*** You all are welcome to join !!!

Ultrathin Photonic Membrane for 2D Material Light–Matter Interaction

Dr. Ya-Lun HO

Research Center for Electronic and Optical Materials National Institute for Materials Science (NIMS), Japan

12/24(三)10:30～11:30     R546, Engineering Building 5, NYCU (GuanFu Campus) 工程五館5樓546室

※Host : Prof. Guo-En Chang 張國恩教授 (Department of Microelectronics)

Abstract:

Atomic-layer and two-dimensional (2D) materials show great promise for controlling light–matter interactions at the atomic scale. However, their ultrathin geometry limits the interaction volume and reduces optical coupling. To fully realize their potential, photonic structures that concentrate light into atomic-scale regions with minimal loss are required. Here, an ultrathin freestanding photonic membrane tailored for integrating atomic-layer and 2D materials is introduced. Owing to its substrate-free geometry, the membrane provides strong field confinement, restores out-of-plane symmetry, and suppresses radiative leakage. The design also enables Å-level tuning of high-Q resonances, where even a single ALD cycle produces a clearly measurable shift, demonstrating sensitivity to atomic-scale dielectric thickness variations.

Due to the strong field confinement and substrate-free geometry, the membrane effectively serves as a platform for transition metal dichalcogenide (TMD) monolayers such as WS₂, WSe₂, and MoS₂, enabling their excitonic and nonlinear responses to couple efficiently to the membrane resonances. The membrane supports quasi-bound states in the continuum (quasi-BICs) that confine light around the monolayer and enhance exciton–photon coupling, resulting in clear increases in photoluminescence and second-harmonic generation (SHG) across a large area. The stronger SHG further enables polarization-resolved mapping of crystal orientation and grain boundaries. SHG spectroscopy also reveals several narrow peaks associated with different quasi-BIC modes, confirming resonant nonlinear enhancement on this freestanding membrane and demonstrating Å-level resonance engineering and large-area uniform enhancement—opening pathways toward advanced 2D material nanophotonic, quantum, and nonlinear photonic devices.

*** You all are welcome to join !!!

Ion-beam engineered silicon for room-temperature photodetection and monolithic integration at telecom wavelengths

※Speaker :Dr. Yonder Berencen/ Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, Dresden, Germany

※Host : Prof. Guo-En Chang 張國恩教授 (Department of Microelectronics)

※Date : 2025-10-14 (Tuesday)

※Time : 10:30~11:30am

※Location :R546, Engineering Building 5, NYCU (GuanFu Campus) 工程五館5樓546室

※Abstract: Photonic integrated circuits (PICs) are widely recognized as a cornerstone for next-generation information technologies, offering orders-of-magnitude improvements in transmission speed, bandwidth, and energy efficiency compared to conventional electronics [1]. A critical building block of PICs is the photodetector operating in the optical telecommunication bands (1260-1625 nm), where silicon’s intrinsic transparency has traditionally necessitated hybrid integration of materials such as germanium [2,3]. However, this approach introduces major fabrication and cost challenges that limit scalability.

In this talk, I will present a new strategy that leverages ion-beam engineering of deep-level impurities in silicon to realize a high-performance, all-silicon, waveguide-coupled photodetector operating at room temperature in the telecom C band [4]. By driving dopant concentrations close to the solid- solubility limit, ion implantation enables efficient sub-bandgap absorption while preserving electronic transport properties. The resulting devices achieve a responsivity of 0.56 A/W, an external quantum efficiency of 44.8%, a bandwidth of 2 GHz, and a noise-equivalent power of 4.2×10-10 W/Hz1/2 at 1550 nm, performance metrics that meet the stringent requirements of optical communication systems.

Our results establish ion implantation as a scalable and CMOS-compatible pathway to monolithically integrate telecom-wavelength photodetectors into silicon PICs, addressing a long-standing challenge in silicon photonics. Beyond photodetection, this work illustrates how ion-beam techniques can unlock new functionalities in silicon, opening avenues for photonic quantum technologies and advanced optoelectronic integration.