Fig. 2: Soliton microcomb generation with a gain-switched distributed feedback laser.
From: Gain-switched semiconductor laser driven soliton microcombs
a The GSL spectra when the master laser is injected at the central lasing position (upper panel) and an off-central-mode frequency (lower panel). The grey stripes indicate the positions of the two adjacent longitudinal modes. The red dashed lines show the wavelengths of the master laser. b The intensity autocorrelation of the GSL pulses when the DFB laser is central-mode-injected (upper panel) and off-centre-injected (lower panel), respectively. c Laser downsweeping transmission traces corresponding to the central-mode-injected operation (upper panel) and off-centre-injected operation (lower panel), respectively. In the lower panel, 100 consecutive sweeping traces are overlaid. The offset-centre injection locking leads to significantly longer soliton steps. d, e The microcomb spectra of a Si3N4 microring resonator and an MgF2 crystalline resonator. The left-hand insets show the enlarged portions of the spectra (band-pass-filtered for the Si3N4 microcomb). The right-hand insets are the photographs of the microresonators. f Contour plot of the laser-frequency-swept transmission as the gain-switching frequency fgs is varied. The trapezium outlined by dashed lines indicates the area for a robust single-soliton generation. g Spectra of frep when the laser-resonance detuning is swept, showing that the microcomb repetition frequency is changing in CW pumping but governed by fgs in the GSL-driven situation. The measurement resolution bandwidth (RBW) is 100 Hz.
