Fig. 2: Laser characterization.
From: High-performance lasers for fully integrated silicon nitride photonics
a LI measurements of three lasers with different gain section length (1.5 mm or 2.5 mm) and grating κ values (0.25 cm−1, 0.75 cm−1, and 0.875 cm−1). b Corresponding grating reflection response of lasers measured in (a). c Optical spectrum of the high-power laser (shown in blue in a and b) at a gain current of 300 mA. The optical spectrum analyzer resolution bandwidth is 0.02 nm. d Single-mode and multimode regimes as the wavelength are red-tuned across a mode-hop cycle, commonly observed in DBR lasers29, 35. The corresponding laser gain currents from left to right are 254.4, 258, and 261 mA, respectively. e Laser frequency noise spectrum of lasers with low-frequency noise and either kHz or sub-kHz level fundamental linewidth. The laser currents are 252.3 mA (purple), 382.2 mA (red) and 298 mA (green). Inset shows current-dependent high-offset frequency noise spectra for the laser with 2.5 mm gain section length and 1.5 cm−1 grating κ value (purple), indicating sub-kHz level Lorentzian linewidth is achieved for all three currents. f Laser RIN measurements of a low-threshold laser (shown in green in a and b) and another laser (shown in purple in e).
