In this article we demonstrate the first, to the best of our knowledge, all-fiber self-starting laser oscillator consisting entirely of polarization-maintaining large mode area (PLMA) fibers mode-locked with nonlinear optical loop mirror (NOLM). The system works in a Raman-free dissipative soliton regime and operates at a central wavelength of 1030 nm. It delivers stable ultrashort pulses of high energy of 12 nJ at a 7.56 MHz repetition rate which can be compressed down to the Fourier transform limit of ~250 fs. Higher energies were limited by the formation of multiple pulses in the cavity.

Chirped fiber Bragg gratings in Yb-doped fiber lasers allow tuning the net cavity dispersion, thus enabling access to pulse dynamics beyond the typical all-normal-dispersion dissipative soliton regime. This Letter demonstrates an ultrafast dispersion-managed all-polarization-maintaining fiber oscillator mode-locked with a nonlinear optical loop mirror. Using a chirped fiber Bragg grating inside the oscillator, it can work at net cavity dispersion in the range from $-0.098\,\,\mathrm {ps^{2}}$ up to $+ 0.067\,\,\mathrm {ps^{2}}$ and above at the wavelength of $1~\mu \text{m}$ . Depending on the configuration, the system can deliver stable pulses with energies up to 2.3 nJ and pulse durations as short as 98 fs.

Ultrafast fiber oscillators based on loop mirror saturable absorbers often suffer from a problematic self-starting mode-locking operation. It is usually necessary to provide an additional phase shift in the loop, guaranteeing repeatable initiation of the pulsed regime. 3x3 even splitting ratio fiber couplers have recently introduced a required phase shift in an all-fiber loop mirror architecture. Until now, mode-locking induced by a 3x3 fiber coupler has been associated only with nonlinear amplifying loop mirrors. Here, we present a self-starting ultrafast dispersion-managed all-polarization-maintaining Yb-doped oscillator that utilizes a nonlinear optical lossy loop mirror instead. We show three ways of inserting asymmetric losses in a loop via a variable optical attenuator, a fiber coupler, and a very simple lossy splice. Complete characterization of all output ports of the oscillator proves significant spectral and temporal breathing of the pulse when circulating through the net normal dispersion cavity, which can deliver nJ-level pulse energy. The system guarantees excellent stability, low noise and performance comparable to nonlinear amplifying loop mirrors while being simpler, cheaper, and providing more usable output ports with different pulse characteristics.

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.

Ultrafast all-fiber Yb-doped fiber oscillators are usually associated with all-normal-dispersion cavities, which operate in a dissipative soliton regime, quintessential for pulsed operation at the wavelength of 1 $\mu$ m. This work presents an all-polarization-maintaining Yb-doped fiber laser oscillator that operates in a dispersion-managed dissipative soliton regime, thanks to incorporating a chirped fiber Bragg grating. The oscillator, mode-locked via a nonlinear optical loop mirror, has an unconventional semi-linear cavity of net anomalous dispersion. Unlike in standard ring resonators, the ultrashort pulse undergoes amplification twice per cavity roundtrip. Additionally, we report a duality of pulsed operation states depending on the pumping power. Strikingly, the oscillator can work in a subregime similar to the standard dissipative soliton, facilitating further energy scaling at anomalous dispersion. We characterize the low-noise setup capable of delivering pulse energy as high as 6.4 nJ using standard single-mode polarization-maintaining optical fibers.