arXiv subjects

Hyunchae Chun

Publications and source records attributed to Hyunchae Chun.

3 recordsLinked to original sources

arXiv2026

OAM Light Demultiplexing from an Intensity Profile using Orthogonality Restoration of Pair Modes

Orbital Angular Momentum (OAM) of light is a promising degree of freedom for next-generation communication. By exploiting the orthogonality of OAM modes, multi-channel division enables a linear increase in communication performance proportional to the number of available modes. However, the multiplexing and demultiplexing of each superposition state remain essential yet complex processes. Demultiplexing has been established through spatial-domain methods that require additional optical elements such as gratings and apertures, which can decrease communication efficiency and accuracy under various conditions. In this paper, we propose a demultiplexing method under a single intensity profile by orthogonality restoration of OAM pair states. This method can be applied directly to an OAM multichannel communication system without additional receiver-side optical structure. We present simulation results of our method under various conditions.

physics.optics↗

arXiv2025

OAM spatial demultiplexing by diffraction-based noiseless mode conversion with axicon

The physics of orbital angular momentum (OAM) carrying light has been well-defined since the 1990s. Leveraging its physical phenomena has become a significant focus in various areas of research. For instance, OAM is applied in hybrid free-space optical communication channels, like wavelength division multiplexing. Due to its orthogonality, OAM can be multiplexed and demultiplexed, enabling the use of multiple orthogonal OAM beams to achieve high-capacity optical communication systems. In this appliance, there will be instability of light because its phase distribution is quite complicated. This study focuses on spatial demultiplexing using Computer Generated Holography (CGH) based OAM diffraction. Earlier research on OAM diffraction primarily involved fork gratings. Spatial demultiplexing has phase distribution instability and noise problems in free space optics. Axicons have been studied extensively in the context of perfect vortex generation. Drawing inspiration from these two areas of physics, we propose a noiseless topological charge conversion through axicon properties in spatial demultiplexing using CGH. Furthermore, we estimate the axicon optical approximate solution that is appropriate for research purposes.

physics.optics↗

arXiv2016

Motion-Compensated Handheld Quantum Key Distribution System

Mobile devices have become an inseparable part of our everyday life. They are used to transmit an ever-increasing amount of sensitive health, financial and personal information. This exposes us to the growing scale and sophistication of cyber-attacks. Quantum Key Distribution (QKD) can provide unconditional and future-proof data security but implementing it for handheld mobile devices comes with specific challenges. To establish security, secret keys of sufficient length need to be transmitted during the time of a handheld transaction (~1s) despite device misalignment, ambient light and user's inevitable hand movements. Transmitters and receivers should ideally be compact and low-cost, while avoiding security loopholes. Here we demonstrate the first QKD transmission from a handheld transmitter with a key-rate large enough to overcome finite key effects. Using dynamic beam-steering, reference-frame-independent encoding and fast indistinguishable pulse generation, we obtain a secret key rate above 30kb/s over a distance of 0.5m under ambient light conditions.

quant-ph↗