Laser compensation of optical waveguide shape defects on vertical end face

To address the issue of shape defects in optical waveguides that occur due to the laser beam being obstructed by the surface of the photonic chip during the vertical end-face waveguide bridging process in photonic chips. Based on the focusing light field of high numerical aperture (NA) objective lenses, the characteristics of light intensity distribution at various x-direction offset distances of the laser focus from the vertical end-face of the photonic chip are investigated. First, we give the analytical expressions of the light field near the focus. These are in the focusing system of high NA lenses. Firstly, analytical expressions for the light field distribution near the focal point in the focusing system of a high numerical aperture (NA) objective lens are presented, along with expressions for the components of the focused light field when linearly polarized light is incident. Then, numerical simulations are conducted with the provided expressions, the focal light intensity distribution of the laser focus at different x-direction offset distances from the vertical end-face of the photonic chip is studied. The intensity variations of the focal light field when subjected to disturbances are revealed, and curves depicting the intensity changes of the focal light field are plotted. These curves align with the observed trends in the shape changes of the optical waveguide during experiments. Finally, based on the focal light intensity distribution curves, the laser power compensation coefficients curves are derived in reverse. These are then applied to the optical waveguide compensation processing experiments. It can be seen that after power compensation processing, the sections of the optical waveguide with a width less than 4 μm are successfully compensated to 4 μm. Moreover, the morphology became straighter, and the defects are effectively repaired. The results of numerical calculation simulations and experiments demonstrate that this method successfully compensates for the shape defects of optical waveguides caused by insufficient laser power, providing an effective solution for the fabrication and processing of optical waveguides in the field of photonic chip integrated coupling.