Beam Pattern Investigation of Terahertz Quantum Cascade Lasers

Far-fleld beam pattern measurement results of in-house fabricated 1mm long THz QCLs with ridge widths of 30"m and 100"m are presented. Both devices show difiractive-like beam patterns in the elevation direction (perpendicular to semiconductor heterojunction plane). In the in-plane direction (parallel to semiconductor heterojunction plane), the device with a wider ridge width (100"m) shows a quasi-Gaussian-like beam proflle. A radio-frequency (RF) design simulator (HFSS) is deployed to simulate far-fleld beam pattern of the QCL devices. The simulation results are in good agreement with the experimental results.