A polarization-insensitive plasmonic photoconductive terahertz emitter

Area of Science:

• Optics and Photonics
• Terahertz Science and Technology
• Materials Science

Background:

• Photoconductive terahertz emitters are crucial for terahertz (THz) applications.
• Existing plasmonic photoconductive emitters often exhibit polarization-dependent performance, limiting their practical use.
• Optimizing optical pump absorption and electrode geometry is key to enhancing THz emission efficiency.

Purpose of the Study:

• To design and demonstrate a polarization-insensitive plasmonic photoconductive terahertz emitter.
• To investigate the effect of nanoscale cross-shaped apertures on THz emission.
• To compare the performance of the new emitter with existing polarization-sensitive designs.

Main Methods:

• Fabrication of a terahertz emitter utilizing a two-dimensional array of nanoscale cross-shaped apertures as plasmonic contact electrodes.
• Optimization of the cross-shaped aperture geometry for maximal optical pump absorption near electrodes.
• Experimental characterization of terahertz radiation generated by femtosecond optical pumping.
• Comparison of terahertz radiation power across different optical pump polarizations.

Main Results:

• The developed emitter demonstrates polarization-insensitive terahertz radiation.
• The cross-shaped aperture geometry ensures uniform optical pump absorption regardless of polarization.
• Achieved terahertz radiation powers are comparable to polarization-sensitive emitters at their optimal polarization.
• The two-dimensional symmetry of the apertures is critical for polarization-insensitive operation.

Conclusions:

• The novel plasmonic photoconductive terahertz emitter with cross-shaped apertures offers robust, polarization-insensitive THz generation.
• This design overcomes the polarization dependency limitations of previous plasmonic THz emitters.
• The findings pave the way for more versatile and user-friendly terahertz systems.