荧光干扰是拉曼光谱检测过程中常见的干扰因素之一, 而移频激发法是一种有效的克服荧光干扰的检测手段。 移频激发法利用两个波长相近的激光分别激发被测物质, 并将获得的拉曼光谱进行差谱。 由于两次激发的荧光背景相同, 而拉曼特征峰会产生平移, 因此可有效地消除荧光背景的干扰, 进而利用一定的算法还原拉曼特征峰。 移频激发法的关键在于两个激发光波长的稳定性, 不稳定的波长差将严重影响对拉曼特征峰的还原效果。 本文研制了一种拉曼光谱测试系统, 该系统的双波长LD模块能够产生两个波长稳定的激发光(分别为784.7和785.8 nm), 满足移频激发法的测试要求。 影响激发光波长稳定性的因素主要是光功率和温度, 本系统中对这两个因素均进行了实时的监控, 以保证激发光波长的稳定。 系统的硬件部分主要包括ARM主控板、 双波长LD模块及其驱动电路、 温度控制板、 数字光开关、 光谱检测光路和光纤探头(两个高功率的蝶形封装激光器); 软件部分可自动获取被测物质的拉曼光谱图, 并对其进行后续的处理。 在稳定性测试实验中, 对系统驱动电源电流和激光器温度的稳定性均进行了测试。 测试结果显示, 电流波动范围小于0.01 mA、 温度变化范围小于0.004 ℃, 能够有效地保证激发光波长的稳定性。 最后, 对某品牌花生油进行了拉曼光谱检测, 并对检测结果进行了处理, 获得了良好的效果。

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 ℃. 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.