송봉식 교수

A photonic nanocavity with a high Q factor of 100,000 and a modal volume V of 0.71 cubic wavelengths, is demonstrated. According to the cavity design rule that we discovered recently, we further improve a point-defect cavity in a two-dimensional (2D) photonic crystal (PC) slab, where the arrangement of six air holes near the cavity edges is fine-tuned. We demonstrate that the measured Q factor for the designed cavity increases by a factor of 20 relative to that for a cavity without displaced air

Photonic crystals (PCs) are optical materials of periodic refractive index, designed to block light of certain wavelengths ( [1][1] – [5][2] ). Artificial defects such as line- and/or point-defects can be introduced into PCs to allow light to be manipulated. Ultrasmall photonic devices, with sizes

Photonic nanocavities with high quality (Q) factors are essential components for integrated optical circuits. The use of crystalline silicon carbide (SiC) for such nanocavities enables the realization of devices with superior properties. We fabricate ultrahigh-Q SiC photonic crystal nanocavities by etching air holes into a 4H-SiC slab that is prepared without using hydrogen ion implantation, which usually causes higher absorption losses. In addition, compared to usual designs, a relatively thin

We demonstrate two-dimensional photonic crystals of silicon carbide (SiC)-a wide bandgap semiconductor and one of the hardest materials-at near-infrared wavelengths. Although the refractive index of SiC is lower than that of a conventional semiconductor such as GaAs or Si, we show theoretically that a wide photonic bandgap, a broadband waveguide, and a high-quality nanocavity comparable to those of previous photonic crystals can be obtained in SiC photonic crystals. We also develop a process for

We theoretically and experimentally investigate the characteristics of a multichannel add/drop filter which utilizes in-plane hetero photonic crystals (IP-HPCs). The structure consists of an in-plane array of photonic crystals with different lattice-constants. Finite-difference time-domain calculations reveal that optimal performance in terms of wavelength resolution and efficiency can be kept almost constant at different wavelengths even though slab thickness is not changed. The multichannel ad

We report transmission and reflection characteristics of in-plane hetero-photonic crystals (IP-HPCs) consisting of two serially connected photonic crystal waveguides with differing lattice constants. We show experimentally and theoretically that the transmission spectrum of the structure corresponds to the transmission frequency range common to both waveguides. Also, there exists a frequency gap where the structure has a guiding mode for one waveguide but not for the neighboring one. Our calcula

The manipulation of photons via artificially introduced line and point defects in photonic crystals is becoming important for various scientific and engineering applications. Here, we propose a concept for realizing high extraction of the photons from a line-defect waveguide to free space through a point-defect cavity in a photonic crystal. A configuration of heterophotonic crystals with different lattice constants is introduced, and the heterostructure interface plays an important role, acting

Silicon carbide (SiC) is a promising optical material for stable and broadband nanophotonics. To date, thin crystalline SiC layers for nanophotonic platforms have been created by ion implantation or growth on other materials, which may cause optical absorption in the SiC layer. We fabricated SiC nanobeam photonic crystal cavities directly from a crystalline (4H) SiC bulk wafer using oblique plasma etching to avoid material-based optical absorptions. The measured quality (Q) factor of the nanobea

We have recently demonstrated the fabrication of ultra-high-Q photonic double-heterostructure nanocavities with Q-factors of almost 1 million and ultra-small modal volumes with dimensions of optical wavelengths. Here, we describe the physical origin of the small modal volume by analysing the (imaginary) dispersion relations of the mode-gap of photonic crystal (PC) waveguides, where the mode-gap effect is the fundamental principle by which photons are confined in the nanocavities. By expanding th

We design and fabricate ultra-high-quality (Q) photonic nanocavities in a symmetrically glass-clad silicon (Si) two-dimensional (2D) photonic crystal (PhC) structure. We theoretically investigate the dependence of the refractive index of the glass on the Q factors for asymmetric and symmetric structures. We show that the index-symmetric distribution of the glass is a critical factor to realize ultrahigh Q factors for glass-clad 2D PhC structures. We fabricate symmetrically glass-clad Si PhC nano

In this letter, we experimentally demonstrate resonant-wavelength control of a series of 16 nanocavities in a two-dimensional photonic crystal slab structure by nanometer-order variation of the lattice constants and air-holes sizes. The cavities show a linear dependence on these parameters, a 1-nm increase of lattice constant or air-hole size leading to 4.2-nm increase or 1.56-nm decrease of the resonant wavelength, respectively. These experimental results are in good agreement with the finite-d

In this paper, we review the fundamentals of heterostructures in two-dimensional photonic-crystal (PC) slabs and demonstrate ultra-high-Q nanocavities, which are key components for the realization of PC devices. Heterostructure PCs (hetero-PCs) consist of multiple PC waveguides with different lattice constants. Here we theoretically demonstrate the selective transmission and reflection characteristics of various hetero-PCs, including photonic-tunnelling structures. On the basis of these traits,

We present comprehensive and quantitative analysis of the effect of structural imperfections on quality (Q)-factors in triangular cross-section nanobeam photonic crystal cavities. We investigated statistically the optical losses due to the various imperfections in the air holes’ positions, radii, alignments, and surface roughness, among other factors. It is revealed that the Q-factor decreases significantly from an ideally designed value due to such imperfections, with the main influence