Input/output optical couplers for ion-exchanged planar waveguides based on volume Bragg gratings in photo-thermo-refractive glass

Subject of study. Ion-exchanged optical waveguides and volume Bragg gratings in photo-thermo-refractive glass are studied. Aim of study. The aim of this study is to develop input/output couplers for planar ion-exchanged waveguides based on volume Bragg gratings in photo-thermo-refractive glass. Methods. Photo-thermo-induced crystallization was used to record a volume Bragg grating through ultraviolet laser exposure followed by thermal treatment at 500°C. Ion exchange in an AgNO ₃ salt melt at 350°C was subsequently applied to increase the surface refractive index and form a planar waveguide while preserving the Bragg grating. Main results. A monolithic structure combining a planar waveguide and volume Bragg grating was obtained. The volume Bragg grating was able to function as either an input or output element for the waveguide. Practical significance. Photo-thermo-refractive glass enables the combination of photo-thermo-induced crystallization and ion exchange technologies. The fabrication of input/output couplers and optical waveguide structures in the same material can reduce the number of bulky external optical elements and materials required in integrated optical systems while increasing functionality.