Research On Electro-optically Q-switched Laser With A High Repetition Rate

Recently high repetition rate and short pulse width lasers play an increasingly important role in the fields of laser communications, laser radar, laser measurement, laser medical and laser micro-processing and so on, as these fields attracted more and more attention. The electro-optically (EO) Q-switch has caused great concern because it has an excellent switch ability, rapid response speed(nanosecond or even the subnanosecongd degree) and can produce short pulse width easily. It has been reported that Keming Du et al in Germany has achieved a laser output which the repetition rate is from 10 to 50 KHz, and the narrowest pulse width is 6.45ns. In the domestic, Xiaoli Li et al had achieved a repetition rate of 25 KHz and the pulse width is 9.5ns.This paper has made a detail characteristic analysis of the BBO crystal. It was calculated that the voltage ofλ/4 in this paper is 3.26KV. Using the analysis software, it is known that, the temperature distribution in the profile of the crystal is symmetrical, but it is not so for the stress distribution for there has tow fixtures in four of tow sides of the crystal. It is that caused a different thermal focal length between the X direction and the Y direction. It is calculated that the thermal lens is a minus lens with a long focal length, and the loss of depolarizer is so small that it can be neglected when the power of the oscillating beam is low. Using the rate equation to analysis the inherent relations among the output power, the repetition rate and the pulse width. It is reported that the ratio of Ni/Nt is an important factor to the output parameter. Then an analysis of the properties of the resonant cavity is made. Finally, it is given that at the repetition rate of 10 KHz, the pulse width of the output laser is 3.8 ns.