利用飞秒光频梳对激光波长进行高精度测量及实时跟踪的方法

Restricted by the frequency stability of the laser source and the detection method, the wavelength track accuracy is limited to 10-8, which limited the application of the metrology that based on the low noise laser. The combination of the automatic control and laser technology bring out the birth of the optical frequency comb. The 10-12 frequency stability of the optical frequency comb provides the possibility that the wavelength can be measured and tracked with higher accuracy. Therefore, this project proposes a new high-precision wavelength tracking method, which can improve the tracking accuracy by two magnitudes. In this project an interferometer will be built. Its signal source is an optical frequency comb. The wavelength of the optical signal causes the variation of the optical path difference, and, then, the variation will be detected by the Hansch-Couillaud detector, which outputs a voltage signal. The voltage signal will eventually be digitized by a high resolution analog to digital converter. The theoretical study will focus on the noise transfer function of the system in order to reduce the detection error and to improve the detection accuracy to the order of magnitude 10-9. The calibration experiment will be demonstrated when the system is built. The experimental results and Edlen empirical formula will be compared to verify the measurement accuracy further.

由于光源频率稳定度和测量方法的局限性，目前的激光波长跟踪精度无法优于10E-8，从而限制了激光度量精度的提升。自动控制和激光器技术的结合发展出了稳定度达到10E-12的飞秒光频梳，这为波长跟踪达到更高精度提供可能。本项目因此提出一种新的高精度波长测量及跟踪方法，有望将波长跟踪精度提高两个量级。计划以飞秒保偏光纤光频梳为探测光源，搭建双臂干涉仪。双臂干涉仪的光程差变化会反映空气中信号光波长的变化，这种变化会被Hansch-Couillaud探测器转化为电压信号。这个电压信号最终会通过搭建高分辨率的采样电路，以数字信号的形式输出测量结果。理论研究将围绕系统的噪声传递特性展开，进而在实验中采取相应的降噪手段，最终将探测精度提高到10E-9量级以上。系统搭建完成之后，将进行精度标定实验。测量结果和Edlen经验公式还会进行对比，以对标定精度提供佐证。

由于光源频率稳定度和测量方法的局限性，目前的激光波长跟踪精度无法优于10E-8，从而限制了激光度量精度的提升。自动控制和激光器技术的结合发展出了稳定度达到10E-12的飞秒光频梳，这为波长跟踪达到更高精度提供可能。为进行高精度波长跟踪，本项目对光纤飞秒激光器进行了放大及扩频改造，并且对其频率精度进行了测量。基于该光源，又搭建了双臂干涉仪和H-C探测器，调节了H-C探测器的输出范围。优化了整个探测系统的动态范围和采样精度。基于柔性铰链放大机构，发明了热释放法制作迷你型干涉仪，并得到了20urad的制作精度。我们进而将这种技术用于无镜架的Kerr Lens锁模激光器制作了。完成了业内首款全固化Kerr Lens飞秒激光器。该激光器可以在300 ~ 500 mA 的二极管泵浦电流下，获得15 mW的输出功率。在锁定其重复频率后，与传统构造的固体激光器的比较。其相位噪声降低了 50%。在其自由运行时，其频率稳定性提高了一倍。整个激光器的电功耗仅为5W，为Kerr lens锁模激光器在复杂环境下的应用提供了重要依据。