We present an all-fiber integrated master oscillator power amplifier operating at 1940 nm. The source delivers 422-nJ chirped pulses at a repetition rate of 10.18 MHz corresponding to 4.3 W of average power. The pulses were recompressed down to 900 fs yielding 220 kW of peak power. Stretching the pulse to 200 ps allows further energy scaling beyond the microjoule barrier at low repetition rate (Ep = 4 μJ at 92 kHz, Δτp =1.6 ps).
New wavelengths of laser radiation are of interest for material processing. Results of application of the all-fiber ultrashort pulsed laser emitting in 2 µm range, manufactured by Novae, are presented. Average output power was 4.35 W in a single-spatial-mode beam centered at the 1950 nm wavelength. Pulses duration was 40 ps, and laser operated at 4.2 MHz pulse repetition rate. This performance corresponded to 25 kW of pulse peak power and almost 1 µJ in pulse energy. Material processing was performed using three different focusing lenses (100, 30 and 18 mm) and mechanical stages for the workpiece translation. 2 µm laser radiation is strongly absorbed by some polymers. Swelling of PMMA surface was observed for scanning speed above 5 mm/s using the average power of 3.45 W focused with the 30 mm lens. When scanning speed was reduced below 4 mm/s, ablation of PMMA took place. The swelling of PMMA is a consequence of its melting due to absorbed laser power. Therefore, experiments on butt welding of PMMA and overlapping welding of PMMA with other polymers were performed. Stable joint was achieved for the butt welding of two PMMA blocks with thickness of 5 mm. The laser was used to cut a Kapton film on a paper carrier with the same set-up as previous. The cut width depended on the cutting speed and focusing optics. A perfect cut with a width of 11 µm was achieved at the translation speed of 60 mm/s.
We report on the generation of femtosecond pulses from an all-normal-dispersion fiber laser featuring a large-mode-area
ytterbium-doped photonic-crystal fiber. Nonlinear polarization evolution assisted by passive spectral filtering in
combination with the large-pitch fiber design enables a significant peak power enhancement with the generation of
multi-megawatt pulses. 65 W of average power at 76.5 MHz repetition rate, corresponding to 850 nJ pulses are generated
in a compact oscillator setup. The output pulses are extra-cavity dechirped down to 111fs with 6 MW of peak power. To
the best of our knowledge, these are the highest average and peak powers ever reached by a mode-locked fiber laser.
We report on generation of high-energy pulses in a highly-normal dispersion fiber laser featuring large-mode-area
microstructure fibers. Passive mode-locking is achieved using high modulation depth semiconductor saturable
absorber mirror (SESAM). The total cavity dispersion is varied through insertion of a low-nonlinearity passive
microstructure fiber inside the cavity. We study the effect of the cavity dispersion on the mode-locking performances.
A systematic experimental and numerical description of the laser operation is addressed and the impact
of the spectral filtering on the laser performances is discussed.
We report on the generation of microjoule level picosecond pulses from a mode-locked Yb-doped LMA fiber laser
operating in the purely normal dispersion regime. The self-starting oscillator stabilized with slow relaxation
semiconductor saturable absorber (SAM) emits 11 W of average power at a pulse repetition rate of 10 MHz,
corresponding to a pulse energy of 1.1 μJ. The laser produces a 0.4 nm narrow emission line with 310 ps output pulses.
In the femtosecond operation, the oscillator stabilized with fast relaxation SAM emits 9 W of average power at a pulse
repetition rate of 9.7 MHz, corresponding to a pulse energy of 927 nJ. The laser produces positively chirped output
pulses of 8 ps which are compressed down to 711 fs, corresponding to megawatt peak power. To our knowledge this is
the first time that mode-locked fiber oscillators can generate higher pulse energies of beyond microjoule-level at high
average output power.
We report on an all-normal dispersion passively mode-locked fiber laser based on an ytterbium-doped largemode-
area microstructure fiber and featuring high-energy ultra-short pulses. Mode-locking was achieved with a
high modulation depth semiconductor saturable absorber mirror (SESAM). We investigate the influence of the
modulation depth of the SESAM on the laser performances. We show that mode-locking could be achieved with
a modulation of only 10 %. However, the best performances in term of pulse energy are obtained with the highest
modulation depth (35 %). In this case, the laser delivers 3.3 W average output power with positively-chirped 5.5
ps pulses at a center wavelength of 1033 nm. The pulse repetition rate is 46.4 MHz, which results in an energy
per pulse of 71 nJ. These pulses are extra-cavity de-chirped down to 516 fs using bulk gratings. The average
power of the de-chirped pulses is 2.3 W, which corresponds to a peak power of more than 96 kW.
We report on the generation of 265 nJ ultra-short pulses from a mode-locked Ytterbium-doped short-length large-mode-area
fiber laser operating in the dispersion compensation free regime. The self-starting oscillator emits 2.7 W of average
power at a pulse repetition rate of 10.18 MHz. The pulses have been compressed down to 400 fs, corresponding to 500
kW peak power. Numerical simulations confirm the stable solution and reveal the mechanisms for self-consistent intra-cavity
pulse evolution. The pulse energy is one order of magnitude higher than so far reported for fiber oscillators in the
1 μm wavelength region. To our knowledge this is the first time that mode-locked fiber oscillators can compete in terms
of pulse energy and peak power with most advanced bulk solid-state femtosecond lasers.
We report on a all-normal dispersion mode-locked fiber laser based on a large-mode-area ytterbium-doped microstructure fiber and using a high nonlinear modulation depth semiconductor saturable absorber mirror (SESAM). The laser delivers 3.3 W average output power with positively-chirped 5.5 ps pulses at a center wavelength of 1033 nm. The pulse repetition rate is 46.4 MHz, which results in an energy per pulse of 71 nJ. These pulses are extra-cavity de-chirped down to 516 fs using bulk gratings. The average power of the de-chirped pulses is 2.3 W, which corresponds to a peak power of more than 96 kW.
We report, to the first time to our knowledge, on a passively mode-locked single-polarization single-transverse-mode
large-mode-area photonic crystal fiber laser operating in the dispersion compensation free regime. In the single-pulse
regime, the laser generates 1.6 W of average power with 3.7 ps pulses at a repetition rate of 63 MHz, corresponding to a
pulse energy of 25 nJ. Stable and self-starting operation is obtained by adapting the spot size at the saturable absorber
mirror to the pulse evolution in the low-nonlinearity fiber. The pulses are compressible down to 750 fs. The presented
approach demonstrates the scaling potential of fiber based short pulse oscillators towards high-power ultra-compact allfiber
We report on the generation of self-similar highly-stable femtosecond pulses from a side-pumped ytterbium-doped double-clad fiber laser. Positively-chirped parabolic pulses with 6.4 ps duration and more than 3.2 nJ energy are obtained. These pulses are extra-cavity compressed to 140 fs. The noise measurements using radio-frequency analysis show that this regime of emission ensures low-noise operation with less than 0.05 % amplitude fluctuations.
We report passive harmonic mode locking of a high-power Yb-doped double-clad fiber laser operating in both the normal- and the anomalous-dispersion regimes with a fundamental repetition rate of 20.4 MHz. In the anomalous-dispersion regime (total cavity GVD of -0.1 ps2), 1-ps, 125-pJ pulses are emitted at a repetition rate of 408 MHz. When the total net dispersion is close to zero (about -0.004 ps2), 680 fs, 48 pJ pulses are emitted at a repetition rate higher than 2 GHz. The supermodes suppression is than about 25 dB. In the normal-dispersion regime (total cavity GVD of +0.047 ps2), 116-fs, 1.7-nJ pulses are emitted at a repetition rate of 102 MHz with a supermodes suppression of more than 60 dB. We also report a new regime of multiple pulsing emission observed with this fiber laser : the stable emission of two pairs of bound pulses exhibiting different time separations and uniformly separated in the same cavity round trip.
Keywords: Harmonic mode locking, multiple pulsing, bound states.
We consider an Yb-doped double-clad fiber laser in a unidirectional ring cavity containing a polarizer placed between two half-wave plates. Depending on the orientation of the phase plates, the laser operates in continuous, Q-switch, mode-lock or unstable self-pulsing regime. An experimental study of the stability of the mode locking regime is realized versus the orientation of the half-wave plates. A model for the stability of self-mode locking and cw operation is developed. The model is reduced to a master equation in which the coefficients are explicitly dependent on the orientation angles of the phase plates.
We present an experimental study of the Yb-doped double-clad fiber laser operating in the 1.08 micrometers wavelength. The fiber side-pumped with a high power laser diode using the v- groove technique. Various experimental configurations are performed from the linear cavity to an all-fiber tunable unidirectional ring cavity. Mode-locking of the Yb laser are investigated using the nonlinear polarization rotation.
We theoretically model the polarization properties of an optical fiber by the Jones matrix of an elliptical birefringent plate. The properties of this model are investigated and lead to develop experimental methods to extract the parameters of the model for a real fiber. A magneto-optical method that measures the beat length of the fiber is also presented and gives a more complete description of the fiber. Wavelength dependence of the parameters characterizing the fiber is finally experimentally investigated.
We present an experimental study of the Yb-doped double-clad fiber laser operating in the 1.08 micrometers wavelength. The fiber is side-pumped with a high power laser diode using the v-groove technique. Various experimental configurations are performed from the linear cavity to an all-fiber tunable unidirectional ring cavity.