Research

Nanopatterned Dual-Carbon-Dot Photonic Films with Enhanced Light Outcoupling, G. Jeon, H. Ahn, T. Kim, N. Y. Ha*, Advanced Optical Materials, Vol.14, Issue 33, e716376 (August 19, 2026)
Nanoimprinted carbon-dot/PVA films integrate blue- and green-emissive carbon dots with periodic polymer gratings to achieve directional photoluminescence. Grating-mediated outcoupling controls the emission angle and spectral distribution, offering a scalable route toward carbon-dot-based photonic films and light-emitting devices.

Nanostructure-guided optical anisotropy associated with in-plane dipole orientation in quasi-2D perovskites via nucleation pathway control, K. Han, G. Jeon, H. Yoo, N. Y. Ha*, Nano Energy, Vo. 154, 112017 (May 9, 2026)
Ordered quasi-2D perovskite films on nanopatterned gratings enable highly polarized surface-emitting distributed-feedback lasing. The combination of nucleation-pathway engineering and photonic nanostructuring enhances crystal ordering, optical feedback, and directional green emission, highlighting a scalable route toward solution-processed perovskite nanolasers.

Manipulation of Structural Colors in Liquid-Crystal Helical Structures Deformed by Surface Controls, C. Lim, S. Bae, S. M. Jeong, N. Y. Ha*, ACS Applied Materials & Interfaces, Vol. 10, Issue 14, 120690-120695, (April 11, 2018).
Simultaneous control of the spectral position and bandwidth of structural color is achieved in cholesteric liquid-crystal structures using an amorphous perfluoropolymer alignment layer. The surface-induced deformation of helical structures enables electrically tunable structural colors at relatively low operating voltages compared with conventional cholesteric liquid-crystal systems.

Sol–Gel Substrates with Engineered Multiple Photonic Bandgaps for Full-Color Photonic Devices, S. H. Lee and N. Y. Ha*, Small, Vol. 7, Issue 19, 2704 - 2708 (October 4, 2011) (Frontispiece).
Inorganic sol–gel films with engineered multiple photonic bandgaps are designed using TiO₂, SiO₂, and mixed SiO₂–TiO₂ multilayer structures. Their controllable optical resonances across the visible spectral region enable full-color photonic functionality, including red–green–blue pixelated liquid-crystal laser operation using the sol–gel film as an optical resonator.

Color- and reflectance-tunable multiple reflectors assembled from three polymer films, N. Y. Ha*, S. M. Jeong, S. Nishimura, and H. Takezoe*, Advanced Materials, Vol. 22, Issue 14, 1617 - 1621 (April 12, 2010).
Tunable reflectance and structural colors are achieved across the visible spectral region by controlling the polarization state of incident light. The multiple photonic bandgap reflectors are assembled from an anisotropic polymeric nematic liquid-crystal film and two isotropic polymer films, where the stacking sequence determines the optical response and color-reflection characteristics.

Perfluoropolymer Surface for Shock-free Homeotropic Alignment of Smectic Liquid Crystals, S. M. Jeong, J. K. Kim, Y. Shimbo, F. Araoka, S. Dhara, N. Y. Ha, K. Ishikawa, H. Takezoe*, Advanced Materials, Vol. 22, Issue 1, 34 - 38 (Jan 5, 2010) (Frontispiece).
Shock-free homeotropic alignment of smectic liquid crystals is realized on an amorphous perfluoropolymer surface. The hydrophobic alignment layer enables spontaneous recovery of the original vertical orientation after deformation caused by mechanical shock, such as pressing with tweezers or crystallization, offering a robust surface-control strategy for smectic liquid-crystal systems.

Simultaneous red, green, and blue lasing emissions in a single-pitched cholesteric liquid-crystal system, N. Y. Ha, S. M. Jeong, S. Nishimura, G. Suzaki, K. Ishikawa, and H. Takezoe*, Advanced Materials, Vol. 20, Issue 13, 2503-2507 (July 2 2008).
Simultaneous red, green, and blue lasing emissions are achieved in a single resonator containing a single gain medium under single optical pumping. The cholesteric liquid-crystal resonator is designed with multiple photonic bandgaps, while energy transfer between two fluorescent dyes enables multicolor laser emission from one integrated photonic structure.

Fabrication of a simultaneous red-green-blue reflector using single-pitched cholesteric liquid crystals, N. Y. Ha, Y. Ohtsuka, S. M. Jeong, S. Nishimura, G. Suzaki, Y. Takanishi, K. Ishikawa, and H. Takezoe*, Nature Materials, Vol. 7, Issue 1, 43-47 (January 2008).
A single-pitched cholesteric liquid-crystal structure is engineered to exhibit simultaneous red, green, and blue reflection beyond the conventional one-pitch–one-color relationship. The sophisticated helical architecture enables broadband RGB reflection from a single cholesteric liquid-crystal system, offering a compact strategy for full-color reflective photonic devices.

Self-assembled silica photonic crystal as a liquid crystal alignment layer and its electro-optic application in Fabry-Perot cavity structure, N. Y. Ha, Y. K. Woo, B. Park, H. Takezoe and J. W. Wu*, Advanced Materials, Vol. 16, No. 19, 1725-1729 (4 October 2004) (Inside Cover Picture).
Self-assembled silica photonic-crystal films function as liquid-crystal alignment layers through surface microgrooves, enabling liquid-crystal orientation without additional rubbing or surface treatment. Depending on the relative orientation of the microgrooves, nematic or twisted-nematic alignment can be formed, and electro-optic tuning of Fabry–Perot cavity modes is demonstrated using the photonic-crystal-based cavity structure.

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