We present results achieved in the generation of terahertz wave by a semiconductor laser. It is a
Fabry–Pérot based device with shallow grooves implemented on its p-side to engineer the longitudinal mode spectrum. The laser is dc-biased and temperature controlled at 298 K. The main
two modes are separated by 3 nm at 1550 nm with a side-mode-suppression ratio of 25 dB. Using
a frequency resolved optical gating, evidence of mode beating at 373 GHz is observed. With a
bolometer interfaced to a Fourier transform interferometer, the second harmonic signal is measured
at 690 GHz.