Dual-wavelength pumped highly birefringent microstructured silica fiber for widely tunable soliton self-frequency shift

TL;DR

This paper presents a design for a highly birefringent microstructured silica fiber capable of widely tunable soliton self-frequency shifts when pumped at two common laser wavelengths, enabling access to previously unreachable wavelengths for applications like microscopy.

Contribution

The work introduces a universal fiber design supporting soliton shifts at two different pump wavelengths separated by over 500 nm, with high efficiency and polarization extinction.

Findings

Tunable soliton shifts up to 1.67 μm and 1.95 μm depending on pump wavelength.

Pump-to-soliton conversion efficiency exceeds 20%.

High polarization extinction ratio of 26 dB.

Abstract

We report the design of a microstructured silica-based fiber for widely tunable soliton self-frequency shift, suitable for pumping with two most common fiber laser wavelengths: 1.04 {\mu}m and 1.55 {\mu}m. Depending on the pump source, the output spectrum can be continuously tuned up to 1.67 {\mu}m (pump at 1.04 {\mu}m) or 1.95 {\mu}m (pump at 1.55 {\mu}m) in the same 1.5 m-long fiber sample, with pump-to-soliton conversion efficiency higher than 20%. The fiber is highly birefringent, which results in an excellent polarization extinction ratio of the soliton, reaching 26 dB. The shifted solitons have a high degree of coherence confirmed by pulse-to-pulse interference measurement. The available soliton tuning range covers the wavelengths inaccessible for fiber lasers, e.g., 1.3 {\mu}m and 1.7 {\mu}m, highly important for multi-photon microscopy and imaging. Our work shows that it is possible to design and fabricate one universal optical fiber that supports soliton shift when pumped at two different wavelengths separated by over 500 nm.