Fig. 1. Waveguide structure and TM₀₀ mode profiles. (a) Schematic of ridge waveguide structure; (b) TM₀₀ mode profile for fundamental light at 1560 nm; (c) TM₀₀ mode profile for frequency-doubled light at 780 nm

Fig. 2. Preparation of PPLN waveguide. (a) Preparation flowchart; (b) SEM image of periodically poled waveguide; (c) SEM image of waveguide end face

Fig. 3. Frequency-doubling experimental setup of PPLN waveguide

Fig. 4. Tuning curve of PPLN waveguide

Fig. 5. Output power and internal conversion efficiency of PPLN waveguide

Fig. 6. Measurement setup for single-port fiber-coupled PPLN waveguide

Fig. 7. Test of residual fundamental-frequency light. (a) Power curve of residual fundamental-frequency light; (b) mode pattern of residual fundamental-frequency light when P1L=5W

Fig. 8. Mode curves of PPLN waveguide. (a) Single-mode condition of PPLN waveguide when H = 7 μm; (b) mode cutoff curves of PPLN waveguide

Fig. 9. High power stability of PPLN waveguide frequency conversion device