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Continuous wave terahertz wave spectrometer based on diode laser pumping: potential applications in high resolution
Tadao Tanabe1, Srinivasa Ragam, Yutaka Oyama
1Department of Materials Science, Graduate School of Engineering, Tohoku University, Aoba-yama 6-6-11-1021, Sendai 980-8597, Japan. tanabet@material.tohoku.ac.jp
The Review of Scientific Instruments
|December 2, 2009
Summary
We developed a high-resolution terahertz (THz) spectroscopy system using a continuous wave (cw) THz generator. This advanced system offers a wide tuning range and precise measurements for various applications.
Area of Science:
- Physics
- Spectroscopy
- Materials Science
Background:
- Terahertz (THz) spectroscopy is a powerful tool for material analysis.
- Developing high-resolution THz systems with wide tuning ranges remains a challenge.
- Continuous wave (cw) THz generation offers advantages for spectroscopic applications.
Purpose of the Study:
- To construct a high-resolution THz spectroscopic system with automatic scanning control.
- To demonstrate the system's capability for measuring transmission characteristics and absorption spectra.
- To highlight the system's potential for high-resolution spectroscopic applications.
Main Methods:
- Utilized a continuous wave (cw) THz wave generator based on difference frequency generation.
- Employed phonon-polariton mode excitation in Gallium Phosphide (GaP).
- Integrated tunable external cavity lasers and distributed feedback (DFB) lasers for pump and signal sources, with automated frequency tuning via DFB laser temperature control.
Main Results:
- Successfully constructed a high-resolution THz spectroscopic system with automatic scanning.
- Demonstrated THz wave transmission characteristics of water vapor.
- Obtained the absorption spectrum of polyethylene in the 1.97-2.45 THz range.
- Achieved spectroscopic measurements at an output power of 2 nW using a 15-mm GaP crystal at 2 THz.
Conclusions:
- The developed cw THz spectrometer exhibits a wide frequency tuning range (0.7-4.42 THz).
- The system demonstrates a high resolution with an estimated linewidth (full width at quarter maximum) <8 MHz.
- This system holds significant potential for various high-resolution spectroscopy applications.
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