基于相位调制轴透镜的红外微型光谱仪设计
Design of infrared microspectrometers based on phase-modulated axilenses
AI总结：
本研究设计了基于相位调制轴透镜的红外微型光谱仪平台，兼具高效聚焦、宽波段偏振不敏感等特性，可集成于红外焦平面阵列，实现了纳米级波长分辨能力，为紧凑型红外成像设备增添光谱功能。
摘要：
我们设计并表征了一种基于轴透镜的新型衍射光学平台，该平台可灵活结合高效点聚焦与光栅选频特性，且兼容基于四级相位掩模构型的可扩展自上而下制备工艺。这一特性通过相位调制的紧凑型轴透镜器件实现：与传统菲涅耳透镜相比，该器件可将选定波长的入射辐射同时聚焦在预设位置，且具有更大的焦深。此外，所提出的器件具有偏振不敏感性，在宽光谱范围内保持高聚焦效率。具体而言，本文讨论并表征了设计用于6μm–12μm长波红外（LWIR）波段以及4μm–6μm中波红外（MWIR）波段的调制轴透镜构型。这些器件非常适合单片集成在红外焦平面阵列（IR-FPAs）的衬底层上方，也可用作紧凑型微型光谱仪。我们系统研究了其聚焦效率、光谱响应和串扰比，并验证了在单个平面上多波长聚焦的线性控制能力。我们的设计方法利用瑞利-索末菲（RS）衍射理论，并通过有限元法（FEM）进行了数值验证。最后，我们展示了空间调制轴透镜在实现紧凑型单透镜光谱仪方面的应用。通过优化器件，我们在λ₀=8μm处实现了Δλ=240nm的最小可分辨波长间隔，在λ₀=5μm处实现了Δλ=165nm的最小可分辨波长间隔。所提出的器件为紧凑型成像设备增添了基础光谱分析能力，可应用于从光谱分选到长波红外、中波红外相衬成像与探测等诸多领域。
英文摘要：
We design and characterize a novel axilens-based diffractive optics platform that flexibly combines efficient point focusing and grating selectivity and is compatible with scalable top-down fabrication based on a 4-level phase mask configuration. This is achieved using phase-modulated compact axilens devices that simultaneously focus incident radiation of selected wavelengths at predefined locations with larger focal depths compared to traditional Fresnel lenses. In addition, the proposed devices are polarization insensitive and maintain a large focusing efficiency over a broad spectral band. Specifically, here we discuss and characterize modulated axilens configurations designed for long-wavelength infrared (LWIR) in the $6~μ$m--12~$μ$m wavelength range and in the $4~μ$m--6~$μ$m mid-wavelength infrared (MWIR) range. These devices are ideally suited for monolithic integration atop the substrate layers of infrared focal plane arrays (IR-FPAs) and for use as compact microspectrometers. We systematically study their focusing efficiency, spectral response, and cross talk ratio, and we demonstrate linear control of multi-wavelength focusing on a single plane. Our design method leverages Rayleigh-Sommerfeld (RS) diffraction theory and is validated numerically using the Finite Element Method (FEM). Finally, we demonstrate the application of spatially modulated axilenses to the realization of compact, single-lens spectrometer. By optimizing our devices, we achieve a minimum distinguishable wavelength interval of $Δλ=240nm$ at $λ_0=8μm$ and $Δλ=165nm$ at $λ_0=5μm$. The proposed devices add fundamental spectroscopic capabilities to compact imaging devices for a number of applications ranging from spectral sorting to LWIR and MWIR phase contrast imaging and detection.
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