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光电导天线(PCA)产生太赫兹(THz)辐射受光生载流子输运情况的影响很大。考虑到GaAs材料光电导天线两能谷效应,修正了德鲁德-洛伦兹模型,得到了载流子输运情况并与经典扩散-漂移模型仿真结果进行了对比。同时采用了时域有限差分方法(FDTD)耦合载流子密度,仿真太赫兹辐射时域波形,并与太赫兹时域光谱系统(THz-TDS)测量时域波形对比。结果表明,两能谷效应修正的德鲁德-洛伦兹模型仿真辐射时域波形与THz-TDS测量波形吻合,14μm和34μm小孔径GaAs偶极子光电导天线在波长为800nm,脉冲半峰全宽为30fs,脉冲重复频率为75MHz,平均功率为327mW的钛宝石飞秒激光器照射条件下,GaAs材料衬底两能谷效应引起的载流子输运变化对THz辐射起关键作用。
Photoconductivity Antenna (PCA) Terahertz (THz) radiation is greatly affected by photogenerated carrier transport. Taking into account the two-energy valley effect of GaAs photoconductive antenna, the Druid-Lorentz model was modified and the carrier transport was obtained and compared with the simulation results of classical diffusion-drift model. At the same time, FDTD coupled carrier density was used to simulate the time-domain waveform of terahertz radiation and compared with the time-domain waveform of THz-TDS time-domain spectroscopy. The results show that the simulation waveforms of the Droid-Lorentz model with the two-energy valley effect coincide with the THz-TDS measurement waveforms. The 14μm and 34μm GaAs dipole photoconductive antennas with small aperture have good performance in the wavelength of 800nm, The change of carrier transport caused by the two-energy valley effect of GaAs material substrate plays a key role in the THz radiation under the irradiation of Ti: sapphire femtosecond laser with full-width of 30fs, pulse repetition frequency of 75MHz and average power of 327mW.