Precise phase measurement of continuous terahertz-wave based on balanced self-heterodyne technique and its application to phase-contrast imaging

We demonstrate that the photonics-based self-heterodyne system enables us to measure the phase change of the continuous THz-wave with the theoretical uncertainties limited by the signal-to-noise ratio (SNR) of the amplitude measurement. When the SNR was 44 dB, the standard deviation of the phase measurement was 0.37 degree, which is 10 times better than the previous method. We apply this system to phase-contrast imaging to show that it is effective for imaging of materials exhibiting a small absorption in the THz range.