Explanipedia

Topological photonic crystal fiber Open

Bofeng Zhu, Kevin Hean, Stephan Wong, Yuxi Wang, Rimi Banerjee , et al. · 2025

Photonic crystal fibers (PCFs) provide a versatile platform for various applications, thanks to the flexibility with which light guiding can be customized by modifying the fiber geometry. We realize a PCF with guided modes produced by phot…

Effective gain spectra vary the pulses spectrum in a mode-locked cavity Open

Xun Xie, Wonkeun Chang · 2025

Filters typically play a crucial role in generating solitons by strictly confirming the working wavelength in a mode-locked laser. However, we have found that the broad smoothing filter with saturable gain also helps to regulate the pulses…

Switchable nonlinear optical isolator in MXene Open

Yueqiu Hu, Ruhai Bai, Charu Goel, Wonkeun Chang · 2025

We investigate the microdynamics of MXene (Ti3C2Tx) flakes under the influence of two opposing effects: light-induced alignment and Brownian motion. The interplay between these effects gives rise to spatial self-phase modulation patterns. …

Selective tumor ablation via femtosecond laser resonant with collagen Open

Dunxiang Zhang, X. Huang, Xuemei Yang, Xia Ning, Kan Tian , et al. · 2025

The selective laser ablation of pancreatic ductal adenocarcinoma (PDAC), which is an aggressive and highly lethal solid tumor, is of great significance. However, existing thermal ablation methods such as radiofrequency, microwave, and lase…

G-Core: A Simple, Scalable and Balanced RLHF Trainer Open

Junyu Wu, Wonkeun Chang, Xiaotao Liu, Guojian He, Haokai Hong , et al. · 2025

Reinforcement Learning from Human Feedback (RLHF) has become an increasingly popular paradigm for training large language models (LLMs) and diffusion models. While existing RLHF training systems have enabled significant progress, they ofte…

Electrically tunable ferroelectric NbOBr2-integrated nonlinear photonics Open

Sang Hoon Chae, Xiangxin Gong, Ruihuan Duan, Yuhui Yang, Jinpeng Huo , et al. · 2025

Niobium oxide dihalides such as NbOCl2, featured by vanishing interlayer electronic coupling, present thickness-scalable strong second-harmonic generation (SHG), which has demonstrated their compelling performance of free-space nonlinear o…

Selective tumor ablation via femtosecond laser resonant with collagen Open

Dunxiang Zhang, X. Huang, Xuemei Yang, Xia Ning, Kan Tian , et al. · 2025

The selective laser ablation of pancreatic ductal adenocarcinoma (PDAC) which is an aggressive and highly lethal solid tumor is of great significance. However, existing thermal ablation methods such as radiofrequency, microwave and laser a…

Controllable multipulsing in a 1 μm dissipative soliton mode-locked laser Open

Piotr Bojęś, Yingchu Xu, Wonkeun Chang, Karol Krzempek · 2025

Stabilized 30 µJ dissipative soliton resonance laser source at 1064 nm Open

Piotr Pokryszka, Yingchu Xu, Wonkeun Chang, Karol Krzempek · 2024

Mid‐Infrared Sensing Using a Hollow–Core Fiber in a Nonlinear Interferometer Open

Thomas Produit, Tanmoy Chakraborty, Ang Deng, Leonid A. Krivitsky, Wonkeun Chang , et al. · 2024

Increasing the interaction path length is a well‐known method for enhancing the sensitivity of the optical detection system. Hollow–core fibers (HCFs) represent a viable alternative to the traditional multi‐path cells offering low optical …

Microjoule‐Level Mid‐Infrared Femtosecond Pulse Generation in Hollow‐Core Fibers (Laser Photonics Rev. 17(6)/2023) Open

Ang Deng, Trivikramarao Gavara, Muhammad Rosdi Abu Hassan, Daiqi Xiong, Md. Imran Hasan , et al. · 2023

Mid-Infrared Femtosecond Pulse Generation in Hollow-Core Fibers In article number 2200882, Ang Deng, Wonkeun Chang, and colleagues present a novel approach to generate high-energy femtosecond pulses in mid-infrared from a gas-filled hollow…

Higher-order rogue-wave fission in the presence of self-steepening and Raman self-frequency shift Open

Amdad Chowdury, Wonkeun Chang, Marco Battiato · 2023

Using the generalized nonlinear Schrödinger equation, we investigate how the effect of self-steepening and Raman-induced self-frequency shift impact higher-order rogue-wave solutions. We observe that each effect breaks apart the higher-ord…

Multi-nested antiresonant hollow-core fiber with ultralow loss and single-mode guidance Open

Yuxi Wang, Wonkeun Chang · 2023

We propose an antiresonant hollow-core fiber design that exhibits ultralow loss and exceptional single modedness at 1.55 µm. In this design, the confinement loss of less than 10 −6 dB m −1 can be obtained with excellent bending performance…

Designing hybrid-guidance large mode area fiber for high-power lasers Open

Charu Goel, Seongwoo Yoo, Wonkeun Chang · 2023

From rogue wave solution to solitons Open

Amdad Chowdury, Wonkeun Chang, Marco Battiato · 2023

Using a generalized nonlinear Schrödinger equation, we investigate the transformation of a fundamental rogue wave solution to a collection of solitons. Taking the third-order dispersion, self-steepening, and Raman-induced self-frequency sh…

Designing Hybrid-Guidance Large Mode Area Fiber for High-Power Lasers Open

Charu Goel, Seongwoo Yoo, Wonkeun Chang · 2023

Higher-order rogue wave fission under the effects of third-order dispersion, self-steepening and self-frequency shift Open

Amdad Chowdury, Wonkeun Chang, Marco Battiato · 2022

Using the generalised nonlinear Schrödinger equation, we investigate how the effect of third-order dispersion, self-steepening, and Raman-induced-self-frequency shift have an impact on the higher-order rogue waves. We observe that individu…

From rogue waves to solitons Open

Amdad Chowdury, Wonkeun Chang, Marco Battiato · 2022

Using a generalized nonlinear Schrödinger equation, we investigate the transformation of a fundamental rogue wave to a collection of solitons. Taking the third-order dispersion, self-steepening, and Raman-induced self-frequency shift as th…

Microjoule-level mid-infrared femtosecond pulse generation in hollow-core fibres Open

Ang Deng, Trivikramarao Gavara, Muhammad Rosdi Abu Hassan, Md. Imran Hasan, Wonkeun Chang · 2022

We demonstrate a fibre-based approach that generates mid-infrared femtosecond pulses in the 3-4 μm spectral region with microjoule-level single pulse energy. This is realised in a piece of gas-filled antiresonant hollow-core fibre that is …

Integration of an anti-resonant hollow-core fiber with a multimode Yb-doped fiber for high power near-diffraction-limited laser operation Open

Huizi Li, Charu Goel, Jichao Zang, Raghuraman Sidharthan, Shaoxiang Chen , et al. · 2022

We proposed and demonstrated mode cleaning in a high-power fiber laser by integrating an anti-resonant hollow-core fiber (AR-HCF) into a multimode laser cavity of an ytterbium (Yb)-doped fiber (YDF). An in-house mode-matched AR-HCF was fus…

Impact of Mode-Area Dispersion on Nonlinear Pulse Propagation in Gas-Filled Anti-Resonant Hollow-Core Fiber Open

Ying Wan, Md. Imran Hasan, Wonkeun Chang · 2022

We numerically investigate the effect of mode-area dispersion in a tubular-type anti-resonant hollow-core fiber by using a modified generalized nonlinear Schrödinger equation that takes into account the wavelength-dependent mode area in it…

Rogue wave fission Open

Amdad Chowdury, Wonkeun Chang · 2021

We investigate the effect of the third-order dispersion on higher-order rogue wave solutions. We find that under the presence of weak perturbation, the higher-order rogue wave breaks apart into its fundamental rogue wave constituents, simi…

Anti-resonant hollow-core fiber fusion spliced to laser gain fiber for high-power beam delivery Open

Charu Goel, Huizi Li, Muhammad Rosdi Abu Hassan, Wonkeun Chang, Seongwoo Yoo · 2021

We present the selective excitation of the fundamental mode in an anti-resonant hollow-core fiber (ARHCF) fusion-spliced with a commercial large mode area (LMA) fiber. By designing and fabricating a single-ring ARHCF that is mode-matched t…

Understanding bending-induced loss and bending-enhanced higher-order mode suppression in negative curvature fibers Open

Yuxi Wang, Wonkeun Chang · 2021

We present a numerical analysis on bending-induced loss and bending-enhanced higher-order mode suppression in negative curvature fibers. We provide underlying mechanisms on how geometrical parameters affect the bending properties. We find …

Geometrical Scaling of Antiresonant Hollow-Core Fibers for Mid-Infrared Beam Delivery Open

Ang Deng, Wonkeun Chang · 2021

We numerically investigate the effect of scaling two key structural parameters in antiresonant hollow-core fibers—dielectric wall thickness of the cladding elements and core size—in view of low-loss mid-infrared beam delivery. We demonstra…

Effect of decreasing pressure on soliton self-compression in higher-order modes of a gas-filled capillary Open

Ying Wan, Wonkeun Chang · 2021

We numerically investigate soliton self-compression in the higher-order modes of a gas-filled capillary with decreasing pressure. We demonstrate four times enhancement in the compression with the decreasing pressure compared to the equival…

Analyzing mode index mismatch and field overlap for light guidance in negative-curvature fibers Open

Ang Deng, Imran Hasan, Yuxi Wang, Wonkeun Chang · 2020

We numerically investigate the role of cladding geometries in two widely used anti-resonant hollow-core fiber designs with negative curvatures, the tubular negative-curvature fiber and ice-cream-cone negative-curvature fiber. The confineme…

Investigation of a Bragg Grating-Based Fabry–Perot Structure Inscribed Using Femtosecond Laser Micromachining in an Adiabatic Fiber Taper Open

Aayush Madan, Stephanie Hui Kit Yap, Varghese Paulose, Wonkeun Chang, Perry Ping Shum , et al. · 2020

This paper presents the fabrication of a fiber Bragg grating (FBG)-based Fabry–Perot (FP) structure (7 mm total length) in an adiabatic fiber taper, investigates its strain and temperature characteristics, and compares the sensing characte…

Effect of the second ring of antiresonant tubes in negative-curvature fibers Open

Yuxi Wang, Md. Imran Hasan, Muhammad Rosdi Abu Hassan, Wonkeun Chang · 2019

We present a numerical investigation on the effect of introducing the second ring of antiresonant tubes on the guiding properties of the negative-curvature fiber. We determine the range of structural parameters for achieving the optimum li…

Midinfrared Pulse Generation by Pumping in the Normal-Dispersion Regime of a Gas-Filled Hollow-Core Fiber Open

Md. Imran Hasan, Nail Akhmediev, Arnaud Mussot, Wonkeun Chang · 2019

We demonstrate, numerically, the generation of supercontinuum using a high-power ultrafast source at 1.06-μm wavelength and a nonlinear hollow-core fiber. We yield a system that is less sensitive to noise by pumping in the normal-dispersio…

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