We compare different pulse durations, modes and repetition rates of infrared ultrashort pulses lasers for the inscription of printed electronics sensors under 100 μm scale. We investigate pulse widths varying from 200 fs up to 10 ps, and standard single pulse versus 5 GHz burst regimes to produce the most efficient and cleanest ablation. The aim of the investigated process is to ablate a layer of conductive material like carbon, NiAl or NiCr forming the electronic track contours, without damaging the support which is made of a dielectric insulator. Depending on the materials and substrates of the printed electronics circuits, we have observed that 10 ps pulses in GHz burst regime with moderate individual pulse energy (around 10 μJ) have a lot of potential for an efficient production.
Frequency-Shifted-Feedback Mode-Locked Fibre Lasers are not as common as SESAM-based or figure 8/9 mode-locked ultrafast fiber lasers. It is mainly because that type of lasers requires a frequency-shifter like Acousto-Optics Modulator (AOM) which increases the complexity of the system for similar operation. Here, we took benefit of the optical transmission modulation and wavelength shifting effects of the AOM to build a fiber laser that can operate at different repetition rates. Pulsed operation (100ps) at the fundamental repetition rate (3.5MHz) of the laser cavity as well as first and second harmonics regimes have been obtained and show stable behaviour over hours.
We propose here to study experimentally and numerically periodic amplitude fluctuations of a pulse train emitted by a 1030 nm all-PM fiber mode-locked laser. Nonlinear Polarization Evolution (NPE) permits to achieve the mode-locking operation. NPE only occurs along a long span of standard PM fiber located between an off-axis polarizer and a Faraday Mirror. In the rest of the cavity composed of an Ytterbium doped fiber and a chirped Fiber Bragg Grating, NPE does not occur because the light propagates only according to the slow axis of the fiber. When the mode-lock regime is established, the laser delivers a stable pulse train at a repetition rate of 1.01 MHz. Beyond a given pump power, a periodic amplitude fluctuation of the pulse train appears. This fluctuation has a period two times longer than the pulse train period: a pulse with high amplitude is always followed at the next round-trip by a pulse with smaller amplitude and this latter is followed by a high amplitude pulse and so on. It forms a so-called period doubling. The amplitude modulation increases with the pump power. If the pump power is further increased, then period quadrupling and then octupling are observed and an experimental bifurcation diagram is reported. A significant increasing of pump power leads to a route to chaotic amplitude variation.
We report on an on-field CO2 sensing experiment based on a rapidly modulated optical parametric oscillator (OPO). This OPO is pumped by a mode-locked fibre laser source delivering 120 ps pulse laser with a spectral width of about 0.03 nm at a repetition frequency of 40 MHz and an average power of 5W. The output wavelength of the fibre laser pump source can be rapidly modulated resulting in a modulated mid-IR signal. This modulated signal around 2.7 μm was used for CO2 detection during a field experiment by a deported (~100m) sampling method.
We report a full experimental comparison study on the injection of a Ti:Sa multi-TW amplifier chain with a standard 15 fs Ti:Sa oscillator and a 35 fs frequency doubled fiber oscillator. The study highlights that the Ti:Sa oscillator with high performances in term of pulse duration and spectral width can be replaced by the frequency doubled fiber oscillator to seed Ti:Sa amplifier chains without almost any compromise on the output pulse duration and the picosecond contrast. Finally, we demonstrate for the first time of our knowledge a 30 TW and 33 fs Ti:Sa amplifier injected by a fiber oscillator.
Nowadays, the request for femtosecond lasers operating between 1.7 μm and 2 μm is continuously growing for many applications. Mode-locked Holmium- or Thulium-doped fiber lasers based on Saturable Absorber Mirror (SAM) are typically the first approach to generate pulses in this spectral range but this technique suffers from a lack of tunability. Indeed, the operating wavelength is fixed by the SAM and the gain fiber. Another way to reach the 2 μm-spectral range consists to exploit the nonlinear phenomena appearing in optical fibers and in particular the Soliton-Self Frequency Shift (SSFS) effect from an Erbium-fiber laser. Several systems based on this phenomenon allowed the generation of ultrashort pulses at different wavelengths and in different type of fibers (step-index, PCF, …). In this paper, we report on the design of a compact and robust all-Polarization-Maintaining (PM) fiber system entirely based on commercial PM components. This system allows to generate a single femtosecond pulse continuously tunable from 1700 nm to 2050 nm. We also demonstrate that the sub-150 fs pulses are transform-limited over all the spectral range and thanks to an optimized rate conversion close to 50 %, the pulse energy and the peak power can reach the nJclass and the kW-class respectively, which represents a gain a of factor 2 compared to the previous works.
Nowadays, the request for femtosecond lasers operating between 1.7 μm and 2 μm is continuously growing for many applications. Mode-locked Holmium- or Thulium-doped fiber lasers based on Saturable Absorber Mirror (SAM) are typically the first approach to generate pulses in this spectral range but this technique suffers from a lack of tunability. Indeed, the operating wavelength is fixed by the SAM and the gain fiber. Another way to reach the 2 μm-spectral range consists to exploit the nonlinear phenomena appearing in optical fibers and in particular the Soliton-Self Frequency Shift (SSFS) effect from an Erbium-fiber laser. Several systems based on this phenomenon allowed the generation of ultrashort pulses at different wavelengths and in different type of fibers (step-index, PCF, …). In this paper, we report on the design of a compact and robust all-Polarization-Maintaining (PM) fiber system entirely based on commercial PM components. This system allows to generate a single femtosecond pulse continuously tunable from 1700 nm to 2050 nm. We also demonstrate that the sub-150 fs pulses are transform-limited over all the spectral range and thanks to an optimized rate conversion close to 50 %, the pulse energy and the peak power can reach the nJclass and the kW-class respectively, which represents a gain of a factor 2 compared to the previous works.
KEYWORDS: Microscopes, Second-harmonic generation, Fiber lasers, Luminescence, Signal detection, Skin, In vivo imaging, Microscopy, Optical amplifiers, Laser development
We demonstrate the use of an all-PM fiber laser, delivering 35 fs pulses at 800 nm and a 40-MHz repetition rate, for twophoton excited fluorescence (2PEF) and Second Harmonic Generation (SHG) nonlinear microscopy. The laser has been combined to a compact group delay dispersion pre-compensation set-up to ensure the shortest pulse and so the highest peak power on the sample, minimizing the risk to damage it. We carried out measurements on vegetal samples like vine shoot or cleaning paper as well as on the forefinger of a volunteer, for current biocompatible powers under 10 mW. To the best of our knowledge, the use of an all-PM fiber laser delivering 35 fs pulses for microscopy applications has never been reported. Due to its compactness and cost-efficiency, this laser is a very attractive alternative to Ti:Sapphire modelocked lasers.
Frequency doubled sub 50 fs Erbium-fiber lasers are ideal tool used to seed Ti:sapphire amplifier. Therefore, over last decade large number of all-fiber laser architecture has been reported for such application. Nevertheless, the emitted pulses are usually too long due to the gain bandwidth of Erbium or the laser architecture is not made with Polarization Maintaining (PM) fibers which will be a limitation for frequency doubling. We demonstrate a new design of an all-PM erbium doped fiber laser emitting sub 50 fs pulses with high pulse energy and we study its frequency doubling. Our architecture is based on a concatenation of three amplifiers having different group velocity dispersion. These amplifiers provide numerous degrees of freedom allowing to control the output pulse duration. Thanks to this new design, the laser produces 14 nJ pulse with a duration of 48 fs and an average power of 560 mW. This is to the best of our knowledge the shortest pulse duration with an energy higher than 10 nJ emitted by an all-fiber laser around 1.5-1.6 μm. The pulses are further converted by Second Harmonic Generation to 796 nm with an efficiency of 25 %. The average power of the doubled signal is 140 mW with 3.5 nJ pulse energy. The nonlinear crystal has been carefully chosen in order to cover all the spectral bandwidth of the pump and to ensure a sub 50 fs pulse at 796 nm.
ALPhANOV has developed expertise around the interfacing and integration of specialty optical fibers. We propose to present new developments concerning 100W-class fiber laser based on Yb-doped Large Mode Area fiber amplifier and a new plug-and-play connector for ultrashort pulse beam delivery by using Hollow Core Photonic Crystal Fibers.
In terms of high power fiber amplifier, we recently developed a high performance, fully monolithic PCF amplifier module. The module is based on the DC-200/40-PZ-Yb of NKT Photonics and on a homemade fiber fused component allowing us to couple up to 6 pumps of 50 W at 976 nm together with 5 W of signal, leading to an achieved power of 210 W at 1064 nm, which is to the best of our knowledge the highest power ever delivered by a fully monolithic PCF amplifier. The module is entirely thermally controlled in a rugged package and has run more than 100 days at > 100W average power with an excellent power stability < 1%.
Concerning fiber beam delivery solution, hollow core photonic crystal fiber has shown great potential for an industrial solution. To penetrate the industry, high power femtosecond lasers need low-loss stable and plug-and-play connectors to couple light into hollow-core single-mode fibers and carry it to the target. We recently developed such connector and tested it on different industrial femtosecond laser, 50W and 100W class. The new design of the connector compatible with vacuum or noble gas and 300W class femtosecond laser will also be presented.
We report on an hybrid fiber/crystal ultra-short pulsed laser delivering high pulse energy and high peak power in the picosecond regime. The laser is composed of a mode-lock fiber oscillator, a pulse picker and subsequent fiber amplifiers. The last stage of the laser is a single pass Nd:YVO4 solid-state amplifier. We believe that this combination of both technologies is a very promising approach for making efficient, compact and low cost lasers compatible with industrial requirements.
In this study, a polarization maintaining (PM) all-fiber laser oscillator passively mode locked at 1.03 μm is presented. The mode locking is achieved by nonlinear polarization evolution occurring along a long span of standard PM fiber (26 m) spliced between an off-axis polarizer and a Faraday rotator mirror. The influence of the total chromatic dispersion and intra-cavity spectral filtering on pulsed operation is studied. Two experimental configurations have been tested. The first configuration is an all normal dispersion cavity using a looped fibered circulator combined to a 1.5 nm filter used as an end cavity mirror. The second configuration used highly reflective chirped Fiber Bragg Grating (FBG) exhibiting different bandwidths (0.7 nm, 1.1 nm and 1.83 nm). The chromatic dispersion induced is +7.2 ps/nm for each FBG. Stable single-pulse mode locked operation has been demonstrated for each configuration. The study highlights however different mode-locking operations according to the intra-cavity spectral filtering and total chromatic dispersion of the cavity. For the first configuration, pulse duration is about 7 ps. According to the optical spectrum which has a FWHM of 2.2 nm, pulses may be compressed to subpicosecond durations with the help of a suited compressor like bulk gratings. Shortest pulses of 2.2 ps have been obtained at a repetition rate of 3.3 MHz with the second experimental configuration. To our knowledge, this is the smallest pulse duration delivered by a fully fibered mode locked laser operating at a repetition rate lower than 10 MHz without any external pulse compressor.
We present in this study a PM all-fiber laser oscillator passively mode-locked (ML) at 1.03 μm. The laser is based on
Nonlinear Polarization Evolution (NPE) in polarization maintaining (PM) fibers. In order to obtain the mode-locking
regime, a nonlinear reflective mirror including a fibered polarizer, a long fiber span and a fibered Faraday mirror (FM) is
inserted in a Fabry-Perot laser cavity.
In this work we explain the principles of operation of this original laser design that permits to generate ultrashort pulses
at low repetition (lower that 1MHz) rate with a cavity length of 100 m of fiber. In this experiment, the measured pulse
duration is about 6 ps. To our knowledge this is the first all-PM mode-locked laser based on the NPE with a cavity of
100m length fiber and a delivered pulse duration of few picosecondes.
Furthermore, the different mode-locked regimes of the laser, i.e. multi-pulse, noise-like mode-locked and single pulse,
are presented together with the ways of controlling the apparition of these regimes. When the single pulse mode-locking
regime is achieved, the laser delivers linearly polarized pulses in a very stable way.
Finally, this study includes numerical results which are obtained with the resolution of the NonLinear Schrodinger
Equations (NLSE) with the Split-Step Fourier (SSF) algorithm. This modeling has led to the understanding of the
different modes of operation of the laser. In particular, the influence of the peak power on the reflection of the nonlinear
mirror and its operation are studied.
We present a theoretical and experimental study on PM ultra-short fiber laser cavities operating at low repetition rate.
The mode-locking operation in this study always relies on SEmicondutor Saturable Absorber Mirror (SESAM) and intracavity
spectral filtering. Several experimental configurations have been tested and modeled. Repetition rates as low as
7.7 MHz with sub-picosecond pulse duration have been obtained. A longer cavity has also been modeled in order to
determine if stable ultra-short pulsed operation would also possible at lower repetition rates.
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