In this chapter, the theoretical modeling, numerical simulation and experimental study of PCA are thoroughly discussed. The principles of three representative models, namely, Drude-Lorentz model, equivalent circuit model and full-wave model, were introduced. After summarizing the pros and cons of each model, the full-wave model was chosen for numerical simulation of PCA, as it has least physical assumptions and thus should be the most accurate. The numerical simulation was carried out using in-house codes on the MATLAB^® platform, which was also verified using commercial software. The radiation properties of a PCA were then thoroughly studied by varying several important parameters, such as laser power, bias voltage, photoconductor material properties and laser pulse width. To demonstrate the application of this model, two new PCAs were designed and simulated, and enhanced THz radiations were predicted for both. The influences of the photoconductive material, antenna structures, etc. on the THz radiation power and bandwidth are systematically investigated to gain a more comprehensive understanding of a PCA. The general radiation mechanism of the PCAs is further studied by implementing the polarization effect and cancellation effect measurements. Recent progresses of the PCA structure development using nanostructure and plasmonic antenna electrodes to improve the THz radiation power/efficiency are briefly reviewed. In addition, the THz near-field spectroscopic technique based on PCAs is proposed to overcome the resolution limit and achieve sub-wavelength resolution. Specifically, incorporating the Hadamard multiplexing method with an emitter array for the THz near-field configuration, the system SNR is enhanced, agreeing well with theoretical prediction. With more array elements, the system SNR can be further improved. Various THz applications are explored utilizing the far-field and near-field THz-TDS setup, including material characterization, imaging and sensing. With the advancement of THz far-field and near-field systems incorporating PCAs in recent years, more innovative and practical THz applications will be enabled.

Chapter Contents:

• 3.1 Introduction of THz technology and photoconductive antenna
• 3.1.1 Importance of THz technology
• 3.1.2 THz generation
• 3.1.3 Pulsed THz generation
• 3.1.4 Photoconductive antenna
• 3.1.5 Terahertz time-domain spectroscopy
• 3.2 Theoretical modeling and numerical simulation
• 3.2.1 Motivation and challenge
• 3.2.2 Drude–Lorentz model
• 3.2.3 Equivalent circuit model
• 3.2.4 Full-wave model
• 3.2.5 Simulation examples of full-wave model
• 3.2.5.1 Validation of the model
• 3.2.5.2 Parametric studies of the PCA by simulation
• 3.2.5.3 Design of new PCAs with enhanced THz radiation
• 3.3 Experimental characterization of PCA component and system
• 3.3.1 Far-field THz-TDS
• 3.3.1.1 Introduction and motivation
• 3.3.1.2 Far-field THz-TDS system setup
• 3.3.1.3 Experimental characterization of PCA
• 3.3.1.4 Polarization effect and cancellation effect
• 3.3.1.5 THz radiation power/efficiency improvement
• 3.3.1.6 Applications of the THz-TDS system
• 3.3.2 THz near-field microscopy
• 3.3.2.1 Motivation
• 3.3.2.2 THz near-field system setup
• 3.3.2.3 System performance characterization
• 3.3.2.4 Applications of THz near-field system
• 3.4 Summary
• References

Inspec keywords: metamaterial antennas; submillimetre wave antennas; terahertz wave devices; photoconducting devices; millimetre wave antennas; nanophotonics

Other keywords: numerical simulation; bias voltage; laser power; photoconductor material properties; nanostructure antenna electrodes; laser pulse width; radiation mechanism; Hadamard multiplexing method; bandwidth; near-field; material characterization; far-field; experimental study; THz near-field spectroscopic technique; full-wave model; THz photoconductive antennas; photoconductive material; equivalent circuit model; antenna structures; radiation properties; plasmonic antenna electrodes; Drude-Lorentz model

Subjects: Single antennas; Nanophotonic devices and technology