摘要
本论文从理论和实验两方面，对两种高灵敏高分辨光谱技术——激光调制转移光外差光谱技术和环形腔增强调制转移光外差光谱技术——进行了一系列分析和比较，并对其在光频精密控制研究领域的应用特性作了重点研究。
理论上，从光学谐振腔内电场叠加的原理出发，进一步论证了环形光学谱振腔内光场分布及吸收增强原理，并将环形腔增强技术应用于调制转移光谱技术，推导出四波混频信号的增强因子；并提出了旨在优化腔增强调制转移光谱技术的腔体设计，为获得高稳定度和高复现性的光频标研究提供其有最佳鉴频特性的高信噪比光谱信号。另外，还从理论上估算了调制转移光潜稳频技术可能达到的频率稳定度，为实验提供了理论依据。
实验上，以半导体泵浦的固体激光器为光源，采用调制转移光外差光谱技术获得碘分子在532nm波段附近的超精细结构谱，并把激光频率锁定在R(56)32-a10这条超精细跃迁谱线上，实现了激光频率的绝对锁定。此外，改进了环形腔增强调制转移光谱技术，获得了碘分子在532nm波段附近的超精细结构谱，与不加腔的调制转移光谱信号相比光谱信噪比有显著增加，有望实现精度更高的激光频率锁定。
In this work, we have made comprehensive comparison between two sorts of high-sensitivity and high-resolution spectroscopic techniques: modulation-transfer optical heterodyne spectroscopy and ring cavity enhanced modulation-transfer optical heterodyne spectroscopy by theoretical analysis and experimental tests. And also we mainly introduced their applications to the precision optical frequency control.
The theoretical analysis began with the superposition principle of the electrical field in optical resonant cavities based on which we have demonstrated the mechanism of the enhancement effect of the ring cavity. In the research of the modulation transfer spectroscopy, we have borrowed some idea from the technique of cavity enhancement, and obtained the enhancement factor for four-wave mixture signal. We have also intensively studied how to optimize the design of a practical cavity-enhanced modulation-transfer spectrometer that would be able to give first-rank spectroscopic signal measurement for the application of high-stable and high-reproducibility optical frequency standard. Lastly, we estimated the upper limit of the frequency stability using modulation-transfer spectroscopy, which could be used as a reference for experimental application.
In our experimental work, we have measured the hypeiline spectra of I2 at the 532 nm region taking advantage of the traditional modulation transfer spectroscopy, using a diode laser pumped solid state laser as the light source The absolute frequency lock was realized by stabilizing the optical frequency of the laser to the R(56)32-a10 hypeifine structure of I2. In addition, we have improved the technique of ring-cavity enhanced modulation-transfer spectroscopy, using which we also obtained the hyperfme spectra of I2 at the 532 nm region. Compared to the modulation transfer spectrum without cavity, (he signal to noise ratio (S/N) is obviously improved, showing that this technique will hopefully lead to higher precision optical frequency-stabilized.
引文
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