinement. We also developed a subwavelength semiconductor photonic crystal laser which can be fabricated using electron-beam lithography and dry etching. Subwavelength laser sources are potentially useful for nanophotonic circuits, on-chip optical interconnects, and pinpoint-accuracy biochemical sensing.




Random/Aperiod structures

Unlike conventional lasers that utilize mirrors or periodic structures to trap light, random lasers rely on the multiple scattering of light in disordered media for optical feedback and light confinement. Especially, photonic amorphous media with short-range structural order can significantly improve photonic properties, leading to unique applications. We presented experimental and numerical studies on lasing in polycrystalline and amorphous photonic structures which have no significant photonic bandgap effect.
A major limitation to device applications of random lasers is the lack of control and reproducibility of the lasing modes, namely, the frequencies and spatial locations of lasing modes are unpredictable, varying randomly from sample to sample. Unlike periodic or quasiperiodic structure, deterministic aperiodic structures lack both translational and rotational symmetries. Different from random structures, deterministic aperiodic structures are defined by the iteration of simple mathematical rules, rooted in symbolic dynamics and prime number theory, which possess very rich spectral features. We anticipate that the study of lasing in pseudorandom DAS can result in the engineering of multifrequency coherent light sources suitable for planar integration with photonic chips.




Nano Plasmonics for high efficent LED

Surface plasmon (SP) modes have attracted the interest of many researchers in the nano-optics field because of their extremely strong field confinement beyond the diffraction limit. In recent years, various plasmonic devices based on SP modes, such as subwavelength lasers, compact waveguides, and biosensors, have been widely investigated because of their ultrasmall mode volume V and relatively high quality factor. In particular, one of the major studies on SP phenomena is about the enhancement of spontaneous emission rate because of the strong ripple effect of SP modes in light-emitting devices.
We investigate the light emitting diode for our living life such as lightning, display, et. al. By optimizing nano pattern on top or bottom of LED, emitted light is efficently extracted from the LED device.




Metasurface

A metasurface is an artificial nanostructured interface that has subwavelength thickness and that manipulates light by spatially arranged meta-atoms-fundamental building blocks of the metasurface. Those meta-atoms, usually consisting of plasmonic or dielectric nanoantennas, can directly change light properties such as phase, amplitude, and polarization. As a derivative of three-dimensional (3D) metamaterials, metasurfaces have been emerging to tackle some of the critical challenges rooted in traditional metamaterials, such as high resistive loss from resonant plasmonic components and fabrication requirements for making 3D nanostructures. In the past few years, metasurfaces have achieved groundbreaking progress, providing unparalleled control of light, including constructing arbitrary wave fronts and realizing active and nonlinear optical effects. This article provides a systematic review of the current progress in and applications of optical metasurfaces, as well as an overview of metasurface building blocks based on plasmonic resonances, Mie resonance, and the Pancharatnam-Berry phase. (from Annual Review of Materials Research 48, 279 (2018)




Photonic topological insulators

Topological ideas in photonics branch from exciting developments in solid-state materials, along with the discovery of new phases of matter called topological insulators. Topological insulators, being insulating in the bulk, conduct electricity on their surface without dissipation or back-scattering, even in the presence of large impurities.Potential practical applications of topological photonics include photonic circuitry that is less dependent on isolators and slow light that is insensitive to disorder. (from Nat. Photonics, 8, 21 (2014)