為了執行從亞穩態到nD態的原子氦光譜，需要用波長為535至552 nm的激光源激發氦原子池。 因此，此類項目的基本初始步驟是開發激光源。 考慮之後，將由半導體激光二極管泵浦的外腔激光器組裝成Litrow構造。 外部腔二極管激光器用於發射約1070 nm的紅外光束，然後通過倍頻工藝與大量的非線性晶體轉換為535 nm的綠光束。 在我們的實驗中使用了摻Mg的全鈮酸鋰晶體。 第一步，通過執行原子碘的吸收光譜測試綠色激光器

In order to perform the spectrum of atomic Helium from a metastable state to nD states, the Helium atom cell is required to be excited by the laser source with the wavelength from 535 to 552 nm. Therefore, the foundationally initial step for this kind of project is developing a laser source. After consideration, an external cavity laser pumped by a semiconductor laser diode was assembled in Litrow configuration. The External Cavity Diode Laser is used to emit an infrared beam, at around 1070 nm, which then is converted into a green beam, at 535 nm, by the frequency-doubled process with a bulk of the nonlinear crystal. The Mg-doped congruent Lithium Niobate crystal was used in our experiment. As the first step, the green laser is tested by performing the absorption spectrum of the atomic iodine.

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