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浸入式光栅常应用于光学材料折射率较高的红外谱段.其特殊的工作模式会产生一系列普通反射式光栅不需面临的问题,而它们对于浸入式光栅的应用却十分重要.论文推导了普通光栅长波端与短波端谱线长度的关系.针对折射率与波长相关的特点,以短波红外(1.5~2.5μm)为例,分析其谱线位置分布及光谱分辨率变化特性.结果表明,浸入式光栅谱线分布相较于普通光栅有明显差异,“梯形”谱线会发生倾斜.在折射率变化较大的短波红外谱段,“梯形”谱线倾斜程度较明显.在以长波(2.5μm)配准Littrow条件时,谱线向短波端倾斜,以短波(1.5μm)配准时向长波端倾斜,且Littrow波长均漂离中心波长.由于折射率在热红外谱段变化较小,“梯形”谱线倾斜较小,更接近普通光栅情况.浸入式光栅的光谱分辨率随折射率变化而改变,同级中,波长增大分辨率增大;各级间,级数减小分辨率减小.同时,由于高级次(短波)分辨率大于低级次(长波),因此各级谱线长度之比不再满足普通光栅中的比例关系.
Immersed gratings are often used in the infrared spectrum with high refractive index of optical materials, and their special working mode will produce a series of problems that ordinary reflection gratings do not have to face, and they are very important for the application of immersion gratings. The relation between the length of the grating and the length of the short-wavelength end of the ordinary grating is analyzed.According to the characteristics of the refractive index and the wavelength, taking the shortwave infrared (1.5 ~ 2.5μm) as an example, the spectral distribution and spectral resolution of the grating are analyzed. , The spectral distribution of the immersed grating is obviously different from that of the ordinary grating, and the tilt of the “trapezoid” line will be tilted.When the “trapezoid” line tilts more obviously in the shortwave infrared spectrum with larger change of the refractive index . When Littrow conditions are registered with longwave (2.5μm), the line is tilted toward the shortwave end, tilted towards the longwave end at shortwave (1.5μm) registration, and the Littrow wavelength drifts away from the centerwavelength.Because the refractive index in the thermal infrared spectrum The change of the spectral resolution of immersion grating changes with the change of refractive index, and in the same level, the resolution of wavelength increase increases; the resolution of the “trapezoid” Between, reduce the number of levels to reduce resolution Since high order (short) is greater than the lower resolution views (long wave), and therefore no longer than the length of the line levels to satisfy the ratio between the grating normal.