This paper presents the principle of coherent population trapping (CPT) atomic clocks and describes a typical CPT clock system. Then the design of a light source system is designed and realized. This system uses thermal electrical cooler (TEC) to stabilize the temperature of the laser and uses direct digital synthesis (DDS) and lock-in amplifier techniques to stabilize the laser wavelength. Test results show that this system could control the wavelength in a range of 0.0012 nm using the temperature stabilizing principle; and under this condition the...