Fig. 3
From: Ultrafast switch-on dynamics of frequency-tuneable semiconductor lasers
Coherent time-domain measurement of the electric field emitted from the coupled-cavity laser with the tuning cavity switched off. a The electric field emitted from the output facet of the tuning cavity, measured as a function of time. The seed pulse enters the laser cavity at t = 0. The lasing cavity is driven using quasi-direct current pulses of amplitude 0.65 A and the tuning cavity is switched off. Inset: Close-up of the measured electric field and the variation of the amplitude of the terahertz field at t = 1500 ps as a function of voltage applied across the broadband photoconductive antenna. An increase in the terahertz field was measured with respect to antenna bias, before saturating at an antenna bias >2.5 V implying that the emission is fully injection seeded by the seed pulse. b Plot showing the dynamic variation of the emission spectra, obtained from the fast Fourier transform of the time-domain electric field using a moving time window of width 150 ps. The x-axis plots the beginning of this time window on a logarithmic scale to emphasise the presence of mode hopping during the initial few round-trips in the cavity. c Emission spectra obtained from the fast Fourier transform of the time-domain electric field using a ~460-ps-wide time window beginning at t = 400 ps (blue) and at 1700 ps (magenta)
