Spectral Measurements Based on Difference Frequency Modulation of Two PEMs Modulators
LI Shi-wei1,2, WANG Zhao-ba1,2, ZHANG Rui1,2，WANG Zhi-bin1,2,3
1. School of Information and Communication Engineering, North University of China, Taiyuan 030051, China
2. Engineering Technology Research Center of Shanxi Province for Opto-Electronic Information and Instrument, North University of China, Taiyuan 030051, China
3. School of Science, North University of China, Taiyuan 030051, China
Abstract：Due to the fact that the photoelastic modulator (PEM) interference signal frequency ranges from hundreds of megahertz to several gigahertz, and the array detector can not be applied to such high responded frequency, the application of PEM in spectral imaging is greatly limited . To solve this problems, a method is proposed in this paper to produce two PEMs of slightly different resonant frequencies with f1 and f2 which are applied to modulate the inputting optical signal. This method operates two PEMs of slightly different resonant frequencies f1 and f2 respectively，and the incident light can be modulated by the frequency difference of two PEM system. Thus, the interference signal contains low frequency modulation components contains the information of the incident light, and low frequency modulation component consists of a series of frequency-multiplier signals whose fundamental frequency is (f1-f2)/2. This low frequency modulation components can be detected with normal detector. After filtering the direct current component and high frequency signal, the incident light spectra can be obtained by the corresponding calculation. Since the difference frequency can be 2~3 orders of magnitude lower than the original resonant frequency of PEM, it can offer more time to array detector to process the inputting signal. What’s more, it does not require the same path difference and resonant frequency for the two PEMs, which can reduce the difficulty to PEM modulator design and control.
Key words：Spectral measurement; PEM; Difference frequency modulation; Imaging spectroscopy
基金资助: Key Program for International S&T Cooperation Projects of China (2013DFR10150) National Natural Science Foundation of China (61505180) and Young Science Foundation of Shanxi Province (2015021084)
作者简介: LI Shi-wei, (1980—), associate professor, School of Information and Communication Engineering, North University of China
e-mail:
lishiweili@126.com
引用本文:
李世伟，王召巴，张 瑞，王志斌. 一种基于两块PEM调制器的光谱测量方法[J]. 光谱学与光谱分析, 2017, 37(09): 2966-2973.
LI Shi-wei, WANG Zhao-ba, ZHANG Rui，WANG Zhi-bin. Spectral Measurements Based on Difference Frequency Modulation of Two PEMs Modulators. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2017, 37(09): 2966-2973.
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