Alshamrani Naif, Grieco Andrew, Hong Brandon, Fainman Yeshaiahu
Opt Express. 2021 May 10;29(10):15279-15287. doi: 10.1364/OE.424443.
We introduce and experimentally demonstrate a miniaturized integrated spectrometer operating over a broad bandwidth in the short-wavelength infrared (SWIR) spectrum that combines an add-drop ring resonator narrow band filter with a distributed Bragg reflector (DBR) based broadband filter realized in a silicon photonic platform. The contra-directional coupling DBR filter in this design consists of a pair of waveguide sidewall gratings that act as a broadband filter (i.e., 3.9 nm). The re-directed beam is then fed into the ring resonator which functions as a narrowband filter (i.e., 0.121 nm). In this scheme the free spectral range (FSR) limitation of the ring resonator is overcome by using the DBR as a filter to isolate a single ring resonance line. The overall design of the spectrometer is further simplified by simultaneously tuning both components through the thermo-optic effect. Moreover, several ring-grating spectrometer cells with different central wavelengths can be stacked in cascade in order to cover a broader spectrum bandwidth. This can be done by centering each unit cell on a different center wavelength such that the maximum range of one-unit cell corresponds to the minimum range of the next unit cell. This configuration enables high spectral resolution over a large spectral bandwidth and high extinction ratio (ER), making it suitable for a wide variety of applications.
我们介绍并通过实验演示了一种在短波红外（SWIR）光谱中具有宽带宽的小型集成光谱仪，它将一个分插环谐振器窄带滤波器与一个基于分布式布拉格反射器（DBR）的宽带滤波器相结合，该宽带滤波器在硅光子平台上实现。此设计中的反向耦合DBR滤波器由一对用作宽带滤波器（即3.9纳米）的波导侧壁光栅组成。然后，重新定向的光束被馈入用作窄带滤波器（即0.121纳米）的环形谐振器。在该方案中，通过使用DBR作为滤波器来隔离单个环形谐振线，克服了环形谐振器的自由光谱范围（FSR）限制。通过热光效应同时调谐这两个组件，进一步简化了光谱仪的整体设计。此外，几个具有不同中心波长的环形光栅光谱仪单元可以级联堆叠，以覆盖更宽的光谱带宽。这可以通过将每个单元电池以不同的中心波长为中心来实现，使得一个单元电池的最大范围对应于下一个单元电池的最小范围。这种配置在大光谱带宽上实现了高光谱分辨率和高消光比（ER），使其适用于各种应用。
