Abstract
The national metrology institute of Germany, the Physikalisch-Technische Bundesanstalt (PTB), together with the company Sensor and Lasertechnik (SLT), develops pyroelectric detectors for radiation in the terahertz (THz) spectral range. The intention of this development is to deliver a highly sensitive, accurately calibrated detector for power measurement in the power range of time-domain spectroscopy (TDS) systems. This work reports about a large-area thin-film pyroelectric (TFP) detector applicable within a wide spectral range from 300 GHz to 30 THz and its radiometric characterization by PTB’s THz radiation sources. Applying coherent synchrotron radiation from the Metrology Light Source (MLS), laser radiation from a molecular gas laser and blackbody radiation from a water-heated blackbody to this detector reveal its potential to be capable of spanning an even wider THz frequency range than covered by TDS systems. To demonstrate this, its spectral responsivity was measured at different frequencies between 300 GHz and 30 THz by means of those three THz radiation sources.
Highlights
The terahertz and sub-terahertz frequency ranges down to approximately 100 GHz are the longest wavelength ranges where optical methods can still be used to measure the power of electromagnetic radiation
The power measurement in the extended THz range from 300 GHz up to 30 THz by optical methods needs a suitable detector with a well-known absorptance in this range
If the power of a radiation source with a broad spectrum within the THz frequency range shall be measured with this detector, the spectral responsivity of the detector has to be known for the complete frequency range of interest
Summary
The terahertz and sub-terahertz frequency ranges down to approximately 100 GHz are the longest wavelength ranges where optical methods can still be used to measure the power of electromagnetic radiation. This work represents a first step towards reliable and calibrated power measurement of TDS systems by introducing a recently developed new detector technology and showing its metrological potential by applying three different THz radiation sources available at PTB. One of these sources is the Metrology Light Source (MLS) [3], an advanced electron storage ring especially equipped to generate coherent synchrotron radiation in the sub-terahertz range around 300 GHz [4]. The detector was characterized for its spectral responsivity in the whole frequency range provided by the three sources from 300 GHz to 30 THz with the ultimate goal to demonstrate its flatness
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