Sylvain Bordais

1 kW peak power, 110 ns single-frequency thulium doped fiber amplifier at 2050 nm

We report a high power, single frequency, linearly polarized master oscillator power amplifier emitting 110 ns, 1 kW peak power pulses at 2050 nm. A 20% slope efficiency and a beam quality of M2=1.21 are achieved with three-stage double-clad Tm(3+)-doped fiber architecture. Various pump schemes are compared leading to the conclusion that 793 nm pump wavelength is the most efficient for amplification at 2050 nm. Based on numerical simulations, the Brillouin gain coefficient around 2 μm in Tm(3+) highly doped silica fiber is estimated to 1.2×10(-11) m/W. Output peak power is limited by stimulated Brillouin scattering to 535 W without mitigation and to 1 kW with application of a strain distribution along the doped fiber.

Double-clad 10-W Yb 3+ -doped fiber master oscillator power fiber amplifier for He 3+ optical pumping

We describe an all-fiber ytterbium-doped laser followed by a double-stage ytterbium-doped double-clad fiber amplifier of 10-W output power for helium pumping. Different cavity designs are investigated with the goal of achieving high-power multimode emission at 1083 nm, wavelength tunability over the helium absorption bands, and linewidth envelope control over the range 1-3 GHz. We point out the domains with unstable output power and discuss their origin.

Fiber composition influence on spontaneous Brillouin scattering properties in double-clad fiber amplifiers

Brillouin properties of doped fibers are reported for the first time. The characterized fibers present Brillouin frequency shift variation that we attribute to fiber composition. A thermally induced evolution of Brillouin spectrum has been observed.

High power cladding-pumped Er3+/Yb3+ fiber amplifiers: technologies, performances and impact of nonlinear effects

Yb3+-sensitized Er3+-doped fibers are attracting increasing interest because of the high achievable performances, such as high gain and pump efficiency. High output power can be obtained from a double clad (dc) Er3+/Yb3+ co-doped fiber pumped with broad area high power pump laser diodes. The principle of amplification in this kind of co-doped fibers is presented in this paper. Different solutions for the injection of pump power in the 1st-cladding have been described. The energy transfer mechanism in a Er3+/Yb3+ co-doped system including cooperative-upconversion process is explained. Gain and absorption properties ofdc fibers have been determined experimentally and inserted in a theoretical amplifier model. Good agreement between measurements and modelling has been obtained. Hybrid Er3+-Er3+/Yb3+ amplifier architectures are suitable to obtain + 30 dBm output power. The gain bandwidth is in the 1535–1565 nm range for single wavelength operation. A spectral gain flatness is observed in a reduced C-bandWDM operation (i.e. 1545–1565 nm) without gain-flattening filter. Nonlinear effects such as the optical Kerr effect or the stimulated Brillouin scattering can be observed in high power amplifiers due to the high output peak power confined in the fiber core. These two nonlinear phenomena have been investigated for different high power amplifier configurations. Numerical modelling have also confirmed the observed signal distortions.RésuméLes fibres co-dopées Er3+/Yb3+ présentent un grand intérêt car des gains élevés et de grandes efficacités de pompage peuvent être obtenus. Une puissance de sortie élevée est possible avec une fibre co-dopée Er3+/Yb3+ à double gaine pompée par une diode de puissance de large surface d’émission. Différentes techniques d’injection de la puissance de pompe dans la 1ère gaine sont décrites. Le mécanisme de transfert d’énergie dans un système Er3+/Yb3+, qui prend en compte le phénomène de recombinaison par états excités, est présenté. Les mesures du gain et d’absorption dans la fibre ont permis de développer un modèle de simulation pour un amplificateur Er3+/Yb3+. Une bonne concordance entre mesures et modélisation a été observée. Des architectures d’amplificateur hybrides Er3+-Er3+/Yb3+ sont préférables pour l’amplification d’une seule longueur d’onde. Une platitude de gain en bande C réduite (1545–1565 nm) est observée en régimeWDM sans l’utilisation d’un filtre égaliseur de gain. Les effets non-linéaires de type Kerr ou diffusion Brillouin stimulée peuvent être mis en évidence du fait des valeurs de la puissance crête confinée dans le cœur de la fibre. Ces deux phénomènes non-linéaires ont été étudiés pour différentes configurations d’amplificateurs. Des modèles numériques ont confirmé les déformations des signaux obtenus expérimentalement.

Pulsed kW-peak power and integrated all fiber MOPA single-frequency source at 2050nm

We report a high power, single frequency, linearly polarized master oscillator power amplifier emitting 110 ns, 1 kW peak power pulses at 2050 nm. A 20 % slope efficiency and a beam quality of M2 = 1.2 are achieved with a three stages double clad Tm3+-doped fiber architecture. Various pump schemes are compared leading to the conclusion that 793 nm pump wavelength is the most efficient for amplification at 2050 nm. Based on a numerical simulations, the Brillouin gain coefficient around 2 μm in Tm3+ highly doped silica fiber is estimated to 1.2x10-11 m/W. Output peak power is limited by Stimulated Brillouin scattering to 535 W without mitigation and to 1 kW with application of a strain distribution along the doped fiber.

Ultracompact hermetic laser diode modules for harsh environment

We report on a high brightness fiber coupled single element laser diode and its assessment on various harsh conditions. The Ultra Compact Hermetic (UCH) modules (0.7 cm3) are manufactured using a totally glue free process owing to proprietary weld processes and a controlled inner atmosphere. They deliver up to 10W out of the fiber at 25 °C and more than 8W at 60° C for λ=940nm. UCH modules emitting at 830nm also deliver more than 4.8W at 25°C. We report on the robust behavior of the UCH modules in harsh environment such as vibrations and exposure to radiations

High power pulsed fiber laser development for Co2 space based dial system

High energy fiber lasers emitting around 1579nm is seen as a possible technology for the laser unit of a spaceborn CO2 DIAL system. We are developing an all fiber system with the following expected performances: pulse energy of 260μJ, pulse duration 150ns, beam quality M2 <2, pulse linewidth <60 MHz, laser stability 200 kHz. One of our main concerns has been the radiation induced attenuation mitigation. Various fiber compositions have been investigated.