The aim of this project is to demonstrate a simple method of a multiple-frequency operation of passively Q- switched Nd: YAG optically pumped by an RF modulation Injection Laser Diode (ILD) at ( 808 nm wavelength, and controllable repletion rate (100 Hz – 4 KHz). A stable gain –switched pulse train of ( 1.064 nm ) wavelength is obtained with a maximum repletion rate of 4KHz and ( 17 ns ) pulse duration.