Study On Preparation Technology Of Sub-Wavelength Grating Reflector In VCSEL

The unique diffraction characteristics of sub-wavelength gratings make them widely used in various optical systems.In particular,the application of sub-wavelength gratings in vertical cavity surface emitting lasers（VCSELs）has received increasing attention in recent years.In order to improve the quality of the surface-emitting laser,reduce the difficulty of production,and improve the output characteristics,a high-contrast sub-wavelength grating（HCG）can be integrated on the VCSEL as a high-reflector mirror.However,since the process of fabricating sub-wavelength gratings is very complicated,it is necessary to study the preparation technology of sub-wavelength gratings.This dissertation focuses on the preparation of sub-wavelength grating mirrors in vertical cavity surface emitting lasers（VCSELs）.Firstly,the diffraction characteristics and reflectivity of the grating are calculated and analyzed using the strict coupled wave（RCWA）theory and the equivalent medium theory（EMT）.A TM-polarized sub-wavelength grating reflector for 2μm-band GaSb-based VCSELs was designed using Rsoft software based on the strictly coupled wave（RCWA）theory and has a large manufacturing tolerance.Based on the study of grating theory and the application mechanism of sub-wavelength gratings in VCSELs,the key technologies in the preparation of sub-wavelength grating mirrors are studied.The design process of sub-wavelength gratings is optimized through rational design experiments.The plasma-enhanced chemical vapor deposition（PECVD）method was used to fabricate a low-stress,high-quality SiO₂ film on a GaSb substrate with a large lattice mismatch as a low-refractive-index material layer for a high-contrast sub-wavelength grating.Then,a sub-wavelength grating pattern is prepared by a holographic lithography system with a stripe locking function,and the surface morphology of the grating pattern is tested by a scanning electron microscope（SEM）.The obtained grating pattern is relatively clear and flat and the stripe is continuous and uniform.Finally,the directional ICP technique is used to etch the sub-wavelength gratings,and the surface morphology of the scanning electron microscope（SEM）shows that the etched grating patterns are relatively clear and complete.Each parameter meets the design requirements.The prepared sub-wavelength grating mirrors were tested using a specific combination of infrared microscope systems.The test results show that it can achieve high reflectivity and wide bandwidth characteristics,thus providing technical support for laser lasing in GaSb-based VCSELs.