Photonic crystal fiber with large-mode area and low bending loss for high-power compact lasers and amplifiers

We report on a flexible large mode area (LMA) photonic crystal fiber (PCF) for high power laser and amplifier applications. We designed a fiber cross-section that includes two regions with different air-filling factors on opposite sides of the fiber core. This design allows suppressing higher order modes (HOMs) when the fiber is bent around a 10 cm radius at a wavelength of 1064 nm. The fiber then exhibits single-mode (SM) operation within a very large core with a diameter larger than 60 mu m. The loss of the fundamental mode (FM) is lower than 0.01 dB/m. We can therefore consider building compact high power fiber lasers and amplifiers with a nearly diffraction limited beam output using our LMA PCF.