Silver-based surface plasmon waveguide for terahertz quantum cascade lasers.

Area of Science:

• Optoelectronics
• Semiconductor devices

Background:

• Terahertz-frequency quantum cascade lasers (THz QCLs) are crucial for various applications.
• Traditional THz QCLs often use gold-based waveguides, limiting performance.
• Exploring alternative materials like silver is essential for advancing THz QCL technology.

Purpose of the Study:

• To investigate the theoretical and experimental performance of THz QCLs using silver waveguide layers.
• To compare silver-based THz QCLs with traditional gold-based devices.
• To analyze the impact of waveguide material on THz QCL performance.

Main Methods:

• Theoretical simulations of threshold gain and waveguide losses for silver, gold, and copper.
• Experimental fabrication and testing of THz QCLs with silver and gold surface-plasmon waveguides.
• Analysis of device performance, including operating temperature and output power.

Main Results:

• Silver-based waveguides demonstrate lower losses for THz QCLs across practical temperatures and frequencies.
• Experimentally, silver-based THz QCLs exhibited a 5 K increase in maximum operating temperature and a 40% increase in output power.
• Performance improvements were dependent on active region design, with greater gains for higher radiative diagonality.

Conclusions:

• Silver-based waveguide structures offer significant advantages for THz QCLs.
• These findings suggest silver can enable high-temperature operation of THz QCLs.
• The results pave the way for more efficient and powerful THz QCL devices.