Research On Electro-Optic Modulation System With High-power At High-speed And Its Application In Terahertz System

In the field of the terahertz wave optical modulation technology, the minority carrier lifetime of materials limits the modulation performance of the system, as the result, high-speed and high-power electro-optic modulation systems are in demand. Based on the field, a high-speed and high-power electro-optic modulation system is developed and applied to promote the modulation performance of the system.Firstly, based on the electro-optic effect, a precise and reliable light path of high-speed and high-power electro-optic modulation system is designed and set up. The wavelength of system output laser is 808 nm, and the bandwidth of it is 100 MHz in theory. The maximum of output power is 4 W/mm2 and the maximum of extinction ratio is 80%. Secondly, the drive technology of electro-optic crystal is further studied, then both the amplification circuit and switch circuit are researched. A high-voltage and high-frequence driver which is suitable for capacitive load is developed and applied to the electro-optic modulation system improving the dynamic characteristics. Both the resistive and capacitive load can be driven and the capacitive load's capacity can be driven is hundreds of pF. Both the amplitude and duty cycle of the output pulse can be changed. Its maximum of peak-to-peak value is 300 V. Its repetition frequency is up to 10 MHz and its rising edge is less than 20 ns. Its main technical indicators have reached advanced level and it has great market value. Finally, a scheme of terahertz optical modulation is introduced which based on the photoconductive effect of high resistance silicon. The terahertz optical modulation system is built with the electro-optic modulation system which enhancing the modulation performance. Through the experimental test and analysis, the modulation depth of the system is 50% and the modulation speed can exceed 6.8 MHz theoretically.