[Raman Spectroscopy Measurement System of Dual Wavelength Laser Module].

ABSTRACT

Fluorescence interference is one of common interference factors during detection of Raman spectroscopy, while shifted-excitation Raman difference spectroscopy (SERDS) is an effective detection means to reject it. SERDS excites the test substance by two laser with different wavelengths, then difference the obtained Raman spectroscopies. SERDS can eliminate the fluorescence interference effectively, because the fluorescence backgrounds of the two spectroscopies are the same while the Raman peaks are translated. The key factor of SERDS is the stability of the two excitation light wavelengths, the instability of wavelength difference would seriously affect the characteristics of the Raman peak reproduction. In this paper, the Raman spectroscopy measurement system is presented, where dual wavelength laser module can stably produce two bunch of excitation light (respectively 784.7 and 785.8 nm), which satisfies the requirements of SERDS detection. The major factors influencing wavelength of the laser are laser power and temperature. The system monitors them in real time to guarantee the stability of exciting light's wavelength. The hardware framework of this measurement system is mainly composed of ARM, dual wavelength laser module as well as its driving circuit, temperature control circuit, a digital optical switch, a spectrometer; the software of this system can achieve the Raman spectrogram automatically and then carry on the subsequent processing. The stability tests of this system for drive current and laser temperature are done. The experimental results demonstrate that the range of current proves to be less than 0.01 mA, the range of temperature less than 0.004 degrees C. The system can guarantee the stability of excitation wavelength effectively. Finally, perform the Raman spectroscopy detection to sesame oil of some brand and get good results.