We show a fully integrated, coherently combined laser system in the InP-Si<sub>3</sub>N<sub>4</sub> hybrid platform. Coherent combining of two InP-based gain chips is obtained with a combining efficiency of ~92%. Besides, we demonstrate narrow-linewidth, tunable diode lasers in InP/GaAs-Si<sub>3</sub>N<sub>4</sub> platform. The Si<sub>3</sub>N<sub>4</sub> photonic integrated circuit performs as a tunable external cavity for both InP and GaAs gain chips simultaneously. Single frequency lasing at 1.55 and 1 um is simultaneously obtained on a single chip with the spectral linewidths of 18-kHz and 70-kHz respectively. We also obtain wide-angle beam steering by using the wide wavelength tuning range provided by dual-band diode lasers.
A new method for controlling the groove profiles of diffraction gratings which changes the etching angle and etching time, meanwhile divides the etching area in the substrate into multi-layers to have a good approximation for the theory is introduced. We put forward a multi-layers etching model on the base of the ion bean sputtering (IBS) which can calculate the etching time and etching angle. We test the curved grooves profiles and get the optimizations for the number of the multi-layers, etching time and etching time in this model. Also a photoresist grating is applied for the etching experiment. The results indicate that the optimized parameters such as the number of the multi-layers result in a smaller root mean square deviation (RMSD) between the theory and the real etching result which show good agreement with the theoretical groove within the variation of ±6% of the etching rate. The simulation predictions and experimental results show that the multi-layers etching model to control the groove profiles of diffraction gratings is available.