https://scholar.dgist.ac.kr/handle/20.500.11750/11777 2026-11-15T15:28:35Z https://scholar.dgist.ac.kr/handle/20.500.11750/61004 Title: Dual-directional interferometric control for post-fabrication wavelength alignment in a silicon photonic bidirectional arrayed waveguide grating Author(s): Vatandoust, Leila; Kim, Jae Hyeon; Gupta, Shashank; 김태연; Tusher, Munirul; Moon, Hyung-Myung; Han, Sangyoon; Merklein, Moritz; Quack, Niels Abstract: Precise wavelength alignment is essential for dense wavelength-division multiplexing (DWDM) systems, where fabrication-induced deviations can lead to channel mismatch and degraded performance. Arrayed waveguide gratings (AWGs) are widely used in silicon photonics DWDM systems; however, their passive nature limits post-fabrication spectral correction, while conventional thermo-optic tuning predominantly produces unidirectional wavelength shifts. Here, we demonstrate a dual-arm interferometric approach for post-fabrication wavelength alignment using a silicon photonic asymmetric Mach-Zehnder interferometer (AMZI)-bidirectional arrayed integrated into both AMZI arms enable dual-directional interferometric control through selective actuation of the long or short interferometer arm. In the fabricated device, an initial wavelength offset of approximately +0.17 nm from the design wavelength of 1527.99 nm is observed. At 1.8 V (29 mW), thermo-optic actuation improves the spectral overlap between the AMZI transfer function and the BiAWG passbands, resulting in a cascaded peak-transmission enhancement of approximately 3-4 dB. Under short-arm actuation at 2.1 V, the measured peak associated with the nominal central channel is observed at 1527.98 nm, bringing the measured wavelength into agreement with the design wavelength of 1527.99 nm within the experimental wavelengthsampling resolution (0.01 nm). The demonstrated dual-directional interferometric control provides a compact post-fabrication calibration approach for compensating fabrication-induced wavelength offsets while enhancing the cascaded transmission through improved spectral overlap between the AMZI transfer function and the BiAWG passbands. 2026-08-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/60980 Title: Silicon photonic MEMS platform-based air-coupled optomechanical ultrasound receiver at 2.8 MHz with an ultra-compact active acoustic sensing area Author(s): Nam, Sangwoo; Kim, Jae Hyeon; Park, Young Jae; Choi, Dongju; Kim, Dong Uk; Guezzi, Nizar; Lee, Sangheon; Seo, Younghoon; Choi, Suyoung; Kim, Myeongchan; Seong, Hyojin; Lee, Changho; Ahn, Changmin; Kim, Jungwon; Yu, Jaesok; Han, Sangyoon Abstract: High-resolution non-contact non-destructive evaluation (NDE) utilizing MHz-range ultrasound in air-coupled environments faces two significant challenges: severe signal attenuation and reduced sensitivity due to transducer miniaturization. Optical ultrasound sensors have emerged as promising candidates to overcome these limitations; however, widespread adoption remains challenging. Conventional discrete optical sensors are limited by complex fabrication and rigid form factors. Furthermore, the efforts to implement these on photonic integrated circuits (PICs)-while addressing scalability-are typically constrained by limited sensitivity. To address these requirements, we report a chip-scale optomechanical ultrasound receiver implemented, for the first time, on a silicon photonics MEMS platform. This platform facilitates CMOS-compatible scalability and design freedom to independently optimize mechanical components and optical sensitivity. Consequently, the receiver demonstrates a compact active acoustic sensing area of 4 & times; 10-4 mm2. Despite this size reduction, in the noise-equivalent pressure (NEP)-active-area comparison, the proposed receiver's measured and estimated NEP values are positioned within a range comparable to or lower than those for previously reported air-coupled optical and CMUT sensors, when interpreted relative to the ideal area-scaling trend. Designed for a 2.8 MHz mechanical resonance, the receiver was benchmarked against a commercial 1 MHz air-coupled PZT transducer to provide a practical, controlled experimental baseline. In this controlled experimental comparison, the receiver showed a more than 25,000-fold higher received response per unit active acoustic area than the PZT baseline, serving as a complementary metric for unit-area received response and structural scaling potential. These findings suggest that the silicon photonic MEMS platform can provide a route toward compact, dense-array-compatible optical ultrasound receivers for localized air-coupled sensing. 2026-08-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/58572 Title: MEMS Actuators for Tunable Waveguide Devices in Photonic Integrated Circuits: A Brief Review Author(s): Choi, Dongju; Park, Young Jae; Her, Man Jae; Han, Sangyoon Abstract: Microelectromechanical systems (MEMS)-based tuning methods offer promising solutions for dynamically controlling optical properties in photonic integrated circuits (PICs) to address the limitations associated with traditional approaches that rely on direct modulation of the material’s refractive index. Conventional methods such as thermo-optic, plasma dispersion, and electro-optic modulation, face significant challenges including high energy consumption, limited refractive index change, and issues with heat dissipation and optical losses. By contrast, MEMS-based actuators directly reposition optical components, enabling reduced device footprints, negligible static power consumption, rapid response times, and improved reliability. This paper systematically explores the operating principles and design characteristics of five representative MEMS actuator technologies widely used in tunable waveguide devices: In-plane comb-drive actuators, cantilever actuators, gap-reducing actuators, vertical digital actuators, and vertical comb-drive actuators. Each actuator type is analyzed for its distinct advantages and challenges, with considerations such as device compactness, switching speed, voltage requirements, and robustness against reliability issues such as pull-in phenomena and stiction. The insights presented emphasize the substantial potential of MEMS-based tuning methods to advance the scalability, energy efficiency, and performance of next-generation PICs. Continued research into improving actuator performance, including increased operation speed, lower operating voltages, and further miniaturization, will be critical to achieving widespread integration and adoption. 2025-05-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/58241 Title: MEMS 기반 필드 프로그래머블 포토닉 게이트 어레이(FPPGA)의 파라미터 최적화를 위한 시뮬레이션 도구 개발 Author(s): 엄석찬; 오상열; 전영훈; 권혁수; 한상윤; 배영석 Abstract: 필드 프로그래머블 포토닉 게이트 어레이(FPPGA)는 광 회로를 사용자의 목적에 맞게 동적으로 재구성할 수있어, 통신 네트워크, 양자 컴퓨팅, RF 신호 처리 등 다양한 응용 분야에서 활용될 수 있다. 그러나 이러한 다양한 응용에 적용 가능한 프로그래머블 광 회로를 구현하기 위해서는 입출력 단자와 게이트의 수가 증가하게 되고, 그에 따라제어 파라미터의 수도 늘어나게 되다. 그리고, 이와 같은 복잡한 광학 시스템에서 원하는 기능을 구현하기 위한 최적의파라미터를 찾는 것은 어려운 과제이다. 본 연구에서는 MEMS 기반으로 구현 된 FPPGA 를 효과적으로 활용하기 위하여, 해당 구조를 기반으로 역전파 기법을 적용한 파라미터 최적화 시뮬레이션 도구를 개발하였다. 이 시뮬레이션 도구는제작된 FPPGA의 게이트 구조와 1:1로 매핑되어, 사용자의 목적에 맞게 광 회로의 파라미터를 효율적으로 설정할 수있다. 이를 통해 광 신호 라우팅, 주파수 분할 다중화, 신경망 기반 숫자 인식 등 다양한 응용에서 효과적인 파라미터최적화가 가능함을 입증하였다. 본 연구를 통해 우리는 FPPGA의 실용성을 높이고, 전문 지식이 없는 사용자도 효과적으로 활용할 수 있는 FPPGA용 인터프리터 제작의 기반을 마련하였다. Field Programmable Photonic Gate Arrays (FPPGA) can be dynamically reconfigured to meet user objectives, enabling their application in various fields such as communication networks, quantum computing, and RF signal processing. However, implementing programmable optical circuits suitable for such diverse applications requires increasing the number of input/output terminals and gates, which consequently increases the number of control parameters. As a result, finding the optimal parameters to realize desired functionalities in these complex optical systems becomes a challenging task. In this paper, to utilize MEMS-based FPPGA more effectively, we developed a parameter optimization simulation tool that applies backpropagation techniques to their architecture. This simulation tool directly maps onto the gate structure of the fabricated FPPGA, allowing efficient configuration of optical circuit parameters in alignment with user objectives. We demonstrated that effective parameter optimization is achievable in various applications, including optical signal routing, frequency division multiplexing, and neural network-based digit recognition. Our research enhances the practicality of FPPGAs and lays the groundwork for developing an FPPGA interpreter that can be effectively used by users without specialized knowledge. 2025-01-31T15:00:00Z