Theoretical investigation of the more suitable rare earth to achieve high gain in waveguide based on silica containing silicon nanograins doped with either Nd3+ or Er3+ ions

TL;DR

This study compares the gain potential of silica waveguides doped with Nd3+ or Er3+ ions, revealing Nd3+ offers significantly higher gain and feasible net amplification under realistic conditions.

Contribution

The paper introduces a novel ADE-FDTD simulation method to analyze and compare the gain in silica waveguides doped with Nd3+ and Er3+ ions, highlighting the superior performance of Nd3+.

Findings

Nd3+ doped waveguides achieve up to 30 dB/cm gain at 1064 nm.

Er3+ doped waveguides reach up to 2 dB/cm gain at 1532 nm.

Significant positive net gain is only feasible with Nd3+ doping considering background losses.

Abstract

We present a comparative study of the gain achievement in a waveguide whose active layer is constituted by a silica matrix containing silicon nanograins acting as sensitizer of either neodymium ions (Nd3+) or erbium ions (Er3+). By means of an auxiliary differential equation and finite difference time domain (ADE-FDTD) approach that we developed, we investigate the steady states regime of both rare earths ions and silicon nanograins levels populations as well as the electromagnetic field for different pumping powers ranging from 1 to 104 mW/mm2. Moreover, the achievable gain has been estimated in this pumping range. The Nd3+ doped waveguide shows a higher gross gain per unit length at 1064 nm (up to 30 dB/cm) than the one with Er3+ doped active layer at 1532 nm (up to 2 dB/cm). Taking into account the experimental background losses we demonstrate that a significant positive net gain can only be achieved with the Nd3+ doped waveguide.