31 nJ sub-200 fs pulse generation from an Erbium-doped fiber amplifier similariton oscillator

Abstract

We demonstrated the highest femtosecond pulse energy from Erbium-doped fiber similariton or dissipative soliton oscillators (to our best knowledge). The output spectrum can be manipulated by waveplates and filter to support 86 fs transform-limited pulse.OCIS codes: (320.7090) Ultrafast lasers; (320.7110) Ultrafast nonlinear optics; IntroductionSub-picosecond pulse up to 1 J has been produced by Ytterbium-doped fiber oscillators based on large-mode-area fiber and dissipative soliton [1]. Unfortunately, the pulse energy of the Erbium counterparts is much weaker due to (1) the erbium-doped fiber (EDF) core has to be small (subject to strong nonlinearity) to achieve normal dispersion at the lasing wavelength (~1.5 m), (2) longer EDF is normally needed to provide high gain due to the lower doping concentration, (3) EDF has narrower gain bandwidth. Nevertheless, the longer lasing wavelength of EDF lasers is attractive in telecommunications, in vivo three-photon microscopy [2], and mid-infrared pulse generation [3]. The highest energy of sub-picosecond pulse from similariton or dissipative soliton EDF oscillators was 20 nJ (750 fs, 1.2 W pump) [4], where a short (59 cm) EDF and long (57 m) passive fibers were used to suppress the nonlinear chirp via strong normal dispersion. However, the grating-pair-compressed pulse still exhibited a highly oscillating tail with poor (56%) compression efficiency (defined as the energy in the temporal main lobe over the total energy) [5].Previously we demonstrated a mode-locked fiber oscillator consisting of small-core EDF and an intracavity pulse shaper, producing 268 fs, 8.9 nJ pulse with 67% compression efficiency at 320 mW pump power [6]. The nonlinear chirp could be suppressed by adding spectral phase modulation via the pulse shaper without incurring extra dispersion. In this work, we report improvements on the pulse width (191 fs), pulse energy (31 nJ), and compression efficiency (90%) by a new cavity design and increased pump power (720 mW). The 31 nJ pulse energy is 1.6-fold of the previous record, while achieved at 60% of the pump power. The output spectrum could be manipulated by controlling the polarization and spectral filtering elements to support 86 fs (FWHM) transformlimited (TL) pulse at lower (21 nJ) energy.