Abstract-Terahertz power calibration using absolute reference calorimeter

Hitoshi Iida, Moto Kinoshita, Kuniaki Amemiya, Yuya Tojima

https://onlinelibrary.wiley.com/doi/abs/10.1002/tee.22929?af=R

Here, we demonstrate an accurate terahertz (THz) power calibration toward tens of nanowatt levels at room temperature. A power reference standard based on a calorimeter with extremely low noise is realized by introducing vacuum insulation panels utilized for thermal insulation. The standard provides a measurement capability of 26.7 nW with the expanded uncertainty of 4.2% (k = 2) at 1 THz. The direct‐comparison calibration of a commercially available power meter is performed by considering its detectable power levels using the standard. A thermopile‐type power meter is used as the device under test, and its calibration factors are determined at 1 and 1.5 THz over a power‐level range of 0.66–1.56 µW. We evaluate the measurement uncertainties of the calibration and find a relative expanded uncertainty of 4.8–9.0% (k = 2).

 © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Abstract-Terahertz Pulse Reflection Imaging Using the Time-Domain Correlating Synthesis Method

Ryo Toh ;  Koji Suizu ;  Yuya Tojima

http://ieeexplore.ieee.org/document/7908987/

The synthetic aperture method is an attractive technique for terahertz nondestructive imaging without strict restraints on the beam form or the Rayleigh length of focus. However, the limitation of the aperture of the receiver array results in distortion and restricted lateral resolution of the reconstructed image. This paper introduces a nonlinear imaging processing principle, the correlating synthesis method, which has been applied in ultrasonic measurements. Using a pulse reflection mode terahertz time-domain spectrometry system and pulse compression preprocessing, we reconstructed images of metal cylinders. The results of comparisons with a synthetic aperture method verify the efficiency of the correlating synthesis method for improving the lateral resolution and eliminating fake images.