한상윤 교수

Fast optical circuit switches (OCSs) with high port count offer reconfigurable bandwidth in optical networks and have the potential to significantly increase the performance and efficiency of modern datacenters. In this paper, we report on a new type of integrated OCS that combines silicon photonics with MEMS actuation. The switch is built on a 50 × 50 passive crossbar network with very low optical loss (0.04 dB/crossing). Efficient switching is achieved by a pair of directional couplers with m

We report on 50 × 50 silicon photonic micro-electromechanical-system (MEMS) switches with reduced polarization dependence. The switches make use of two-level waveguide crossbars and MEMS-actuated adiabatic couplers. Simulations indicate that by eliminating all polarization-dependent elements (e.g., waveguide crossings), low polarization-dependent losses (<;1 dB) can be realized. An experimental prototype switch was fabricated by bonding two silicon-on-insulator wafers. A polarization-dependent l

We report on 50×50 MEMS-actuated silicon photonic switches with 16V switching voltage and microsecond switching time. 2,500 MEMS cantilever 1×2 waveguide switches have been integrated on 9mm×9mm chips.

We report on 4x20 silicon photonic MEMS switch that is capable of multicasting. The switch is built on passive optical crossbar network with gap-adjustable directional couplers. The switch has high on-off extinction ratio (59 dB), low insertion loss (< 4.0 dB), small footprint (1.2x4.5 mm²), and fast response (9.8 µs). The switching voltage is 9.6 V and 20 dB bandwidth is 31.5 nm. One-to-two and one-to-four multicast operations are demonstrated.

We report on a 32 × 32 silicon photonic micro-electro-mechanical-system (MEMS) switch with gap-adjustable directional couplers. The switch is fabricated on 200-mm silicon-on-insulator wafers in a commercial complementary metal-oxide-semiconductor (CMOS) foundry. The fabricated device has a maximum on-chip loss of 7.7 dB and an extinction ratio of 50.8 dB. The switching voltage is 9.45 V and the 20-dB bandwidth is 28.7 nm. Our work shows a promising path for mass production of silicon photonic ME

Fast optical-circuit-switches (OCS) having a large number of ports can significantly enhance the performance and the efficiency of modern data centers by actively rearranging network patterns. Commercially available optical switches typically operate with the use of moving mirror arrays. These switches can have port counts exceeding 100x100 and insertion losses lower than a few dBs. However, their switching speeds are typically tens-of-milliseconds which limits their applications in highly dynam

Fast optical circuit switches with large port count will allow flexible bandwidth allocation in datacenter networks by augmenting electrical packet switching. Here we report microsecond speed optical circuit switch with 50x50 port counts implemented on silicon photonics platform using MEMS actuated directional couplers. The switch has fast switching speed (2.5 µs response time), high on-off extinction ratio (25 dB), small footprint (9x9 mm2), and simple fabrication process (3 lithography steps).

Exploiting mechanical movement of surface micromachined waveguides on a passive silicon photonics platform provides scalable opportunities for efficient on-chip manipulation of optical signals in complex photonic integrated circuits for future photonic networks.

We report on monolithic 4×20 silicon photonic MEMS switches capable of multicast functions. The switch has small footprint (1.2×4.5mm2), low optical insertion loss (&lt;4.0dB), fast switching (9.6µs). 1×2 and 1×4 multicasts were successfully demonstrated.

본 연구는 급변하는 사회환경과 다양한 사회문제에 대처하기 위해 협력적 지역사회복지 거버넌스 발전에 시사점을 제공하는 것을 목적으로 한다. 이를 위해 지역사회복지 거버넌스 역할 수행에 있어 우수한 성과를 거둔 것으로 평가받는 지역사회보장협의체와 지역사회복지협의회 4곳의 종사자를 대상으로 인터뷰를 실시하였다. 사례분석 결과, 각 기관은 공통적으로 참여성, 분권화, 책임성이 확보된 거버넌스 구조에 기반한 강점과 역량을 가지고 있는 것으로 나타났다. 동시에 다양한 외부 환경적 어려움과 향후 개선이 필요한 과제들 또한 확인되었다. 연구결과를 토대로 협력적 지역사회복지 거버넌스 구축을 위한 실천적·정책적 함의를 제시하였으며, 본 연구가 지역사회복지 발전과 사회복지 전달체계 개선에 있어 유의미한 기여를 할 것으로 기대한다.

We present a new device platform which defines on-chip chalcogenide waveguide/resonators without directly etching chalcogenide. Using our platform, we have demonstrated chalcogenide ring resonators with record high Q-factor exceeding 1.1x10⁷ which is 10 times larger than previous record on on-chip chalcogenide resonators. A ring cavity is designed and fabricated for Stimulated Brillouin lasing on our platform. Thanks to the high-Q factor, Brillouin lasing with threshold power of 1 mW

We report on a fully tunable Fabry-Pérot cavity on the silicon photonic MEMS having only 10nW static power. Its resonance wavelength is tunable over the full FSR, and its transmissivity is tunable up to 3.8dB.

We have experimentally demonstrated on-chip chalcogenide resonators with Q-factor of 1.1x107 using a new fabrication method which avoids direct etching of chalcogenide film. Low threshold power (12mW) Brillouin laser is implemented using the fabrication method. Also, cascaded lasing up to 3rd stokes have been observed with 42 mW of pump power.

Originally published in Optica on 20 April 2015 (optica-2-4-370)

본 연구는 복지기술 기반 돌봄서비스에 대한 사회 구성원의 세대별 태도와 주요 결정요인을 탐구하고, 이를 둘러싼 구조적 맥락을 심층적으로 분석하였다. 혼합연구방법(mixed methods research)을 활용하여, 1단계에서는 랜덤 포레스트 회귀분석을 통해 복지기술 기반 돌봄서비스에 대한 세대별 태도와 주요 결정요인을 비교 분석하였으며, 2단계에서는 질적 내용분석을 통해 세대별 인식과 경험을 바탕으로 복지기술의 유용성, 접근성, 및 수용성에 대한 구조적 맥락을 심도 있게 살펴보았다. 연구 결과, 전 세대에서 복지기술 기반 돌봄서비스에 대한 긍정적인 태도가 확인되었으나, 세대별로 유의미한 차이가 나타났다. 특히, 베이비붐세대는 다른 세대보다 복지기술의 유용성과 안전성, 성과분배 인식과 같은 요인에 주목하며, 복지기술 기반 돌봄서비스에 대해 가장 실질적인 기대와 우려를 동시에 보였다. 질적 분석 결과는 이러한 태도 차이가 세대별 생애 경험 및 사회적 맥락에서 비롯되었음을 보여주며, 복