Polarization analysis of random THz lasers

By varying the geometrical filling factor from 8% to 12% and the hole radius from 3 to 5 µm, we investigate the interference pattern of a set of surface emitting, electrically pumped random lasers (RLs) at terahertz frequencies employing a surface pattern of random holes, studying the polarization of the emitted modes, the spectral emission, and the power extraction. By funneling the laser beams onto a wire grid polarizer, we demonstrate spectral reshaping of the RL emission and of the far-field profile, achieving highly collimated emission (5° × 3° angular divergence) and a spectral coverage of 340 GHz with up to 11 random lasing modes. The polarization analysis of the far-field and spectral characteristics of the laser offer an interesting tool to investigate the complex behavior of quantum cascade RLs, providing a route to engineer the emission of RLs in more detail.