(An) analysis of the thin film by using THz-TDS and a spectral analysis and design of an integrated photomixer/antenna

Abstract

The terahertz (THz) waves are categorized as two distinct types: the pulsed-wave (PW) having wide frequency bandwidth from a few tens of GHz up to over one THz; the continuous-wave (CW) having narrow frequency bandwidth. In this dissertation, two major topics are investigated. One is the analysis of the ferroelectric thin film by using THz time-domain spectroscopy (THz-TDS) that is the application of the THz PW. The other one is the spectral analysis and the design of an integrated photomixer/antenna in the all-optoelectronic THz photomixing system, which is the application of the THz CW. An integrated photomixer/antenna generates the THz CW through the photomixing on the ultrafast photoconductor by the two distributed feedback lasers (DFB-LDs) having slightly different wavelengths. The THz-TDS is a powerful technique that can extract the both real and imaginary parts of the complex dielectric property of materials by measuring the THz electromagnetic pulses transmitting the materials in time domain. In modern electronics, the thin dielectric or semiconductor layers are frequently used and the frequency of the electronics is rapidly increasing. And the nanostructured materials having a high potential is fabricated in thin film state for photonics and nanodevices. Therefore, it is very important to investigate the thin layered systems in THz frequency range. Moreover, the emerging THz investigation of biomolecules is compelled to thin layers due to the small material quantities typically available. In this dissertation, the ferroelectric thin film is analyzed to establish the method for the analysis of the thin film by using THz-TDS. The multiple reflections of THz pulses within the thin film can’t be temporally separated and they get superimposed. Thus, the multiple reflections within the thin film are carefully considered to analyze the thin film by using THz-TDS. And the error function between calculated and measured data is introduced to extract the complex ...