Fig. 1. Schematic of the 4 × 5 interleaving matrix-grating REC-DFB MLA (SCH-MQW, separate confinement hetero-structure multiple quantum well; BG, Bragg grating).

Fig. 2. Transmission spectra of the designed five in-series gratings (LD1, LD5, LD9, LD13, and LD17) and the five transmission peaks marked with red triangles corresponding to the lasing modes of the five in-series element lasers.

Fig. 3. Schematic of the (a) DFB laser packaging configuration and the (b) top view of the 4 × 5 interleaving matrix-grating REC-DFB laser array mounted on the submount integrated with heaters (NTC thermistor, negative temperature coefficient thermistor).

Fig. 4. Thermal simulations of the REC-DFB MLA chip’s steady-state temperature on the (a) standard AlN submount and the (b) optimized submount integrated with thin-film heaters, with laser injected current of 80 mA and heater injected current of 190 mA. Enlarged view of the temperature distributions for the REC-DFB MLA chip on the (c) standard AlN submount and the (d) submount integrated with thin-film heaters.

Fig. 5. (a) Microscopic view of the 4 × 5 interleaving matrix-grating REC-DFB laser array chip; (b) top view and (c) magnified view of the fabricated 4 × 5 matrix-grating REC-DFB laser array chip on AlN submount integrated with TaN film heaters.

Fig. 6. (a) Superimposed lasing spectra of all 20 lasers when the laser current is 80 mA and (b) the lasing wavelength fitting for the 20 element lasers of the REC-DFB MLA, with the wavelength-fitting deviations of the 20 lasers depicted in the inset of (b).

Fig. 7. (a) Typical PI and IV diagram of the four in-parallel lasers with SOA and optical combiner injection current of 20 mA and 50 mA. (b) Output powers of all 20 lasers with the SOA current varied from 0 to 100 mA as well as the optical combiner injection current of 50 mA and laser current of 80 mA (I_LD, the injection current of laser; I_SOA, the injection current of the semiconductor optical amplifier).

Fig. 8. Measured tuning spectra and current-wavelength relationships for the 20 lasers of the REC-DFB MLA mounted on the standard submount and the optimized submount with thin-film heaters, respectively.

Fig. 9. Experimentally measured central reflection wavelength of the same FBG for repeating wavelength-tuning experiments by 16 times.

Fig. 10. Experimentally measured tuning speed of the (a) TEC tuning scheme and (b) submount heater tuning scheme for 2.5 nm wavelength variations of one element laser using the MZI-based system.