Phase-locked single-mode terahertz quantum cascade lasers array

We demonstrated a scheme of phase-locked terahertz quantum cascade lasers(THz QCLs) array, with a single-mode pulse power of 108 mW at 13 K. The device utilizes a Talbot cavity to achieve phase locking among five ridge lasers with first-order buried distributed feedback(DFB) grating, resulting in nearly five times amplification of the single-mode power. Due to the optimum length of Talbot cavity depends on wavelength, the combination of Talbot cavity with the DFB grating leads to better power amplification than the combination with multimode Fabry-Perot(F-P) cavities. The Talbot cavity facet reflects light back to the ridge array direction and achieves self-imaging in the array, enabling phase-locked operation of ridges. We set the spacing between adjacent elements to be 220 μm, much larger than the free-space wavelength, ensuring the operation of the fundamental supermode throughout the laser’s dynamic range and obtaining a high-brightness far-field distribution. This scheme provides a new approach for enhancing the single-mode power of THz QCLs.