Terahertz imaging system using high-Tc superconducting oscillation devices

Microwatt power oscillation devices at sub-terahertz frequency region between 0.3 and 1.0 terahertz(THz) were fabricated from high-Tc superconducting single crystalline Bi2Sr2CaCu2O8þd and used asa source of the transmission terahertz imaging system. As test examples, terahertz images of coinsand a razor blade placed inside the brownish paper envelopes with the spatial resolution of 1mm arepresented. The signal-to-noise ratio exceeds 130 in these images. Using a simple wedge-shapedinterferometer and analysing the interference fringe pattern, the wavelength of the terahertz wave iscalibrated within 0.1% accuracy. This interferometer also provides a simple method to measure theabsorption coefficient of the liquid sample. Two test measurements for distilled water and ethanol aredemonstrated and their absorption coefficients are obtained with 99.2% accuracy. This suggests thatour terahertz imaging system can be applied to many practical applications, such as biological andbiomedical imaging, environmental monitoring, microanalysis of impurities, structure and dynamicalanalyses of large molecules and ions in solution