Miniaturized optofluidic platforms play an important role in bio-analysis, detection and diagnostic applications. The advantages of such miniaturized devices are extremely low sample requirement, low cost development and rapid analysis capabilities. Fused silica is advantageous for optofluidic systems due to properties such as being chemically inert, mechanically stable, and optically transparent to a wide spectrum of light. As a three dimensional manufacturing method, femtosecond laser scanning followed by chemical etching shows great potential to fabricate glass based optofluidic chips. In this study, we demonstrate fabrication of all-fiber based, optofluidic flow cytometer in fused silica glass by femtosecond laser machining. 3D particle focusing was achieved through a straightforward planar chip design with two separately fabricated fused silica glass slides thermally bonded together. Bioparticles in a fluid stream encounter with optical interrogation region specifically designed to allocate 405nm single mode fiber laser source and two multi-mode collection fibers for forward scattering (FSC) and side scattering (SSC) signals detection. Detected signal data collected with oscilloscope and post processed with MATLAB script file. We were able to count number of events over 4000events/sec, and achieve size distribution for 5.95μm monodisperse polystyrene beads using FSC and SSC signals. Our platform shows promise for optical and fluidic miniaturization of flow cytometry systems.
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 demonstrate a femtosecond fiber laser system delivering >5-μJ, sub-400-fs pulses at a pulse repetition rate of
200 kHz. At constant average power the pulse repetition rate of this Watt-level femtosecond laser can be adjusted up to
several MHz. The laser is monolithically integrated from the oscillator to the booster amplifier stage. The system was
applied for structuring metallic as well as transparent media as e.g. biological tissues in ophthalmology.
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.
In this contribution, we report on spectral combination of four sub-5ns pulsed fiber amplifier systems with an average
output power of 200W at 200kHz repetition rate resulting in 1mJ of pulse energy. A dielectric reflection grating is used
to combine four individual beams to one output possessing a measured M<sup>2</sup> value of 1.3 and 1.8, respectively,
independent of power level. Extraction of higher pulse energies and peak powers will be discussed.
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 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 on experimental generation of wave-breaking-free pulses from an environmentally stable Yb-doped all-fiber
laser. The compact linear cavity is constructed with saturable absorber mirror directly glued to the fibers end-facet as
nonlinear mode-locking mechanism and chirped fiber Bragg grating (CFBG) for dispersion management, thus, without
any free-space optics. Further, the laser was intrinsically environmentally stable, as only polarization maintaining (PM)
fibers were used. In the wave-breaking-free regime, the fiber laser directly generates positively-chirped picosecond
pulses at a repetition rate of 20.30 MHz. These pulses can be compressed to 218 fs in a HC-PBG providing a
femtosecond all-fiber laser system. Adapting the intra cavity dispersion we have also generated chirped pulses with a
parabolic spectral profile in the stretched pulse regime. We confirm numerically the wave-breaking-free pulse and
stretched pulse evolution and discuss advantages and disadvantages of both regimes in terms of pulse quality.
We show spectral combination of pulsed fiber laser systems for the first time to our knowledge. In this proof of principle
experiment, two directly modulated wavelength-stabilized tunable external cavity diode lasers (ECDL) serve as
independent seed sources. Each signal is amplified in a two stage ytterbium-doped fiber amplifier. The spatial overlap is
created using a transmission grating with a combining efficiency as high as 92 %. No beam quality degradation has been
observed for the combined beam compared to a single emission. An electronic delay is used to adjust the temporal
overlap of the pulses from the spatially separated amplifier setups. The presented approach offers an enormous scaling
potential of pulsed fiber laser systems, which are generally limited by nonlinear effects or fiber damage. We show that
the huge gain bandwidth of Yb-doped fiber amplifiers and the high diffraction efficiency of dielectric reflection gratings
in this wavelength range yield potential for a combination of up to 50 channels. For state-of-the-art ns-amplifier systems
> 100 MW of peak power, > 100 mJ of pulse energy and average powers of > 10 kW seem feasible.
We report on a high repetition rate noncollinear optical parametric amplifier system (NOPA) seeded by a cavity
dumped Ti:Sapphire oscillator. The pump pulses for parametric amplification are generated via soliton generation in a
highly nonlinear photonic crystal fiber with a subsequent fiber-based amplification stage and are therefore
synchronized. The system is capable of producing high energy ultra-short pulses at repetition rates up to 2 MHz.
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, 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 a high power, high-energy femtosecond fiber source based on direct amplification of parabolic pulses from an environmental stable passively mode-locked fiber oscillator in an Yb-doped single-polarization photonic crystal fiber. The system delivers a pulse energy of 1.2 μJ (21 W average power) at a repetition rate of 17 MHz and a pulse duration of 240 fs in a linearly polarized beam with diffraction-limited quality. The special pulse shape allows for the generation of high quality femtosecond pulses beyond nonlinearity limits, which is confirmed by numerical simulations.
We report on the observation of both single pulse and bound states of an environmentally stable all-polarization maintaining (PM) mode-locked laser based on a saturable absorber. The laser operates in the self-similar regime, and parabolic pulse spectra were obtained. The pulses could externally be compressed to 212 fs (single pulse) and 248 fs (bound states). Results of a numerical model are also presented. The model reveals important information about the criteria for obtaining pulses with parabolic temporal shape.
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 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.