Abstract
We report a continuous-wave highly-coherent and tunable dual-frequency laser emitting at two frequencies separated by 30 GHz to 3 THz, based on compact III–V diode- pumped quantum-well surface-emitting semiconductor laser technology. The concept is based on the stable simul- taneous operation of two Laguerre–Gauss transverse modes in a single-axis short cavity, using an integrated sub- wavelength-thick metallic mask. Simultaneous operation is demonstrated theoretically and experimentally by recording intensity noises and beat frequency, and time- resolved optical spectra. We demonstrated a >80 mW out- put power, diffraction-limited beam, narrow linewidth of <300 kHz, linear polarization state (>45 dB), and low in- tensity noise class-A dynamics of <0.3% rms, thus opening the path to a compact low-cost coherent GHz to THz source development.