TiO2 Nanophotonic Sensors for Efficient Integrated Evanescent Raman Spectroscopy
TiO2 Nanophotonic Sensors for Efficient Integrated Evanescent Raman Spectroscopy
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DOI：
10.1021/acsphotonics.6b00314
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发表时间：
2016-09-01
期刊：
影响因子：
7
通讯作者：
Suntivich, Jin
中科院分区：
文献类型：
--
作者：
Evans, Christopher C.;Liu, Chengyu;Suntivich, Jin
基于波导的消逝拉曼传感器是一种有吸引力的化学检测技术，因为它们结构紧凑，通过微拉曼光谱仪增加了信号，并且具有纳米级的表面灵敏度。为了提高器件的性能，我们在这里实验演示了将基于波导的消逝拉曼传感器的效率比最先进的氮化硅器件提高一个数量级以上的策略。首先，我们使用可见波长(532 nm对785 nm，通常使用)的泵浦来利用拉曼散射截面对波长(-4)的依赖性。其次，我们使用二氧化钛(二氧化钛)，它结合了相对较低的可见光背景发光和高折射率，将光集中在波导表面附近。这些可视泵浦的二氧化钛传感器每输入泵浦功率显示的斯托克斯信号比氮化硅器件多50倍。最后，我们对环形谐振器进行了探索，观察到了峰值频率比等长直波导高30倍的共振斯托克斯辐射。我们将较高的斯托克斯发射归因于泵浦和发射增强的组合，并建议在未来的器件中使用这种方法来增加斯托克斯信号。
Waveguide-based evanescent Raman sensors are an attractive chemical-detection technology due to their compact format, increased signal over micro-Raman spectrometers, and nanoscale surface sensitivity. To improve the device's performance, herein we experimentally demonstrate strategies to increase the efficiency of waveguide-based evanescent Raman sensors over the state-of-the-art silicon-nitride devices by more than an order of magnitude. First, we use pumping at visible wavelengths (532 nm versus 785 nm, which is commonly used) to exploit the Raman cross-section's lambda(-4) dependence. Second, we use titanium dioxide (TiO2), which combines comparatively low visible background luminescence with a high refractive index to concentrate light near the waveguide's surface. These visibly pumped TiO2 sensors display >50X more Stokes signal per input pump power over that of silicon-nitride devices. Lastly, we explore ring resonators and observe on-resonance Stokes emission with peak rates >30x higher than an equivalent length straight waveguide. We attribute the higher Stokes emission to a combination of pump and emission enhancements and propose using this approach to increase the Stokes signal in future devices.