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可调谐式二极管激光器由于其体积小、固体介质的可靠性与稳定性、以及价格低廉等特点 ,在光谱学和环境学中得到了广泛应用。Harvey -Myatt外腔式设计是在所有Fabry -Perot二极管激光器中实现无跳模、窄线宽的最佳方案之一。利用这种外腔式二极管激光的新型分析技术—低频波长调制和谐波探测法 ,我们利用对外腔式二极管激光通过施加低频交流电压控制其反馈镜的压电陶瓷 ,实现输出光连续调谐的低频波长调制的方法 ,对Cs原子D2 线 (未饱和 )进行了测量 ,获得了高次谐波探测方式下的高灵敏度以及高分辩率的吸光光谱。这种低频 (数KHz)电压调制的方法较常见的高频波长调制的优点是不需要快速的光电探测器 ;同时 ,利用锁相放大器 (如SR830 )很容易获得信号的高次谐波。另外调制压电电压较常见的电流调制引起的输出光能量起伏小 1- 2个数量级 ,背景噪声较小 ,探测灵敏度得到了进一步提高。实验结果表明调制压电电压引起的输出光能量起伏较小 ,二次谐波 ( 2f)探测的信噪比有较大的改善 ,而高次谐波探测较常见的 2f探测方法具有更高的分辩率和信噪比
Tunable diode laser has been widely used in spectroscopy and environment due to its small size, reliability and stability of solid medium, and low cost. The Harvey-Myatt external cavity design is one of the best ways to achieve modeless, narrow linewidth in all Fabry-Perot diode lasers. Using this new analysis technique of extracavity diode laser - low-frequency wavelength modulation and harmonic detection, we use a piezoelectric ceramic that uses an external-cavity diode laser to control its feedback mirror by applying a low-frequency AC voltage to achieve continuous low-frequency Wavelength modulation method, the Cs atom D2 line (not saturated) was measured to obtain high-harmonic detection mode of high sensitivity and high-resolution absorption spectra. The advantage of this low frequency (KHz) voltage modulation method over the more common high frequency wavelength modulation is that it does not require a fast photodetector; at the same time, higher harmonics of the signal are easily obtained with a lock-in amplifier such as the SR830. In addition, the voltage fluctuation of the output light caused by the modulation voltage is lower by 1-2 orders of magnitude than the common current modulation, the background noise is smaller, and the detection sensitivity is further improved. The experimental results show that the voltage fluctuation of the output light caused by the modulated piezoelectric voltage is small, the signal-to-noise ratio of the second harmonic (2f) detection is greatly improved, and the higher harmonic detection has a higher Resolution and signal to noise ratio