Terahertz generation by optical rectification in lithium niobate crystal using a shadow mask

Area of Science:

• Physics
• Optics
• Materials Science

Background:

• Terahertz (THz) radiation generation is crucial for spectroscopy and imaging.
• Existing methods often lack tunability in frequency and bandwidth.
• Optical rectification (OR) offers a promising route for THz generation.

Purpose of the Study:

• To propose and demonstrate a simple method for generating tunable multicycle THz pulses.
• To achieve control over both the frequency and bandwidth of THz pulses.
• To investigate the energy spectral density of the generated THz pulses.

Main Methods:

• Utilizing optical rectification (OR) of spatially shaped femtosecond laser pulses.
• Employing a one-dimensional binary shadow mask for laser beam shaping.
• Using a lithium niobate (LN) crystal for THz generation.
• Tuning THz frequency by varying demagnification of the mask's image in the LN crystal.
• Adjusting THz bandwidth by changing the optical beam size on the crystal.

Main Results:

• Demonstrated tunable THz generation with frequencies ranging from 0.3 to 1.2 THz.
• Achieved tunable THz bandwidth from 20 GHz to approximately 1 THz.
• Observed an energy spectral density of 0.18 μJ/THz for narrowband THz generation with ~1 W pump power at 1 kHz repetition rate.
• Showcased the independence of energy spectral density from bandwidth for narrowband THz generation.

Conclusions:

• The proposed method provides a simple and effective way to generate tunable multicycle THz pulses.
• Spatially shaping femtosecond laser pulses offers precise control over THz output characteristics.
• This technique holds potential for applications requiring tailored THz radiation.