High Sensitive Laser Spectroscopic Techniques and Their Applications to Precision Optical Frequency Control

Abstract: 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…
Key words: modulation transfer optical heterodyne spectroscopy; optical cavity enhancement; laser frequency-stabilization; ring optical resonant-cavity

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