为实现红外光谱仪器的小型化, 通过分析现有小型光谱仪, 提出了一种基于平板波导的小型红外光栅光谱仪的设计方法。 平板波导光谱仪的小型化原理与一般的微小型光谱仪不同。 在平板波导光谱仪中, 光束被限制在一层薄薄的平板波导介质中传播, 看起来像是整个光学系统被压扁了。 在垂直于平板波导的方向上光学元件的尺寸可以做到很小, 从而显著减小光学系统的尺寸。 该系统的设计可分为Czerny-Turner结构设计、 波导结构设计。 先根据像差理论设计Czerny-Turner结构, 目标是保证光谱分辨率及校正像差; 然后根据几何光学理论设计波导结构, 包括平板波导和两个柱面透镜, 目标是压缩光束并校正像散; 最后将它们输入Zemax软件中进行综合优化, 以获得最优的光学系统。 据此方法设计了一个平板波导红外光栅光谱仪, 工作波段为8~12 μm, 数值孔径为0.22, 采用线阵探测器。 通过Zemax软件对结果进行分析和评价, 表明仪器光学系统的尺寸为130 mm×125 mm×20 mm, 工作波段内光谱分辨率达到80 nm, 满足设计指标要求。 证明了该优化设计方法是可行的, 所得系统尺寸小、 性能高。

In order to miniaturize an infrared spectrometer, we analyze the current optical design of miniature spectrometers and propose a method for designing a miniature infrared gratings spectrometer based on planar waveguide. Common miniature spectrometer uses miniature optical elements to reduce the size of system, which also shrinks the effective aperture. So the performance of spectrometer has dropped. Miniaturization principle of planar waveguide spectrometer is different from the principle of common miniature spectrometer. In planar waveguide spectrometer, the propagation of light is limited in a thin planar waveguide, which looks like the whole optical system is squashed flat. In the direction parallel to the planar waveguide, the light through the slit is collimated, dispersed and focused. And a spectral image is formed in the detector plane. This propagation of light is similar to the light in common miniature spectrometer. In the direction perpendicular to the planar waveguide, light is multiple reflected by the upper and lower surfaces of the planar waveguide and propagates in the waveguide. So the size of corresponding optical element could be very small in the vertical direction, which can reduce the size of the optical system. And the performance of the spectrometer is still good. The design method of the planar waveguide spectrometer can be separated into two parts, Czerny-Turner structure design and planar waveguide structure design. First, by using aberration theory an aberration-corrected (spherical aberration, coma, focal curve) Czerny-Turner structure is obtained. The operation wavelength range and spectral resolution are also fixed. Then, by using geometrical optics theory a planar waveguide structure is designed for reducing the system size and correcting the astigmatism. The planar waveguide structure includes a planar waveguide and two cylindrical lenses. Finally, they are modeled together in optical design software and are optimized as a whole. An infrared planar waveguide spectrometer is designed using this method. The operation wavelength range is 8~12 μm, the numerical aperture is 0.22, and the linear array detector contains 64 elements. By using Zemax software, the design is optimized and analyzed. The results indicate that the size of the optical system is 130 mm×125 mm×20 mm and the spectral resolution of spectrometer is 80 nm, which satisfy the requirements of design index. Thus it is this method that can be used for designing a miniature spectrometer without movable parts and sizes in the range of several cubic centimeters.