Distributed-feedback terahertz quantum-cascade lasers with laterally corrugated metal waveguides

Area of Science:

• Optics and Photonics
• Semiconductor Devices
• Quantum Electronics

Background:

• Quantum cascade lasers (QCLs) are crucial for generating coherent terahertz (THz) radiation.
• Distributed feedback (DFB) mechanisms are essential for single-mode emission in lasers.
• Previous THz QCL designs faced challenges in achieving stable, single-mode operation.

Purpose of the Study:

• To demonstrate a novel distributed-feedback terahertz quantum-cascade laser.
• To investigate the impact of a first-order grating fabricated via lateral corrugation.
• To precisely control facet reflection phase for improved laser performance.

Main Methods:

• Fabrication of a double-sided metal ridge waveguide with a first-order grating.
• Utilizing lithographically defined facets created by dry etching for precise phase control.
• Conducting finite-element simulations to analyze modal and threshold characteristics.

Main Results:

• Achieved single-mode emission at low to moderate injection currents.
• Observed multimode emission beyond the threshold due to spatial hole burning.
• Experimental results showed good agreement with finite-element simulation predictions.

Conclusions:

• The demonstrated DFB THz QCL design with a lateral corrugation grating is effective for single-mode operation.
• Precise control over facet reflection phase is critical for laser performance.
• The study validates the use of finite-element simulations for predicting device characteristics.