Wavelength beam-combining of terahertz quantum-cascade laser arrays

Wavelength beam-combining of four terahertz (THz) distributed-feedback quantum-cascade lasers (QCLs) is demonstrated using low-cost THz components that include a lens carved out of a plastic ball and a mechanically fabricated blazed grating. Single-lobed beams from predominantly single-mode QCLs radiating peak power in the range of 50-170 mW are overlapped in the far field. at frequencies ranging from 3.31-3.54 THz. Collinear propagation with a maximum angular deviation of 0.3 degrees is realized for the four beams. The total power efficiency for the focused and beam-combined radiation is as high as 25%. This result could pave the way for future commercialization of beam-combined monolithic THz QCL arrays for multi-spectral THz sensing and spectroscopy at standoff distances. (C) 2021 Optical Society of America