Design And Development Of A 399nm Laser System For Yb Optical Lattice Clocks

In the past decades, optical atomic clocks have received accelerated development and become the new focus in the field of time and frequency standards because their theoretical prediction of fractional frequency uncertainty can reach a level of 10-18 and they have a great potential to be the time and frequency standards of next generation instead of cesium fountain clocks which have an fractional frequency uncertainty of 5x10-16. Therefore, optical atomic clocks attract intense attention from scientists all over the world. Ytterbium is a strong candidate for optical atomic clocks since its natural linewidth of clock transition only has few mHz. One of key processes to realize Yb optical atomic clocks is to slow down ytterbium atoms by first cooling and Zeeman slow using the 1S0-1P1 transition whose transition wavelength is 399nm. Consequently, a compact and stable 399nm laser source is essential for ytterbium optical clocks.We utilized the method of second harmonic generation of 798nm diode laser in an external enhancement resonator with LBO crystal and presented theoretical and experimental analysis of every factors that affect frequency doubling efficiency. This thesis mainly consists of the following parts:(1) We give a brief overview of second harmonic generation, analyze the procedure of frequency doubling in an external cavity with LBO crystal theoretically and calculate the phase matching angle of LBO crystal, Boyd-Kleinmen focusing factor, optimum focusing condition and single pass conversion efficiency.(2) We design an external ring cavity according to cavity stability condition (|A+D|<2) and optimum focusing condition. The optimum processes of the cavity based on three parts, including astigmatism compensation, mode matching and impedance matching.(3) We introduce the scheme of frequency stabilization by polarization spectroscopy of a reflecting reference cavity and implement it to frequency lock the external ring cavity to the 798nm diode laser source. All the feedback stabilization electronics including photo detector, signal analyzer, PID, high-voltage amplifier are made personally.(4) We present a brief analysis of 399nm laser, including factors related to external ring cavity, optimum LBO crystal temperature and the output 399nm laser power and frequency doubling efficiency.