| 研究分担者 |
後藤 秀樹 日本電信電話株式会社NTT物性科学基礎研究所, 企画, 所長 (10393795)
俵 毅彦 日本大学, 工学部, 教授 (40393798)
尾身 博雄 大和大学, 理工学部, 教授 (50257218)
澤野 憲太郎 東京都市大学, 理工学部, 教授 (90409376)
稲葉 智宏 日本電信電話株式会社NTT物性科学基礎研究所, フロンティア機能物性研究部, 研究員 (90839119)
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| 研究実績の概要 |
The SiN/(ErGd)2O3/SOI strip-loaded waveguides have been optimized towards net optical gain. Er concentration was reduced to ~10^20 cm-3 by changing growth conditions. (ErGd)2O3 layer thickness was increased from 90 to 180 nm. With these efforts, propagation loss of ~2.3 dB/cm and confinement factor of >40% have been achieved. Moreover, optical signal enhancement of ~24 dB/cm has been obtained upon optical pumping, very close to the total loss (~26 dB/cm). This indicates that the active medium has been pumped to transparency and very close to the onset of net gain. Furthermore, it is also found that the population inversion ratio is continuously increased as Er concentration decreases. Therefore, net optical gain is highly expected if Er concentration is reduced further.
For realization of lasers, microring resonators based on the aforementioned waveguides have been demonstrated with high Q-factors (>10^5). Such high Q-factors indicate that the extra loss induced by microring is very small. Therefore, lasers can be readily achieved once net optical gain is obtained.
The fabricated waveguides and resonators have also been characterized at cryogenic temperature (~2.3 K). Ultra-narrow optical absorption and emission peaks (~ 100 GHz), as well as long lifetime (~10 ms) were observed, indicating high crystal quality of the (ErGd)2O3 layer and potentially long coherence time of Er ions. The materials and device structure demonstrated here are therefore also a promising platform for quantum optical devices.
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