Nonlinear absorption and Raman gain in helium-ion-implanted silicon waveguides

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Physics

Background:

• Free-carrier absorption is a significant loss mechanism in silicon photonics.
• Two-photon absorption generates free carriers, increasing losses, especially at higher optical powers.
• Existing methods to mitigate these losses, like reverse bias, add complexity and power consumption.

Purpose of the Study:

• To investigate helium ion implantation as a method to reduce carrier lifetime in silicon.
• To assess the impact of reduced carrier lifetime on free-carrier losses.
• To enable net gain in stimulated Raman scattering (SRS) without electrical carrier removal.

Main Methods:

• Helium ion implantation was performed on silicon waveguides.
• Carrier lifetime measurements were conducted.
• Experiments and theoretical modeling were used to analyze free-carrier losses and SRS gain.

Main Results:

• Helium ion implantation effectively reduced carrier lifetime in silicon.
• This reduction led to significantly lower free-carrier losses.
• Net gain was achieved via continuous-wave (cw)-pumped SRS, demonstrating the efficacy of the method.

Conclusions:

• Helium ion implantation is a viable technique to suppress free-carrier losses in silicon waveguides.
• This approach enables efficient stimulated Raman scattering gain without the need for reverse bias.
• The findings offer a promising pathway for advanced silicon photonic devices with reduced optical losses.