Continuous-wave Raman amplification in silicon core fibers pumped in the telecom band

Meng Huang,Shiyu Sun,Dong Wu,Thomas W Hawkins,John Ballato,Haonan Ren,Anna C Peacock,Li Shen,Ursula J Gibson

doi:10.1063/5.0060108

Abstract

Stimulated Raman amplification is observed for the first time in the silicon core fiber (SCF) platform. The SCFs were tapered to obtain sub-micrometer core dimensions and low optical transmission losses, facilitating efficient spontaneous scattering and stimulated Raman amplification using a continuous-wave pump source with milliwatt power levels. A maximum on–off gain of 1.1 dB was recorded at a pump power of only 48 mW with our numerical simulations, indicating that gains up to 6dB are achievable by increasing the fiber length. This work shows that the SCF platform could open a route to producing compact and robust all-fiber integrated Raman amplifiers and lasers across a broad wavelength region.

Highlights

Raman scattering offers a convenient route to developing amplifiers and light sources from waveguide materials that do not possess a direct bandgap
The silicon core fiber (SCF) are typically fabricated via the molten core drawing (MCD) method, which allows for the rapid production of long lengths of fiber, increasing the device yield and lowering production costs
The SCFs used in this work were fabricated using the MCD method, which is based on conventional fiber drawing techniques whereby the low melting temperature semiconductor core is encapsulated in the softened silica cladding

Summary

INTRODUCTION

Raman scattering offers a convenient route to developing amplifiers and light sources from waveguide materials that do not possess a direct bandgap. To reduce the linear losses, waveguides with large, micrometer-sized dimensions have been employed, but these have required the use of impractically high coupled pump powers [∼1 W continuous-wave (CW)] to achieve Raman gains up to 2.3 dB due to the reduced light confinement.. With advancements to the fabrication techniques, the small core SCFs can be produced to exhibit low losses over centimeter lengths, opening a route to obtaining effective levels of Raman gain using modest CW pump powers. Compared to their planar counterparts, the SCFs offer several advantages for practical systems as they are robust and polarization independent, and they can be spliced directly to fiber pump lasers and networks.. We anticipate that with continued efforts to reduce the transmission losses over longer lengths, these SCFs could open new possibilities for all-fiber Raman-based laser sources and amplifiers

FIBER FABRICATION AND NONLINEAR PROPAGATION EQUATION

Experimental setup

Spontaneous Raman emission

Stimulated Raman amplification

CONCLUSION