以光學探測磁共振及時間解析螢光光譜研究受表面電漿增強的奈米鑽石單光子輻射

Abstract

鑽石中的氮-空缺中心為大家熟知的室溫單光子源，本研究簡單的將 100 nm 大小的鑽石放置於單晶金膜與一層 5 nm 厚的氧化鋁介電質形成的表面電漿共振腔上方，不需特殊的微結構或共振腔即可增強奈米鑽石單光子發光效率達六倍之多。利用表面電漿可突破繞射極限使電場侷限在 5 奈米厚的介電層之中，而增益發光。經由光子相干量測實驗鎖定單氮-空缺缺陷中心的奈米鑽石後，以時間解析光激螢光量測技術及螢光的飽和激發功率得知其發光增益源自於自發輻射的加快與激發效率的提升兩個原因。並利用模擬及光學探測磁共振探測氮-空缺中心基態的 Zeeman effect 推論氮-空缺中 心方向與平行於金膜時可有最佳的自發輻射增益。此奈米鑽石與金屬-介電層耦合的方法，能輕易地提高鑽石的發光效率，但又不失其單光子特性，在作為量子傳輸量子計算光源方面非常有發展性。

We use the plasmonic nanocavity to enhance the photoluminescence (PL) of N-V center in diamonds, which is a well-known room temperature single photon source. The plasmonic nanocavity does’t have complicated structures, it merely contains a 60 nm single-crystalline gold film and a 5 nm Al2O3 dielectric layer on the top, and it’s convenient that we don’t have to manipulate our nanodiamonds to some specific hot spots, just simply drop the nanodiamond suspension onto the gold films and left to dry . In addition, the enhanced photoluminescence of nanodiamonds up to 6 times when it compares to the case that nanodiamonds on glass. The PL saturation power and lifetime measured by time-resolved photoluminescence spectroscopy indicate the photoluminescence enhancement exists two attributions that one is the excitation enhancement, and the other is the radiative decay rate enhancement. Furthermore, we use optically detected magnetic resonance with Zeeman effect which can deduce the orientation of N-V center in nanodiamonds. With the help of simulation, we can conclude that nanodiamonds with N-V axis parallel to gold films reveal the best enhancement. This metal-dielectric hybrid system can easily enhance diamonds’ photoluminescence, while the single photon character of the emission is maintained.