Fig. 1. Schematic diagram of femtosecond laser processing waveguide Bragg grating system

Fig. 2. Single-line microscopic images inscribed under different pulse energies. (a) Top view; (b) cross-sectional view

Fig. 3. Design drawings and topographies. (a) Structural design drawing of DCW; (b) structural design drawing of WBG; (c) top view of WBG; (d) cross section of WBG with grating at center of waveguide

Fig. 4. Schematic diagram of end-coupling system

Fig. 5. Optical microscope cross sections of waveguides and corresponding mode profiles with scale of 10 μm

Fig. 6. Waveguide length versus total loss

Fig. 7. Experimental diagram of spectral response characterization of WBG

Fig. 8. Spectra of WBGs with different lengths. (a)(b)Reflectance spectra; (c)(d) transmission spectra with insets showing grating length versus reflectivity

Fig. 9. Spectra of 10 mm long waveguide Bragg grating. (a) Reflectance spectrum; (b) transmission spectrum

Fig. 10. Changes in WBG reflection spectra during warming. (a) TE mode; (b) TM mode

Fig. 11. WBG center wavelength versus temperature at different temperatures. (a) TM mode; (b) TE mode