All-polarization-maintaining Nd-doped ultrafast fiber laser oscillator at 929 nm mode-locked via a 3x3 nonlinear amplifying loop mirror

Abstract

Successful generation of ultrashort pulses in the spectral region of 920 nm using Nd-doped fibers requires effectively suppressing the dominant 1064 nm four-level transition. Utilizing a hybrid design incorporating a W-shaped double-clad Nd-doped fiber and a single-clad Nd-doped fiber together with filtering out parasitic 1.06 µm beam, we developed an oscillator capable of delivering ultrashort pulses at the central wavelength of 929 nm. Here, we transferred the crucial components of the technology from the well-developed Yb-doped systems to build an all-polarization-maintaining Nd-doped fiber laser oscillator. The ultrashort pulsed operation is obtained through the passive mode-locking via a nonlinear amplifying loop mirror based on a 3x3 fiber coupler. The self-starting system has a figure-of-8 all-normal-dispersion cavity design and operates in a dissipative soliton regime. The oscillator, generating pulses with energy exceeding 1 nJ, delivers chirped 14.3 ps pulses, which can be compressed to 313 fs.