A simple optical spectral calibration technique for pulsed THz sources.

Area of Science:

• Optics and Photonics
• Quantum Electronics
• Spectroscopy

Background:

• Pulsed terahertz (THz) radiation is crucial for various scientific applications.
• Accurate spectral characterization of THz pulses is essential for understanding and utilizing THz sources.
• Existing methods for THz spectral measurement can be complex or lack single-shot capabilities.

Purpose of the Study:

• To quantify the sensitivity of a novel, simple method for measuring the frequency spectrum of pulsed THz radiation.
• To demonstrate a technique for direct spectral characterization of THz pulses without adjustable optical elements.
• To validate the method's performance with low-energy THz pulses.

Main Methods:

• Utilizing optical upconversion of THz pulses to the optical regime via sideband generation in a zinc telluride (ZnTe) crystal.
• Employing a continuous-wave (cw) narrow-bandwidth near-infrared laser for upconversion.
• Performing single-shot spectral measurements of the generated optical sideband pulses using a high-resolution spectrometer.

Main Results:

• The method directly provides the spectral information of THz pulses without requiring adjustable elements in the detection setup.
• Successful characterization of THz pulse trains (5 μs duration, 800 nJ integrated energy) and single pulses (as low as 13 nJ) at 150 μm wavelength (2 THz).
• Quantified sensitivity of the simple THz spectral measurement technique.

Conclusions:

• The presented method offers a straightforward and sensitive approach for single-shot spectral characterization of pulsed THz radiation.
• This technique is effective even for low-energy THz pulses, expanding the applicability of THz spectroscopy.
• The method's direct spectral readout simplifies THz source characterization and analysis.