Photoconductive THz Sources Driven at 1550 nm

This chapter emphasizes Terahertz (THz) metrology–one of the most problematic and daunting topics in the THz field, especially the measurement of THz power. Through collaboration with the PTB in Berlin, Germany, it describes perhaps the most accurate THz power sensor in the world today, and demonstrates it an exemplary fashion. Optical-fiber coupling of THz PC devices is highly desirable for many reasons, including compactness of system integration, mechanical and thermal stability, and cost. 1550-nm operation is advantageous compared to 780 nm for reasons pertaining to optical-fiber technology. There are other issues too that are usually under-emphasized in THz device analyses. The three are ohmic contact effects, thermal effects, and circuit power limitations. The chapter addresses many pitfalls in THz power measurements, such as the leakage of 1550-nm drive laser power, and far-infrared thermal re-emission from the substrate on which the device is fabricated.