Influence Of Space-charge Field In Photoconductor To Photoconductive Semiconductor Switches And THz Photoconductor Antenna

As an wave-band in the electromagnetic spectrum which hardly being used to this day, terahertz has came to be a focus to scientists of all over the would. Because of it's unique character, THz may give prominent influence to the field of imaging, biology, communication, national-defense and so on. Being a source of microwave it is provided with merit of power and bandwidth at the same time, photoconductive semiconductor switches has unique predominance in the field of power pulse technology and THz sources. Carries created by ultra-fast laser pulse accelerate in the field of the photoconductor and form a transient photocurrent. The shape of the photocurrent lies on the movement of the carriers, as well as the movement of the carrier's lies on the field in the photoconductor. The field in large-aperture photoconductors is mainly composed of bias field, space-charge field formed by transient distributing of carriers. Bias field is comparatively static, so the influence to carriers is static too. Oppositely, space-charge field changes along with the movement of the carriers, and influences the movement of carriers synchronously. It's an intricate process and can not to be ignored in PCSS's. In the case of triggering by high power optical, space-charge field can intensity influence the movement of the carrier. Thus, space-charge field in excitated photoconductor can intensity influence not only the shape of photo-electric current of PCSS's, but also the terahertz out put of photoconducting antenna. In this paper, the forming and movement of space-charge field are simulated by means of FDTD method. And the result of simulate indicates that several charge domains could exist in photoconductor at the same time.In this paper, through analyzing of the result of simulation, the working model of PCSS's was particular classed based on the movement of the carriers. By simulating of transient field in the photoconductor of THz photoconductive antenna, the curve of instant electric current was given here, and the result was validated by FDTD method. The influence of transient field to THz out put was mentioned in this paper too.THz radiation generated from a Si3N4 covered GaAs photoconductive dipole antenna is investigated in the paper. Comparing with uncovered antennas with the same gap size, the covered antenna has higher breakdown voltage at the same optical exciting power, and it's THz out put is 1.5 times of uncovered antenna.