چكيده به لاتين
The Terahertz gap located between the microwave and infrared region of the electromagnetic spectrum and has wide applications in various fields such as medical, security, spectroscopy and astronomical studies. Nowadays, among the different methods of producing terahertz, photoconductive antenna is considered more than the other methods because it is low cost, has compact design and can generate broadband radiation. But one of the most disadvantages of this method is its low efficiency.The purpose of this Research is to study the mechanism of photoconductive antennas and simulation of Terahertz pulse antennas. Also effective ways to increase the efficiency of these types of antennas has been suggested. According to the equations of semiconductors the pulse current generated in the antenna gap is obtained by the Drude-Lorentz theory and from this photocurrent, the electric field of Terahertz radiation can be calculated.
In this thesis, three circuit modeling has been used to study photoconductive antennas. The third modeling is more complete, because it has more circuit elements therefore this model contains more physical phenomena that occur in the antenna and its results are closer to the experimental measurements.
The temperature of the antenna, for a variety of reasons, increases during the process of generating terahertz radiations, the effect of temperature on the performance of the antenna is studied. Also frequency-dependent antennas could be considered by transferring the equations from the time domain to the frequency domain.. At the end of this thesis, the third circuit modeling is utilized for temperature and frequency dependent antennas.
In the first chapter of this thesis, we give a brief history of terahertz science and introduce this region of the electromagnetic spectrum and then its properties and applications are introduced. This chapter also gives a brief description of the method of producing terahertz through plasma. In the second chapter, the structure of the photoconductive antenna and its related equations are studied. In the following chapter, we investigate three circuit modeling of photoconductive antenna with gallium arsenide semiconductor. In the fourth chapter, the effect of temperature and frequency parameters on these antennas is studied
Finally, in chapter five different methods; have been suggested for increasing the efficiency of the Terahertz antennas based on the gallium Arsenide semiconductor
