arXiv subjects

Hoo-Cheol Lee

Publications and source records attributed to Hoo-Cheol Lee.

3 recordsLinked to original sources

arXiv2023

High harmonic generation from a subwavelength dielectric resonator

Higher-order optical harmonics entered the realm of nanostructured solids being observed recently in optical gratings and metasurfaces with a subwavelength thickness. Structuring materials at the subwavelength scale allows for resonant enhancing of the efficiency of nonlinear processes and reducing the size of high-harmonic sources. Here we report the observation of up to a seventh harmonic generated from a single subwavelength resonator made of AlGaAs material. This process is enabled by careful engineering of the resonator geometry for supporting optical modes associated with a quasi-bound state in the continuum in the mid-infrared spectral range at around λ=3.7 μm pump wavelength. The resonator volume measures ~ 0.1 λ^3. The resonant modes are excited with an azimuthally polarized tightly focused beam. We evaluate the contributions of perturbative and non-perturbative nonlinearities to the harmonic generation process. Our work proves the possibility to miniaturize solid-state sources of high harmonics to the subwavelength volumes.

physics.optics↗

arXiv2023

Enhanced five-photon photoluminescence in subwavelength AlGaAs resonators

Multiphoton processes of absorption photoluminescence have enabled a wide range of applications including three-dimensional microfabrication, data storage, and biological imaging. While the applications of two-photon and three-photon absorption and luminescence have matured considerably, higher-order photoluminescence processes remain more challenging to study due to their lower efficiency, particularly in subwavelength systems. Here we report the observation of it five-photon luminescence from a single subwavelength nanoantenna at room temperature enabled by the Mie resonances. We excite an AlGaAs resonator at around 3.6 um and observe photoluminescence at around 740 nm. We show that the interplay of the Mie multipolar modes at the subwavelength scale can enhance the efficiency of the five-photon luminescence by at least four orders of magnitude, being limited only by sensitivity of our detector. Our work paves the way towards applications of higher-order multiphoton processes at the subwavelength scales enabled by the physics of Mie resonances.

physics.optics↗

arXiv2021

Electrically driven strain-induced deterministic single-photon emitters in a van der Waals heterostructure

Quantum confinement in atomically-thin TMDCs enables the realization of deterministic single-photon emitters. The position and polarization control of single photons have been achieved via local strain engineering using nanostructures. However, most existing TMDC-based emitters are operated by optical pumping, while the emission sites in electrically pumped emitters are uncontrolled. Here, we demonstrate electrically driven single-photon emitters located at the positions where strains are induced by atomic-force-microscope indentation on a van der Waals heterostructure consisting of graphene, hexagonal-boron nitride, and tungsten diselenide. The optical, electrical, and mechanical properties induced by the local strain gradient were systematically analyzed. In particular, single-photon emission was observed at the indentation sites at 4 K. The emission exhibits photon anti-bunching behavior with a g(2)(0) value of ~0.3, intensity saturation and a linearly cross-polarized doublet. This robust spatial control of electrically driven single-photon emitters will pave the way for the practical implementation of integrated quantum light sources.

cond-mat.mes-hall↗