All-Fiber Filters for the Design of Tandem-Pumped Fiber Lasers

Introduction

In 2009, IPG Photonics achieved a groundbreaking accomplishment by demonstrating a 10 kW nearly single-mode fiber laser through a tandem-pumping configuration. Tandem pumping is recognized as one of the most promising techniques for enhancing the output power of single-mode fiber lasers operating at 1μm. This approach holds significant relevance for applications in the defense sector, like Directed Energy Weapons (DEW), as well as industrial applications such as cutting and welding, where the demand for very high-power fiber lasers exceeding 30 or 40 kW is growing.

Tandem-pumped fiber lasers at 1 micron

Tandem pumping involves the utilization of multiple pump sources at different wavelengths to efficiently stimulate the gain medium within the fiber. A common configuration of tandem-pumped ytterbium (Yb)-doped fiber lasers uses fiber lasers emitting at 1018 nm and pumped at 976 nm which in turn pump a Yb fiber laser typically operating at 1070 nm or 1080 nm, as shown in Figure 1.

However, designing tandem-pumped fiber lasers poses substantial challenges. Tandem-pumped 1-micron fiber lasers typically utilize forward pumping. At the 1018 nm wavelength, low absorption requires a longer active fiber length and larger core diameter, resulting in increased nonlinear effects.

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