Electrically switching transverse modes in high power THz quantum cascade lasers

Area of Science:

• Optoelectronics
• Quantum Engineering

Background:

• Terahertz (THz) quantum cascade lasers (QCLs) are crucial for various applications.
• Controlling the transverse mode and beam emission of THz QCLs is challenging.

Purpose of the Study:

• To design and fabricate a high-power THz QCL with electrically controllable transverse modes.
• To demonstrate dynamic beam switching using a symmetric side current injection scheme.
• To analyze the mode behavior under different bias conditions.

Main Methods:

• Fabrication of a high-power THz QCL.
• Implementation of a symmetric side current injection scheme for mode control.
• Measurements including angular-resolved L-I curves, near-field and far-field patterns, and angular-resolved lasing spectra.
• Two-dimension (2D) current and mode calculations.

Main Results:

• The quasi-TM(01) transverse mode dominates at lower current injection.
• The quasi-TM(00) mode lases at higher threshold current density and dominates at high current injection.
• Beam steering of 25 degrees in emission angle was achieved by changing current density from 1.9 kA/cm(2) to 2.3 kA/cm(2).

Conclusions:

• The developed THz QCL allows for electrically controlled transverse mode switching and dynamic beam steering.
• A 2D model successfully explains the observed mode behavior under varying bias conditions.
• This technology offers potential for advanced THz beam manipulation applications.