絕對頻率量測與共同路徑自參考干涉儀的研究

Absolute optical frequency measurement and the study of common-path self-referencing interferometer

陳仕恩(Shih-En Chen)

指導教授 ： 施宙聰

國立清華大學/理學院/物理學系/碩士(2012年)

https://doi.org/10.6843/NTHU.2012.00396

摘要

光頻標準的建立以及絕對光頻的測量，可用來測量物理常數、檢驗基本物理定律及原子分子量子力學的理論計算等。在過去，建立光頻標準需要經由頻率鏈(frequency chain)將射頻(radio frequency)頻段的頻率標準連結至光頻的範圍，以此作為標準。但是頻率鏈的建立非常繁雜，只有少數的原子及分子的躍遷頻率被測量，所以我們將這些原子及分子的躍遷頻率作為光頻標準。直到光頻梳的發明以後，使我們可以輕易地將射頻標準連結至光頻，量測光的絕對頻率。

實驗室中原有的鈦藍寶石(Ti：sapphire)光頻梳系統可以快速的量測可見光到近紅外光的絕對頻率。我們利用532 nm的碘穩頻Nd：YAG雷射校正光頻梳，確定光頻梳的量測值是正確的。此外，我們利用光頻梳量測碘分子穩頻雷射的穩定度，其一秒的Allan deviation優於 8.3×〖10〗^(-12)@ 。

我們利用光頻梳量測頻率，其一是鉈(thallium)原子6P_(1/2 )→7S_(1/2)躍遷頻率的量測；另一則是，N2O中紅外譜線的量測。前者，我們將雷射掃頻，同時量測吸收強度以及雷射頻率；後者，我們將雷射頻率鎖在躍遷譜線的中心，並使用光頻梳量測絕對頻率。另外，為了得到更穩定的光頻標準，我們建立一共路徑自參考干涉儀。不幸地，這一部分我們仍未看到干涉儀的訊號。

關鍵字

光頻梳 ； 碘穩頻 ； 干涉儀

並列摘要

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.

並列關鍵字

frequency comb ； laser stabilization ； interferometer

參考文獻

[4] A. Clairon, B. Dahmani, A. Filimon and J. Rutman, IEEE Trans. Instrum. Meas. 34, 265 (1985).

[10] M. Kourogi, K. Nakagawa and M. Ohtsu, IEEE J. Quantum Electron. 29, 2693 (1993).

[13] M. T. Asaki, C. P. Huang, D. Garvey, J. P. Zhou, H. C. Kapteyn and M. M. Murnane, Opt. Lett. 18, 977 (1993).

[21] P. Maddaloni, P. Cancio & P. De Natale, Meas. Sci. Technol. 20, 1 (2009).

[24] B. E. A. Saleh and M. C. Teich, “Fundamentals of Photonics,” 2nd Edition, Wiley Interscience (2007).