Gain evaluation of compact designing on Er 3+/Yb 3+ codoped germanate glass channel waveguide

Abstract

Bent waveguide structures (U- and F-bend) based on UV-sensitive Er 3+/Yb 3+ codoped germanate glass substrates have been designed to achieve high-gain C-band amplification. Using simulated-bend method, the optimal radius for curved structure is offered to be 1.90 cm with loss coefficient of 0.0015 dB/cm, as the substrate size is minimally schemed. In the wavelength range of 1528–1559 nm, obvious gain enhancement for the bent structure waveguides is anticipated, while, for the F-bend waveguide, the internal gain at 1533.8 nm wavelength is derived to be 22.55 dB, which is much higher than the value of 14.06 dB in the U-bend waveguide, and over three times higher than that of the straight one, after compensating both the bend loss and the transition loss. The simulation results indicate that the bent structure designing is beneficial in attaining high optical gain in Er 3+/Yb 3+ codoped germanate glass substrates, which assures that long-period grating can be applied to implement practical C-band gain-flattened amplification.