Enhancement of terahertz fields in LiTaO₃ waveguides using a conical pulse front

Area of Science:

• Physics
• Optics
• Materials Science

Background:

• Ultrafast electromagnetic pulses in the terahertz (THz) range are crucial for nonlinear THz spectroscopy and controlling molecular responses.
• Traditional THz spectroscopy setups (1-THz range) face challenges with large wavelengths, bulky components, and limited sample environments due to free-space propagation.

Purpose of the Study:

• To introduce a novel optical pumping geometry, terahertz ring excitation (TREx), for generating high THz fields within planar waveguides.
• To overcome limitations of conventional THz spectroscopy by enabling compact, waveguide-based experiments.

Main Methods:

• Utilized a terahertz ring excitation (TREx) optical pumping geometry.
• Generated superposing, focusing THz fields in planar waveguides made of lithium tantalate.
• Measured THz fields optically without free-space propagation.

Main Results:

• Achieved high THz field strengths exceeding 175 kV/cm.
• The TREx geometry generated THz fields approximately 20 times stronger than single-line focusing methods.
• Demonstrated THz field generation entirely within a waveguide structure.

Conclusions:

• The TREx technique enables the generation of significantly enhanced THz fields within compact waveguide structures.
• This method eliminates the need for free-space THz propagation, simplifying experimental setups.
• Opens new avenues for advanced, compact THz spectroscopy and signal processing applications.