Abstract
In simple atomic systems, it is powerful and useful method on theoretical examination by laser spectroscopy. The simplest case, which is three-body-system, can be verified by 3He. We plan to measure the absolute frequency of the 21S-31D transition of 3He by two photon absorption and compare to the transition of 21S-23S and 23S-33D to decide the absolute frequency of 31D-33D. In this paper, we construct and Master Oscillator Power Amplifier (MOPA) laser system. The inject laser is an external cavity diode laser (ECDL) with 1009 nm of the wavelength and 42 mW of the optical power. Preliminary results of the MOPA laser system are as follows: maximum output power of 1.65 W, single frequency, threshold current of 1.898 A, slope efficiency of 0.405 W/A. We will improve the stability and use this laser as light source to measure the transition of 21S-31D by two-photon in the future.