All-fiber 2 μm high-order-mode light-source based on reconfigurable mode conversion

We demonstrate an all-fiber reconfigurable high-order-mode light-source generation around 2 μm waveband, which is realized using Tm-doped fiber, multiple-ring few-mode fiber, and alloyed waveguide grating. Mode conversion is carried out by applying loaded pressure on the alloyed waveguide grating, where the applied pressure transfers to the multiple-ring few-mode fiber uniformly. With a 13.0 MPa loaded pressure applied, a smooth spectrum ranging from 1944 nm to 2074 nm for the first high order mode (LP₁₁ mode) is generated as a high order mode light source with a peak power of −32.0 dBm at 2019 nm. The proposed high-order-mode light-source can convert the fundamental mode to any higher order mode by adjusting the alloyed waveguide grating period. The proposed high-order-mode light source in the mid-infrared wavelength band could be a powerful light source for the field of large capacity optical communication and sensing applications.