We developed distributed-feedback (DFB) resonators based on single-plasmon waveguides and first-order lateral DFB (lDFB) gratings [Fig. 1(a)]. These lasers exhibit single-mode emission with output powers of a few mW at operating temperatures, which are accessible by compact Stirling coolers. Based on a rigorous solution of Maxwell’s equations for the DFB unit cell, we developed a general method to calculate the coupling coefficients of lDFB gratings. This allows for an efficient simulation of the resonator properties within the framework of the one-dimensional coupled-mode equations.
One goal for THz astronomy is the heterodyne spectroscopy of the neutral oxygen (OI) fine-structure transition at 4.745 THz, which requires a local oscillator just a few GHz beside this transition frequency. Based on an optimized heterostructure and an adjusted lDFB grating, we achieved single-mode, cw operation around the target frequency [Fig. 1(b)].