Wavelength beam-combining of terahertz quantum-cascade laser arrays

Area of Science:

• Optics and Photonics
• Quantum Electronics
• Terahertz Technology

Background:

• Terahertz (THz) quantum cascade lasers (QCLs) are crucial for various applications.
• Efficient beam-combining of multiple THz QCLs is challenging but necessary for increased power and functionality.
• Existing methods often rely on complex and costly optical components.

Purpose of the Study:

• To demonstrate wavelength beam-combining of four THz distributed-feedback quantum cascade lasers (QCLs).
• To utilize low-cost, readily available THz components for beam combination.
• To achieve collinear propagation and high power efficiency for the combined THz beams.

Main Methods:

• Utilized four predominantly single-mode THz QCLs operating between 3.31-3.54 THz.
• Employed a lens carved from a plastic ball and a mechanically fabricated blazed grating for beam manipulation.
• Overlapped single-lobed beams in the far field to achieve collinear propagation.

Main Results:

• Successfully demonstrated wavelength beam-combining of four THz QCLs.
• Achieved collinear propagation with a maximum angular deviation of 0.3 degrees.
• Reached a total power efficiency of 25% for the focused and beam-combined radiation.
• Individual QCLs radiated peak power between 50-170 mW.

Conclusions:

• The developed method offers a cost-effective approach for THz QCL beam combining.
• This technique could enable the commercialization of monolithic THz QCL arrays.
• The results pave the way for advanced multi-spectral THz sensing and spectroscopy systems.