Abstract
Due to the coupling between longitudinal modes in the intracavity doubled diode-pumped solid-state(DPSS) laser, such as Nd doped YAG or YVO4, large amplitude fluctuations have been observed in the green output. This phenomenon knows as the “Green Problem”, and it seriously restricts the development and applications of intracavity doubled DPSS laser. A lot of researchers put forward different solutions to the green problem. However, they mostly focused on designing a complicated structure of the resonance cavity. In this thesis, we illustrate the green problem based on previous works, mostly done by Baer[2] and James[7], and obtained the green noise simulation from the rate-equations. In addition, we discuss the parameters which affect the behavior of green noise. In the experiment, we used an 808nm laser diode to pump a Nd:YVO4/KTP crystal pair. The green noise was observed by photodiode. To eliminate the green noise, we designed an electronic circuit to modulate the laser diode. The number of the longitudinal mode by the Fabry-Perot interferometers was also measured. The results show that the green noise was suppressed and the laser operated in single mode at high modulation frequency.