High energy and narrow linewidth N₂-filled hollow-core fiber laser at 1.4 μm

In this work, we develop a high energy laser at 1.4 μm wavelength through the 1st order vibrational Raman Stokes generation in a nitrogen (N₂) filled nodeless anti-resonant hollow core fiber (ARHCF), pumped using a custom-made 1060 nm Yb-doped narrow-linewidth fiber laser with 3.7 ns pulse duration and 98 μJ pulse energy. The maximum Raman energy of 26.5 μJ is achieved at 15 bar N₂ pressure, corresponding to a quantum efficiency of 45% and peak power of 8.03 kW with 3.3 ns pulse width. This Raman laser has a narrow linewidth of 0.16 nm, and it is tunable over ∼2 nm range by thermally tuning the laser diode seed wavelength of the pump fiber laser. This work provides a promising alternative for developing high energy and narrow-linewidth lasers outside the gain spectral regions of rare earth ion doped fibers.