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Widely tunable quantum cascade laser-based terahertz source.
Applied Optics
|August 5, 2014
Summary
A novel tunable terahertz source was developed using quantum cascade laser upconversion. This compact device generates ultranarrowband radiation for spectroscopic applications.
Area of Science:
- Physics
- Spectroscopy
- Quantum Electronics
Background:
- Terahertz (THz) sources are crucial for spectroscopy and imaging.
- Existing THz sources often lack tunability and narrow linewidth.
- Compact and versatile THz generation methods are highly sought after.
Purpose of the Study:
- To demonstrate a compact, tunable, and ultranarrowband THz source.
- To achieve continuous tunability in specific frequency regions.
- To validate the source's performance using molecular rotational transitions.
Main Methods:
- Upconversion of a free-running quantum cascade laser (QCL) at 2.324 THz.
- Utilizing a THz Schottky-diode-balanced mixer driven by a swept microwave source.
- Characterization using a Fourier-transform spectrometer.
Main Results:
- Demonstration of a compact, tunable, ultranarrowband THz source with Δν∼1 MHz linewidth.
- Generation of 1 μW tunable radiation in two frequency bands: ν(Laser) ± 0–50 GHz and ν(Laser) ± 70–115 GHz.
- Successful tuning of the radiation through rotational transitions of CO, HDO, and D2O molecules.
Conclusions:
- The demonstrated method provides a viable approach for generating tunable, narrow-linewidth THz radiation.
- The compact source is suitable for high-resolution spectroscopy of molecular gases.
- This technology opens avenues for advanced THz applications requiring precise frequency control.
