| Summary: | 碩士 === 國立清華大學 === 物理系 === 100 === Setting up optical frequency standard and measuring absolute frequency can measure fundamental constants and test atomic and the quantum mechanical calculation atoms and molecules. In the past, building optical frequency standard relied on harmonic frequency chain which transfers the radio frequency standard to optical frequency regime. However, establishing a frequency chain is troublesome. Therefore, absolute frequency transition of atomic and molecular are measured to be secondary standard. Until the birth of optical frequency comb, the absolute frequency can be measured directly.
We used Ti:sapphire frequency comb for measuring the absolute frequency in the visible and near-infrared regime. We used an iodine-stabilized Nd:YAG laser near 532 nm for checking correctness of our optical frequency comb. The stability of our optical frequency is below 8.3×〖10〗^(-12) at 1 s average time.
In this thesis, we demonstrate two experiments. One is the absolute frequency measurement of the hyperfine splitting of the thallium atom. We scan the laser frequency near the thallium transition 6P_(1/2 )→7S_(1/2) and record its absolute frequency and absorption intensity. The other is absolute frequency measurement of N2O transition in mid-IR regime. We stabilize the laser frequency at the center frequency of the N2O transition and measure the laser frequency using our frequency comb. Also, we studied and build a common-path self-referencing interferometer. Unfortunately, we were unable to observe the signal of the offset frequency.
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