Electrically pumped semiconductor laser with monolithic control of circular polarization

Area of Science:

• Optics and Photonics
• Semiconductor Devices
• Terahertz (THz) Technology

Background:

• Terahertz (THz) radiation generation and manipulation are crucial for various applications.
• Controlling the polarization of THz emission is essential for advanced functionalities.
• Quantum cascade lasers (QCLs) are efficient sources of THz radiation.

Purpose of the Study:

• To demonstrate surface emission of THz radiation from a monolithic quantum cascade laser.
• To achieve built-in control over the degree of circular polarization of THz emission.
• To introduce and evaluate novel grating concepts for polarization control.

Main Methods:

• Utilized monolithic quantum cascade lasers.
• Designed and fabricated "fishbone" gratings with orthogonally oriented aperture antennas.
• Performed simulations and experimental measurements of THz emission characteristics.
• Investigated fifth-order and transverse grating designs.

Main Results:

• Achieved high degrees of circular polarization up to 86% with fifth-order gratings in a 12° emission lobe.
• Demonstrated degrees of circular polarization as high as 98% with transverse gratings in specific far-field regions.
• Validated simulation results with experimental data.

Conclusions:

• Integrated antenna gratings offer effective control over THz polarization.
• The demonstrated gratings enable high-performance, polarization-controlled THz surface emission.
• Potential and limitations of these integrated gratings for polarization-controlled THz emission were discussed.