In this communication, we report for the first time on a homemade 55 µm core VLMA “Yb-free” Er-doped aluminosilicate double-clad fiber manufactured by the REPUSIL powder sintering technology and its implementation within two different laser configurations emitting around 1560 nm, both pumped at 976 nm. First, a free-running free-space CW oscillator delivers up to 40 W of average power with optical-to-optical efficiency of 30 % and near-diffraction-limited beam, despite the large core size. In a second experiment, the fiber is used as the main amplifier of a MOPA system delivering up to 10 nJ pulses at GHz repetition rate.
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.
A single-frequency blue laser at 461 nm is generated by frequency doubling an amplified diode laser operating at 922 nm via a LBO crystal placed in an ultra-compact resonant linear cavity. The best optical conversion efficiency achieved by the setup is 87% which gives more than 1 W of power in the blue. The frequency-converted beam is characterized in terms of long-term power stability, residual intensity noise, hysteresis induced by the input power stability, and geometrical shape. The generated 461 nm radiation can be used to obtain a magneto-optical trap on strontium 5s21S0 – 5p1 P1 transition.
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.
Over the last decade, frequency comb spectroscopy have led to significant developments in view of the identification of varied species and of the understanding of the structure of matter.
Highly efficient amplification of frequency comb femtosecond oscillators in the high pulse energies regime should allow future applications using this approach to Lidar-type measurements.
We report on the millijoule level design of femtosecond amplifiers near 2 μm wavelength having a great optical efficiency and compactness in order to be carrier in satellites. In addition to space applications, laser systems at 2 μm become more and more popular because they offer elegant solutions to generate ultra-broad band super-continuum in the mid-infrared and for material processing.
Our study helps to compare the optical performance of Tm:YAG, Tm:YAP and Tm:YLF crystals as active media, for designing ultrashort pulse regenerative amplifiers with a high gain and wall-plug efficiencies up to 10%. We will present our approach to ensure the conservation of the initial phase shift between the envelope and the carrier of pulses during amplification.
We primarily discuss an innovative model which proposes a gradual path towards the optimization of any regenerative amplifier using crystalline thulium-based, end-pumped doped rods. This also involves the analysis of sizing criteria based on the assumption of rod-based active media, including the doping content, the length of the rod and the beam size inside.
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.
We report on a 3 W Mid-IR supercontinuum extended up to 4.6 μm based on an all-PM thulium doped fiber gainswitched laser seeding an InF3 fiber. This innovative fiber presents a specific design that increases non-linear effects and shows very weak background losses. Thanks to the versatility of our gain-switched laser, all the pulse parameters have been widely optimized to generate a supercontinuum emission with the highest average power and the largest spectrum.
LMJ is typical of lasers used for inertial confinement fusion and requires a laser of programmable parameters for
injection into the main amplifier. For several years, the CEA has developed front end fiber sources, based on
telecommunications fiber optics technologies. These sources meet the needs but as the technology evolves we can expect
improved efficiency and reductions in size and cost.
We give an up-to-date description of some present development issues, particularly in the field of temporal shaping with
the use of digital system. The synchronization of such electronics has been challenging however we now obtain system
jitter of less then 7ps rms.
Secondly, we will present recent advance in the use of fiber based pre-comp system to avoid parasitic amplitude
modulation from phase modulation used for spectral broadening.
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