Chi-O Cho

Samsung (South Korea)

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Heonsu Jeon

Seoul National University

Yeonsang Park

Chungnam National University

Young‐Geun Roh

Samsung (South Korea)

Beomseok Lee

Samsung (United States)

Youngho Choe

Korea University

Hye-Won Kim

Korea Institute of Science and Technology

Joonhee Lee

Korea Research Institute of Standards and Science

Yoon Soo Park

Yonsei University

In Kim

Samsung (South Korea)

Yongjo Park

Advanced Institute of Convergence Technology

Cooperative Institutions

Seoul National University

Samsung (South Korea)

Government of the Republic of Korea

Korea Advanced Institute of Science and Technology

Yonsei University

Korea University

Chungbuk National University

Pohang University of Science and Technology

Samsung Advanced Institute of Technology (South Korea)

Korea Research Institute of Chemical Technology

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Enhanced Light Extraction from Organic Light‐Emitting Diodes with 2D SiO₂/SiN_x Photonic Crystals

Advanced Materials (2003)

Young Rag Y.C. Kim Young Woong Song Chi-O Cho Heonsu Jeon

The introduction of a 2D photonic crystal layer is demonstrated to be an effective way to solve light trapping problems in organic light emitting diodes (OLEDs). The overall effect of the photonic crystal structure on the performance of the OLED is investigated by means of current–voltage–luminance measurements and lifetime tests. A schematic of the structure of the OLED device is shown in the Figure.

Schematic

10.1002/adma.200304857

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Citations (243)

Controlled photonic bandgap tuning in mixed colloidal photonic crystals

Hee Jeong Kim Young‐Geun Roh Yeonsang Park Chi-O Cho Heonsu Jeon

Silica and polystyrene spheres were randomly mixed, and ordered into a densely packed photonic crystal. Reflectance spectrum measurements revealed that the L-point pseudobandgap linearly red-shifts as the polystyrene sphere composition increases.

Polystyrene

Colloidal crystal

10.1364/iqec.2004.ithg21

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Photonic Crystal Slab Waveguides Fabricated by the Combination of Holography and Photolithography

Japanese Journal of Applied Physics (2004)

Chi-O Cho Young‐Geun Roh Yeonsang Park Heonsu Jeon Beomseok Lee

We have fabricated air-bridge type two-dimensional photonic crystal waveguides (2D-PCWs) using two high-throughput processes only: holography and photolithography. Despite the existence of misalignments of a defect line with respect to the air-hole arrays, waveguiding in both straight and 90°-bent PCWs was clearly observed at the wavelength of 1.55 µm. We also estimated the upper bound in propagation loss of our straight PCWs, which was measured to be about 40 cm -1 .

Slab

10.1143/jjap.43.1384

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Citations (33)

GaAs-based near-infrared omnidirectional reflector

Applied Physics Letters (2003)

Yeonsang Park Young‐Geun Roh Chi-O Cho Heonsu Jeon Min Gyu Sung

We introduce a compound-semiconductor-based omnidirectional reflector. A four-layer-pair stack of GaAs/AlAs was grown epitaxially using molecular-beam epitaxy, and was then converted to a GaAs/Al2O3 multilayer stack by selective oxidation of the AlAs layers. The resultant one-dimensional photonic crystal exhibited omnidirectional reflection properties in near-IR wavelength range below 1 μm. Reflectance spectra measured at various incidence angles and polarizations were observed to be in good agreement with theoretically simulated results.

Reflector (photography)

Reflection

Crystal (programming language)

10.1063/1.1569045

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Citations (59)

Extraction efficiency enhancement in GaN-based light emitters grown on a holographically nano-patterned sapphire substrate

Quantum Electronics and Laser Science Conference (2005)

Dongho Kim Chi-O Cho Jaehoon Kim Heonsu Jeon T. Sakong

We observed over two-fold enhancement in light extraction efficiency from GaN-based light emitters grown on a nano-patterned sapphire substrate. Nano-hole array patterns were generated by laser holography, which enabled a large area process with high throughput.

Quantum Efficiency

10.1109/qels.2005.1549101

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Citations (1)

Enhanced light extraction from GaN-based light-emitting diodes with holographically generated two-dimensional photonic crystal patterns

Applied Physics Letters (2005)

Dongho Kim Chi-O Cho Yeong-Geun Roh Heonsu Jeon Yoon Soo Park

We observed a significant enhancement in light output from GaN-based light-emitting diodes (LEDs) in which two-dimensional photonic crystal (PC) patterns were integrated. Two-dimensional square-lattice air-hole array patterns with a period that varied from 300 to 700 nm were generated by laser holography. Unlike the commonly utilized electron-beam lithographic technique, the holographic method can make patterns over a large area with high throughput. The resultant PC-LED devices with a pattern period of ∼500nm had more than double the output power, as measured from the top of the device. The experimental observations are qualitatively consistent with the results of three-dimensional finite-difference-time-domain simulation.

Square lattice

10.1063/1.2132073

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Citations (328)

Photonic Crystal Cavity Lasers Patterned by a Combination of Holography and Photolithography

IEEE Photonics Technology Letters (2007)

Chi-O Cho Joonhee Lee Yeonsang Park Yeong-Geun Roh Heonsu Jeon

Air-bridge-type InGaAsP photonic crystal cavity lasers (PCCLs) have been fabricated by employing a combined lithographic technique of laser holography (LH) and photolithography. Cavities of 4-5 mum in diameter were formed photolithographically on a square-lattice photonic crystal background pattern which was predefined by the LH process. Despite structural imperfections originated from the inevitable pattern misalignment during the combination lithography, 40% or higher of the PCCLs lased. Removal of modal degeneracy due to symmetry breaking, which was confirmed by computer simulations, provided a rationale on this rather unexpected result: the structurally imperfect PCCLs (as defined by our combination lithography) might compete with the so-called perfect PCCLs (as defined by, say, the electron-beam lithography) in terms of cavity Q-factor

Next-generation lithography

Nanoimprint lithography

10.1109/lpt.2007.893903

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Towards nano-waveguides

Current Applied Physics (2003)

Chi-O Cho Young‐Geun Roh Yeonsang Park I Jae-Soong Heonsu Jeon

Waveguide

Realization (probability)

10.1016/j.cap.2003.11.020

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Citations (3)

Photonic crystal slab waveguides fabricated by the combination of holography and microlithography

Conference on Lasers and Electro-Optics (2003)

Chi-O Cho Veong-Geun Roh Heonsu Jeon Jeon Beomseok Lee Hye-Won Kim

Slab

Source

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Photonic crystal band edge laser array with a holographically generated square-lattice pattern

Applied Physics Letters (2005)

Chi-O Cho Jaewook Jeong Joonhee Lee Heonsu Jeon In Kim

We fabricated a photonic band edge laser array based on a two-dimensional square-lattice photonic crystal (PC) slab waveguide using a laser holography (LH) method, instead of the commonly used electron-beam lithography (EBL). The nature of the LH process enabled high-throughput large-area fabrication of band edge lasers. Moreover, the laser performance was comparable to that of reported EBL counterparts. Careful examination of the spectral positions of the observed modes with respect to the calculated photonic band structure identified three main band edge modes as the origins of lasing: M2, X2, and M1. Owing to the gradual change in the air-hole size of the PC, the lasing modes shifted monotonically along the laser array, resulting in an M1 mode span of ∼30nm (centered at 1550nm) over a distance of 5mm.

Square lattice

Yablonovite

10.1063/1.2103422

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Citations (37)