Sub-80 fs dissipative soliton large-mode-area fiber laser

Abstract

We report on high-energy ultrashort pulse generation from an all-normal-dispersion large-mode-area fiber laser by exploiting an efficient combination of nonlinear polarization evolution (NPE) and a semiconductor-based saturable absorber mode-locking mechanism. The watt-level laser directly emits chirped pulses with a duration of 1 ps and 163 nJ of pulse energy. These can be compressed to 77 fs, generating megawatt-level peak power. Intracavity dynamics are discussed by numerical simulation, and the intracavity pulse evolution reveals that NPE plays a key role in pulse shaping. © 2010 Optical Society of America OCIS codes: 060.2310, 060.2320 High-performance laser sources delivering ultrashort pulses with energies at the hundred nanojoule level or beyond will open up new directions for ultrafast scientific and industrial applications, ranging from highprecision laser structuring of various micro-/nanotargets to nonlinear optics. Rare-earth-doped fiber lasers present unique properties due to diffractionless propagation and the absence of thermo-optical problems. Because of the light confinement, fiber lasers offer a remarkable opportunity to develop highly stable laser sources, making them ideal candidates for real-world applications. The development of mode-locked fiber lasers operating in the normal dispersion regime to achieve higher pulse energies has been demonstrated [1,2]. Such lasers support dissipative solitons [3] and could produce sub-100 fs pulses with energies as high as 30 nJ using standard single-mode fibers [4]. More recently, exceptional performances in terms of pulse energy and peak power have been demonstrated in mode-locked fiber lasers using large-mode-area (LMA) photonic crystal fibers [5][6][7][8][9]. However, these lasers operate at a low accumulated nonlinear phase and produce relatively long pulses >300 fs. The generation of ultrashort pulses in a dissipativesoliton laser strongly relies on the amount of nonlinearity accumulated along the cavity, which should be enough to ensure sufficient spectral broadening. However, generation of ultrashort pulses with broad bandwidths in an allnormal-dispersion laser needs a strong pulse-shaping mechanism to prevent excessive temporal expansion. One solution is the use of a narrow spectral filter to achieve self-consistent evolution inside the laser cavity [4]. Indeed, spectral filtering of a chirped pulse produces a strong amplitude modulation in the time domain, which increases with spectral breathing. Recently, the generation of sub-150 fs pulses with 24 nm spectral width has been demonstrated in an Yb-doped LMA fiber laser using a saturable absorber mirror (SAM) [10].In this Letter we report the generation of sub-80 fs pulses from a passively mode-locked all-normaldispersion laser featuring an LMA photonic crystal fiber. By exploiting the combined action of an SAM and nonlinear polarization evolution (NPE) for pulse shaping, the laser directly generates 1 ps chirped pulses with pulse energies above 160 nJ at watt-level average power. These pulses...

High-energy femtosecond photonic crystal fiber laser

“…Moreover, the employment of low-nonlinearity large-mode-area photonic crystal fibers (PCFs) enables significant power scaling. This has been demonstrated recently in ANDF laser configurations using different pulse shaping mechanisms [9][10][11][12][13][14]. Notably, the extension of this approach to photonic crystal rods has produced subpicosecond (700 fs) pulses with microjoule energy levels [14].…”

“…Suggesting that the NPE mechanism plays a key role in pulse shaping, an ideal saturable absorber with monotonically increasing transmission is introduced just after the gain fiber [7,15]. Absorption of the SAM is described by the rate equation model with a relaxation time of 500 fs [13]. To consider the finite bandwidth of the resonant SAM, a passive SF with 20 nm width is introduced in the numerical model.…”

Ultrashort pulse formation and evolution in mode-locked fiber lasers

“…The increased mode area decreases the intensity of the light field, additionally the interaction length can be significantly reduced by reducing the fiber section in the cavity to the extreme case of solely a short piece of gain fiber. Exploiting the advantages of microstructured fibers together with high-energy dissipative soliton pulse shaping a tremendous performance increase in terms of pulse energy, peak power and also average power has been obtained [26][27][28][29].…”

Sub-picosecond microjoule-class fiber lasers

“…Consequently, the employment of low-nonlinearity large-mode-area photonic crystal fibers (PCF) enables significant power scaling. Fiber oscillators that reach the megawatt peak powers have been reported based on this approach [4][5]. Notably, the extension of this approach to photonic crystal rods opens the road for sub-picosecond microjoule-class fiber sources [6][7].…”