研究目的
To achieve a highly sensitive measurement of absolute terahertz power at nanowatt levels at room temperature.
研究成果
A highly sensitive absolute THz power measurement was demonstrated at tens of nanowatt levels using a THz calorimeter operating at room temperature. Very stable measurements were realized by introducing an extremely low noise amplifier and multilayered vacuum thermal insulation jackets. The source of uncertainty for the measurement was also analyzed. As a result, an accurate power measurement of 26.7 nW with a relative expanded uncertainty of 4.2% (k = 2) at 1 THz at room temperature was achieved.
研究不足
The study focuses on measurements at room temperature and at a specific frequency (1 THz). The sensitivity and accuracy might vary under different conditions.
1：Experimental Design and Method Selection:
A highly sensitive calorimetric measurement system was constructed using an extremely low noise amplifier and multilayer thermal insulation jackets. A vacuum insulator was used to mitigate thermal disturbance.
2：Sample Selection and Data Sources:
The THz wave was generated by a photomixer driven by two distributed feedback lasers having different wavelengths of the
3：5 μm band. The frequency generated was 1 THz. List of Experimental Equipment and Materials:
The system included a mechanical shutter, an attenuator, low-pass filters, and vacuum insulation panels.
4：Experimental Procedures and Operational Workflow:
The THz wave was controlled by a mechanical shutter, and its intensity was attenuated to tens of nanowatt levels. The effect of thermal disturbance was suppressed by covering the calorimeter with multilayered thermal insulators using vacuum insulation panels.
5：Data Analysis Methods:
The THz power was determined by measuring the change in the DC heater power under a balanced state.
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Bi-Te thermo module
Detects temperature increase and converts it to a DC signal.
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ultra-low noise amplifier
Amplifies the DC signal from the thermo module.
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vacuum insulation panels
Used to cover the calorimeter to suppress thermal disturbance.
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photomixer
Generates the THz wave driven by two distributed feedback lasers.
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distributed feedback lasers
Drives the photomixer to generate the THz wave.
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mechanical shutter
Controls the THz wave shining into the calorimeter.
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attenuator
Attenuates the intensity of the THz wave to tens of nanowatt levels.
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low-pass filters
Rejects infrared leakage from the photomixer.
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optically polished neutral density filter glass
NG1
Schott
Used in the calorimeter as an absorber.
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