Multiple-Beam Terahertz Laser Self-Mixing Interference and Its Application in Film Thickness Measurements

In this work, we study the multi-beam self-mixing interference in a terahertz quantum cascade lasers. The simulations demonstrate that both the amplitude and the phase of the multi-beam self-mixing signals depend on the displacement of the targets. Then the experiment demonstrates the possibility of film thickness measurement by multi-beam self-mixing. These results give the theoretical and experimental foundations to develop terahertz tomography based on multi-beam self-mixing interference of THz lasers.