Tunable narrowband terahertz generation in lithium niobate crystals using a binary phase mask

Area of Science:

• Physics
• Optics
• Materials Science

Background:

• Terahertz (THz) generation is crucial for various spectroscopic and imaging applications.
• Optical rectification in nonlinear crystals offers a pathway for THz wave generation.
• Controlling THz spectral properties requires advanced techniques for phase matching and frequency tuning.

Purpose of the Study:

• To present a simple and effective scheme for narrowband terahertz (THz) generation.
• To demonstrate tunable THz frequency generation using optical rectification in lithium niobate.
• To showcase an application of the generated THz source for material characterization.

Main Methods:

• Utilizing optical rectification in a lithium niobate crystal.
• Employing a binary phase mask to create a patterned quasi-phase-matching structure.
• Spatiotemporal shaping of femtosecond (fs)-laser pulses for THz generation.
• Tuning THz frequency by adjusting imaging magnification of the mask in the crystal.

Main Results:

• Achieved narrowband THz generation with tunable frequency from 0.4-1.0 THz.
• Demonstrated that crystal illumination with shaped fs-laser pulses creates a patterned quasi-phase-matching structure.
• Observed an increase in THz-wave linewidth with decreasing optical beam size on the mask.
• Successfully applied the THz source to measure the transmittance of superconducting NbN thin films.

Conclusions:

• The presented scheme offers a simple method for generating tunable narrowband THz radiation.
• The technique effectively utilizes optical rectification and phase masks for controlled THz emission.
• The developed THz source is suitable for applications such as material characterization in cryogenic environments.