Development of visible/near-infrared multiband laser filter film
doi: 10.37188/CO.EN-2025-0031
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摘要:
滤光片作为光电探测系统中的关键部件,能够简化光学系统并提高探测效率。根据使用需求,需要设计并制备出一种多达5个波段的可见/近红外滤光膜,同时满足2个波段高反射和3个波段高透过的要求。因此,本文对膜系设计、薄膜制备工艺以及膜层厚度的控制精度进行了系统研究。在本工作中,将短波通膜系与长波通膜系进行叠加,并调整膜系的周期数和匹配系数,以满足截止波段的要求。此外,运用Smith方法对带通膜系进行优化透过波段,从而完成可见/近红外多波段激光滤光膜的设计。在制备过程中,结合膜层的灵敏度,通过反演分析对各光学监控片所监控的膜层。对监控过程中光信号较弱的光学监控方案进行模拟和修正,并匹配光信号较强的监控波长,进而提高了膜层厚度的控制精度以及在指定波长范围内的透过率。最终,制备的滤光膜实际物理厚度为9.66微米,与理论设计厚度的误差小于0.4%,且3个透过波段的透过率均超过99%。在455~500 nm和910~
1000 nm波段的平均透过率分别为0.45%和0.16%。Abstract:Filters, as a key component in the photoelectric detection system, can simplify the optical system and improve detection efficiency. Based on the usage requirements, a visible/near-infrared filter film with up to 5 wavebands needs to be designed and prepared, while simultaneously satisfying high reflection in 2 wavebands and high transmittance in 3 wavebands. Therefore, we have conducted a systematic study on the film design, thin film preparation process, and control accuracy of film layer thickness. In this work, the short-wave pass film system is superimposed with the long-wave pass film system, and the number of cycles and matching coefficient of the film system are tuned to meet the requirements of cut-off band. Additionally, Smith method was used to match bandpass film system to optimize the transmission band and complete the visible/near infrared multiband laser filter film design. In the preparation process, combined with the sensitivity of the film layer, inverse analysis is used to invert the film layer monitored by each optical monitoring chip. The optical control scheme with weak optical signal in the monitoring process is simulated and corrected, and the monitoring wavelength with stronger optical signal is matched, resulting in an improvement of the control accuracy for the film thickness and the transmittance in the specified wavelength range. Ultimately, the actual physical thickness is 9.66 μm, and the error with the theoretical design thickness is less than 0.4%, and the transmittance of the specified 3 wavebands exceeds 99%. The average transmittance of the cut-off bands at the 455−500 nm and 910−
1000 nm is 0.45% and 0.16%, respectively.-
Key words:
- optical film /
- multiband /
- film system design /
- reverse analysis
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Figure 1. Transmittance spectral curves of (a) long-wavelength-passing and (b) short-wavelength-passing with different period numbers, (c) superimposed transmittance spectral curves of film system at period number S1=8, S2=15, (d) initial design and (e) optimized design transmittance spectral curve, (f) transmittance spectral curve of antireflection film.
Table 1. Technical parameters of multiband laser filter film.
Parameter Specification Angle /° 0 Transmission band /nm 880 & 1064 &1083 &1342 Transmittance /% ≥99 Waveband of cut−off region /nm 455-500 & 910- 1000 Transmittance of cut−off region /% <1 Table 2. Equipment process parameters.
Material Substrate
Temperature/◦CDegree of
Vacuum/mbarDeposition
Rate/nm·s−1Flow Rate of
O2/sccmAPS HPE Ta2O5 180 5×10−5 0.3 15 35 SiO2 0.7 25 25 Table 3. Spectral theoretical values and period numbers.
Cycles number of S1 T455-500nm /% Cycles number of S2 T910-1000nm /% 2 43.23 3 44.66 4 10.68 6 12.49 6 2.42 9 5.70 8 0.56 12 0.87 10 0.13 15 0.12 12 0.02 18 0.07 -
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