CW-THz vector spectroscopy and imaging system based on 1.55-μm fiber-optics

We present a continuous-wave terahertz (THz) vector spectroscopy and imaging system based on a 1.5-mu m fiber optic unitraveling- carrier photodiode and InGaAs photo-conductive receiver. Using electro-optic (EO) phase modulators for THz phase control with shortened optical paths, the system achieves fast vector measurement with effective phase stabilization. Dynamic ranges of 100 dB.Hz and 75 degrees dB.Hz at 300 GHz and 1 THz, and phase stability of 1.5 per minute are obtained. With the simultaneous measurement of absorbance and relative permittivity, we demonstrate non-destructive analyses of pharmaceutical cocrystals inside tablets within a few minutes. (C) 2014 Optical Society of America