Design and fabrication of InP-based diode lasers with short cavity lengths: Two-section and three-section configurations

This study presents the fabrication and characterization of short-cavity InGaAsP/InP (1330 nm) and AlGaInAs/InP (1550 nm) multisection diode lasers with two-section (gain and absorber) and three-section (two gain and one absorber) configurations. Smooth and anisotropic etching of surface and sidewall structures was achieved using CH4/H2/Cl2 gas mixtures in the waveguide etching process, conducted without heating. The fabrication process was analyzed by scanning electron microscopy, optical microscopy, and 3D profilometry to evaluate etching quality. Depending on the gas used, the smoothest surface structure with an average roughness (Ra) of 0.137 μm and the most anisotropic profile of ∼90° were achieved. The performance of the fabricated lasers was assessed through light-current (L-I), current-voltage (I-V), and optical spectral analysis. The InGaAsP/InP laser (1330 nm) exhibited a threshold current of 2 mA, while the AlGaInAs/InP laser (1550 nm) demonstrated a threshold current of 5 mA. These results demonstrate the effectiveness of the proposed heating-free fabrication approach and confirm its suitability for compact multisection InP-based diode laser devices.