Developing novel chip-scale spectrometers for infrared sensing applications

标题：开发用于红外传感的新型芯片规模光谱仪光谱仪是化学和生物传感、材料分析和光源表征中广泛使用的工具。中红外(MID-IR)光谱仪对于传感和成像应用特别重要，因为许多生化分子在中红外频率上有光谱“指纹”。然而，现有中红外光谱仪的大尺寸、重量和成本限制了它们的采用，尽管它们的潜在应用范围很广。在这项工作中，研究人员将利用集成光子学的进步来开发低成本、紧凑和轻便的芯片级中红外光谱仪。芯片规模的中红外光谱仪将利用一种基于“复杂光子结构”的新设计范式，以实现与现有桌面中红外光谱仪相同的性能。芯片规模的中红外光谱仪将有广泛的应用，从污染控制和环境监测的痕量气体传感到燃烧分析和医疗诊断。研究人员将把这项研究与教育结合起来，包括培训研究生和本科生、课程开发和外展活动。高分辨率芯片规模光谱仪的开发可以使便携式、低成本的光谱分析用于现场传感，并增强芯片上实验室的功能。在已开发的不同类型的片上光谱仪中，由于波长长、探测器噪声大，没有一种光谱仪适用于中红外频率。目前的红外光谱仪依靠多路复用优势(即所谓的Fellgett优势)来实现可接受的信噪比。这些光谱仪通过远距离扫描反射镜来工作，这在芯片上很难采用。这项提议的主要目标是开发新型的片上光谱仪，能够利用Fellgett的优势达到中红外传感应用所需的灵敏度水平，同时保持占地面积小、高分辨率、宽带宽和低损耗。研究人员将利用复杂光子结构的独特特性，在有限的占地面积内提供宽带、非共振的光学路径增强，以开发芯片规模的光谱仪。他们提出了三种基于(I)无序结构、(Ii)混沌腔、(Iii)螺旋波导的光谱仪设计，它们提供了不同的光谱分辨率、占地面积和灵敏度，因此针对不同的应用进行了优化。每个光谱仪都由一个复杂的光子结构组成，该结构由一个输入波导和一个输出波导组成。当复杂结构的折射率被调制(例如，通过热光或电光效应)时，记录透射光强度。然后用描述系统对不同波长和折射率的响应的校准数据恢复输入光谱。这种方法可以在不移动元件的情况下实现芯片规模光谱仪中的费尔格特？S优势，同时保持较小的占地面积。无序结构和混沌腔等复杂系统对探测波长和折射率调制的变化具有非常敏感的响应，从而提高了光谱分辨率和工作带宽。最后，通过拟议的工作获得的对具有宽带光程增强的新型光子结构的洞察可以使更多的应用于片上传感和成像。

Title: Developing novel chip-scale spectrometers for infrared sensing applicationsSpectrometers are widely used tools in chemical and biological sensing, material analysis, and light source characterization. Mid-infrared (mid-IR) spectrometers are of particular importance to sensing and imaging applications, since many biochemical molecules have spectral "fingerprints" in the mid-IR frequency. However, the large size, weight, and cost of existing mid-IR spectrometers has limited their adoption despite the broad range of potential applications. In this work, the investigators will leverage advances in integrated photonics to develop chip-scale mid-IR spectrometers which are low-cost, compact, and lightweight. The chip-scale mid-IR spectrometers will utilize a new design paradigm based on "complex photonic structures" to achieve the same performance as the existing tabletop mid-IR spectrometers. The chip-scale mid-IR spectrometers will have wide-spread applications from trace-gas sensing for pollution control and environmental monitoring to combustion analysis and medical diagnostics. The investigators will integrate the research with education including training graduate and undergraduate students, curriculum development and outreach activities. The development of a high-resolution chip-scale spectrometer could enable portable, low-cost spectroscopy for field sensing as well as enhancing lab-on-a-chip functionality. Among the different types of on-chip spectrometers that have been developed, none of them is applicable to the mid-infrared (IR) frequency because of the long wavelength and large detector noise. Current IR spectrometers rely on the multiplex advantage (the so-called Fellgett's advantage) to achieve an acceptable signal-to-noise ratio. These spectrometers operate by scanning a mirror over a long distance, which cannot be easily adopted on-chip. The primary goal of this proposal is to develop novel on-chip spectrometers capable of utilizing the Fellgett's advantage to achieve the level of sensitivity required for mid-IR sensing applications, while maintaining small footprint, high-resolution, broad-bandwidth, and low-loss. The investigators will leverage the unique characteristic of complex photonic structures, which provide broadband, non-resonant enhancement of optical pathlengths in a limited footprint to develop chip-scale spectrometers. They propose three spectrometer designs based on (i) a disordered structure, (ii) a chaotic cavity, (iii) a spiral waveguide, which provide different spectral resolution, footprint and sensitivity, and are therefore optimized for different applications. Each spectrometer consists of a complex photonic structure with a single input waveguide and a single output waveguide. The transmitted light intensity is recorded as the refractive index of the complex structure is modulated (e.g., via the thermo-optic or electro-optic effect). The input spectrum is then recovered with the calibration data describing the system response to different wavelengths and refractive indices. This approach can achieve the Fellgett?s advantage in a chip-scale spectrometer without moving components while maintaining a small footprint. The complex systems such as disordered structures and chaotic cavities can have extremely sensitive response to changes in the probe wavelength and refractive index modulation, thus enhancing the spectral resolution and operation bandwidth. Finally, the insights gained through the proposed work into novel photonic structures with broadband pathlength enhancement could enable additional applications in on-chip sensing and imaging.