Photonic Crystals Research in Korea

Heonsu Jeon 한국광학회 2002 Current Optics and Photonics Vol.6 No.3

Lasing at topological edge states in a photonic crystal L3 nanocavity dimer array

Han, Changhyun,Lee, Myungjae,Callard, Sé,golè,ne,Seassal, Christian,Jeon, Heonsu Nature Publishing Group UK 2019 Light, science & applications Vol.8 No.1

<▼1><P>Topological photonics have provided new insights for the manipulation of light. Analogous to electrons in topological insulators, photons travelling through the surface of a topological photonic structure or the interface of two photonic structures with different topological phases are free from backscattering caused by structural imperfections or disorder. This exotic nature of the topological edge state (TES) is truly beneficial for nanophotonic devices that suffer from structural irregularities generated during device fabrication. Although various topological states and device concepts have been demonstrated in photonic systems, lasers based on a topological photonic crystal (PhC) cavity array with a wavelength-scale modal volume have not been explored. We investigated TESs in a PhC nanocavity array in the Su–Schrieffer–Heeger model. Upon optical excitation, the topological PhC cavity array realised using an InP-based multiple-quantum-well epilayer spontaneously exhibits lasing peaks at the topological edge and bulk states. TES characteristics, including the modal robustness caused by immunity to scattering, are confirmed from the emission spectra and near-field imaging and by theoretical simulations and calculations.</P></▼1><▼2><P><B>Shrinking topological state lasers</B></P><P>Tiny lasers that emit light from single nano-sized cavities are becoming possible thanks to exotic photonic features called topological edge states (TESs) on the edges of a cavity array. TESs can steer neatly around obstacles without scattering out; this makes them ideal for navigating the inevitable imperfections that appear when fabricating nanostructures. Heonsu Jeon and co-workers at Seoul National University, Republic of Korea, and Université de Lyon, France, etched patterns of holes a few hundred nanometres apart in photoluminescent wafers, then directed a 1064-nanometre laser to optically excite their sample. They observed an isolated peak of stimulated emission around 1500 nanometres from one cavity, attributed to a TES. This evidence of lasing from sources even smaller than the wavelength of light could enable further minimising of photonic devices and have applications for quantum computing.</P></▼2>

A Highly Tunable and Fully Biocompatible Silk Nanoplasmonic Optical Sensor

Lee, Myungjae,Jeon, Heonsu,Kim, Sunghwan American Chemical Society 2015 NANO LETTERS Vol.15 No.5

<P>Novel concepts for manipulating plasmonic resonances and the biocompatibility of plasmonic devices offer great potential in versatile applications involving real-time and in vivo monitoring of analytes with high sensitivity in biomedical and biological research. Here we report a biocompatible and highly tunable plasmonic bio/chemical sensor consisting of a natural silk protein and a gold nanostructure. Our silk plasmonic absorber sensor (SPAS) takes advantage of the strong local field enhancement in the metal–insulator–metal resonator in which silk protein is used as an insulating spacer and substrate. The silk insulating spacer has hydrogel properties and therefore exhibits a controllable swelling when exposed to water–alcohol mixtures. We experimentally and numerically show that drastic spectral shifts in reflectance minima arise from the changing physical volume and refractive index of the silk spacer during swelling. Furthermore, we apply this SPAS device as a glucose sensor with a very high sensitivity of 1200 nm/RIU (refractive index units) and high relative intensity change.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2015/nalefd.2015.15.issue-5/acs.nanolett.5b00680/production/images/medium/nl-2015-006803_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl5b00680'>ACS Electronic Supporting Info</A></P>

Effects of microlens curvature on the operation of microlens-integrated extended cavity GaN VCSELs

Park, Si-Hyun,Jeon, Heonsu WILEY-VCH Verlag 2004 Physica status solidi. A, Applied research Vol.201 No.12

<P>We have fabricated and characterized an extended cavity GaN-VCSEL device integrated with a micro- lens. Laser performance varied depending on the curvature radius of the integrated microlens. At optimum curvature radius, threshold excitation energy was lowest while slope efficiency was largest. Furthermore, no mode hopping was observed and the laser was operated predominantly in single longitudinal mode. The existence of the optimum curvature radius is attributed to a combined effect of reduced light leak in the lateral direction and light feedback in the near-field regime of Gaussian mode. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>

Over 1 hour continuous-wave operation of photonic crystal lasers

Kim, Sunghwan,Lee, Jeongkug,Jeon, Heonsu The Optical Society 2011 Optics express Vol.19 No.1

<P>We report on the long lifetime (>1 hour) of photonic crystal (PC) lasers under continuous-wave (CW) operation. For stable CW operation, we van-der-Waals-bonded our PC lasers to a novel submount structure consisting of MgF₂-diamond bilayers on silicon substrate, which simultaneously ensures vertical mode confinement and efficient heat spread/dissipation. The combination of a ?-point band-edge mode and butt-end fiber coupling yielded high CW fiber-coupled output power (~200 관W). The results demonstrate that the CW lifetime of PC lasers can be extended to the level for practical applications.</P>

알츠하이머병의 영상 진단을 위한 형광 프로브의 개발

민창호 ( Changho Min ),하헌수 ( Heonsu Ha ),전종호 ( Jongho Jeon ) 한국공업화학회 2021 공업화학 Vol.32 No.1

알츠하이머병은 신경퇴행질환으로 뇌조직에서 발생하는 아밀로이드 베타(amyloid-β, Aβ) 펩타이드의 축적과 응집, 타우 단백질의 초인산화, 고농도의 특정 금속이온 축적에 의해 발병하는 것으로 알려져 있다. 현재까지 효과적인 치료제가 개발되지 못하였기 때문에, 알츠하이머병을 초기에 정확하게 진단하는 기술은 매우 중요하다. 알츠하이머병의 진단을 위해 개발된 다양한 기법 중 형광 프로브를 이용한 알츠하이머병의 바이오마커 영상화는 많은 연구자들의 관심을 받고 있다. 본 리뷰 논문에서는 최근 개발된 알츠하이머병 진단용 형광 프로브의 구조와, 체내 뇌 영상화에의 적용을 소개하고자 한다. 본 논문은 향후 새로운 프로브를 개발하고자 하는 연구자들에게 많은 도움이 될 것으로 기대된다. Alzheimer’s disease (AD), an irreversible degenerative disorder, is associated with accumulation and aggregation of amyloid-β peptides, hyperphosphorylated tau proteins, and high level of metal ions in the brain. Up to date, there is no effective therapeutic agent to stop the progress of the disease and thus early and accurate diagnosis of AD has gained increasing attention in recent years. Among several diagnostic methods, an optical imaging using fluorescent probes is one of the most promising tools to visualize AD biomarkers. In this review, we will introduce fluorescent probes that can be applied to in vivo brain imaging of AD models and also their structure. It is expected that the present review will provide useful information to many scientists in the related research fields.

Simultaneous observation of extended and localized modes in compositional disordered photonic crystals

Kim, Sunghwan,Lee, Jeongkug,Jeon, Heonsu,Callard, Sé,golè,ne,Seassal, Christian,Song, Kyung-Deok,Park, Hong-Gyu American Physical Society 2013 Physical review. A. Atomic, molecular, and optical Vol.88 No.2

GaN Surface-Emitting Laser With Monolithic Cavity-Folding Mirrors

Lee, Jae-Soong,Lee, Joonhee,Jeon, Heonsu IEEE 2007 IEEE photonics technology letters Vol.19 No.5-8

<P>We report on the demonstration of a GaN-based surface-emitting laser (SEL) in a folded-cavity (FC) scheme. Two 45deg-angled sidewall deflectors were monolithically integrated at both the edges of an otherwise conventional InGaN multiple-quantum-well edge-emitting laser structure. Despite a low effective mirror reflectivity of R(<1%), the optically pumped broad-area laser structure produced laser oscillation in the vertical direction with a low threshold pump intensity of ~350kW/cm<SUP>2</SUP>. Computer simulations on the FC, which was based on the finite-difference time-domain method, not only quantified the cavity quality of our FC-SEL device but also suggested methods to lower the laser threshold</P>

Milliwatt-level fiber-coupled laser power from photonic crystal band-edge laser.

Kim, Sunghwan,Ahn, Sungmo,Lee, Jeongkug,Jeon, Heonsu,Regreny, Philippe,Seassal, Christian,Augendre, Emmanuel,Di Cioccio, Lea Optical Society of America 2011 Optics express Vol.19 No.3

<P>We report unprecedentedly high output powers measured from large area two-dimensional square-lattice photonic-crystal band-edge lasers (BELs), patterned by holographic lithography. In order to ensure mechanical rigidity, the BELs were fabricated in an InP-based epilayer bonded onto a fused silica substrate beforehand. The BEL devices, employing the surface-emitting ?-point monopole band-edge mode, provide a fiber-coupled single mode output power as high as 2.6 mW and an external differential quantum efficiency of ~4%. The results of a three-dimensional finite-difference time-domain simulation agree with the experimental observation that the large BELs are beneficial for achieving both high power output and high differential quantum efficiency.</P>

Model calculations for enhanced fluorescence in photonic crystal phosphor.

Min, Kyungtaek,Choi, Yun-Kyoung,Jeon, Heonsu Optical Society of America 2012 Optics express Vol.20 No.3

<P>We propose a novel photonic structure, based on the photonic crystal (PC) effect, which simulations show results in an improved fluorescence efficiency from embedded phosphor. To be specific, the phosphor pumping efficiency can be significantly improved by tuning the pump photon energy to a photonic band-edge (PBE) of the PC phosphor. We have confirmed this theoretically by calculating optical properties of one-dimensional PC phosphor structures using the transfer-matrix method and plane-wave expansion method. For a particular model structure based on a quantum dot phosphor, the fluorescence enhancement factor was estimated to be as high as 6.9 for a monochromatic pump source and 2.2 for a broad bandwidth (20 nm) pump source.</P>