Bent channel design in buried Er³⁺/Yb ³⁺ codoped phosphate glass waveguide fabricated by field-assisted annealing

Bent waveguide structures (S-, U-, and F-bend) based on buried Er ³⁺/Yb³⁺ codoped phosphate glass waveguide channel fabricated by field-assisted annealing have been designed to achieve high-gain C-band integrated amplification. Using a simulated-bend method, the optimal radius for the curved structure is derived to be 0.90 cm with loss coefficient of 0.02 dB/cm, as the substrate size is schemed to be 4×3 cm². In the wavelength range of 1520 to 1575 nm, obvious gain enhancement for the bent structure waveguides is anticipated, and for the F-bend waveguide, the internal gain at 1534-nm wavelength is derived to be 41.61 dB, which is much higher than the value of 26.22 and 13.81 dB in the U- and S-bend waveguides, respectively, and over three times higher than that of the straight one. The simulation results indicate that the bent structure design is beneficial in obtaining high signal gain in buried Er^{3 +}/Yb³⁺ codoped phosphate glass waveguides, which lays the foundation for further design and fabrication of integrated devices.