Gentec-EO THZ-D User Manual

Page 20

Revision 1.1

THZ-D Series Instruction Manual

Pyroelectric THz probes cannot be considered as a reference detector for this portion of the Terahertz
spectrum, but can be used for relative measurements over the entire THz spectrum (30 THz to 0.1 THz).
The reference absorption curve of the new THZ12D-3S-VP was first validated through extensive
reflectance measurements together with multiple single wavelength power measurements using the INO
SIFIR-50 gas laser, calibrated Gold standards from PTB and additional validation from NIST power
measurements.

FIGURE 1: Reference Spectral Absorption Curves and Traceable Power measurements for Wavelength
Response Validation

In collaboration with the INO (National Institute of Optics) located in Quebec City, Canada, we have
characterized our THz detector absorbance at different wavelengths (from 3 μm to 430 μm) using FTIR
spectrometers that employ multiple sources to measure over this range. In between the different
wavelengths delivered by the source, sensitivities were interpolated from the FTIR absorption curve. The
absolute power of the source was measured with two different methods in order to increase the degree of
confidence in the measurement.
FTIR ab

sorption curves were validated in the 0.25 μm to 2.5 μm region with our in-house traceable

absorption measurement spectrometer.
In addition, traceable sensitivity measurements were made at 10.6 μm against a NIST gold standard and
at 118 μm against a PTB gold standard using our THZ12D-3S-VP and THZ9D-20mS-BL PTB traceable
detectors. These calibrated power measurements are shown on Figure 1 (Red and Blue dots).
As can be seen from the red curve in figure 1, we have successfully created a thermal THz detector that
meets our two criteria, for a low uncertainty reference, flat spectral response and high absorption. The
spectral response of the THZ12D is the same at 10.6 μm versus our NIST gold standard and at 119 μm
versus the PTB Gold standard measurement. Furt

hermore, the absorption variation from 10.6 μm to 600

μm is of the order of ± 4% and ± 2.5% from 119 μm to 600 μm. In addition, other points of validation were
made using NIST and INO measurements. A very good agreement has been obtained with the THZ12D-
3S-VP and THZ9D-20mS-BL PTB Gold detectors.