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Applied Photonics > Research and Development > R&D on Fiber lasers and related activities > Technology

Technology Overview

Activities at Multitel in the field of fibre lasers and amplifiers include modelling, design and prototyping. Different sources have already been developed for specific applications like:

  • Narrow linewidth lasers based on a single longitudinal mode source, externally modulated and amplified for Doppler LIDAR.
  • Broadband sources for optical tomography.
  • High power CW, all-in-fibre sources for materials welding.
  • Short (ns) and ultra-short (ps, fs) sources for micro-machining applications.

We aim at building, when possible, all-in-fibre sources by taking advantage of our technological knowledge on fibres handling (fibre Bragg gratings, tapering, combining of fibres, splicing with special LMA and also Photonic Crystal Fibres, etc), in order to propose compact, compatible and reliable solutions.

Erbium, Ytterbium and Thulium

The Applied Photonics Department has a large expertise on rare-earth doped fibre lasers and amplifiers. Starting with Erbium, the researchers of MULTITEL have exploited their original expertise on EDFAs for addressing new applications. Then this knowledge on fibre amplification, modelling and handling has been transposed to Ytterbium, opening the path towards new fields like micromachining. For achieving this, Multitel has learned during the last decade how to handle special fibres, with splicing, tapering, mode converting issues, to make performant all-in-fibre laser sources. The Thulium fibre laser activity has fully start in September 2010 with the project IMPROV, contributing to enlarging the scope of possible applications.

The applied Photonics Department disposes of fully equipped facilities, including two clean rooms for high power laser assembly and all the equipment for fibres handling and lasers characterization. In particular the team if fully equipped for characterisation of lasers sources from 350 nm to 2.4 ┬Ám. 

CW, narrow linewidth and single frequency lasers

Developing stable, narrow linewidth and even single frequency laser sources is also part of the skills of MULTITEL: For instance we already developed a single frequency laser source with 8 kHz spectral linewidth, externally modulated and amplified up to 170 ┬ÁJ with Large Mode Area (LMA) fibres. The laser maximum average power was limited by Stimulated Brillouin Scattering (SBS). The threshold of SBS apparition has been pushed to the limit with the use of LMA fibres and a careful handling of the temporal shape of the pulses to compensate for deformation due to gain. As a result, the laser combined narrow linewidth, high energy, eye-safe operation and good beam quality: M┬▓ < 1.3, in a fully fibred configuration.

Other CW laser sources have already been demonstrated like:

  • High power fibre laser delivering up to 140 W at 1.06 ┬Ám. The laser is fully fibres and can also be operated in Q-switched mode, delivering a few nanosecond pulses at adjustable repetition rates.
  • All-in fibre linearly poarized CW lasers based on new device from the US company Chiral Photonics: the results were presented at EUROPHOTON 2010.
  • High power CW Raman laser sources operating at 1270 nm.

Short and ultrashort pulsed lasers

In terms of pulsed sources, the engineers of the Applied Photonics Department have already developed several lasers based on different pulsing mechanisms: active and passive Q-switching, mode-locking and gain switching. As a consequence, we can propose the most appropriate solution in function of the R&D project objectives and applications.

For example, a fully fibred active Q-switch device have been recently demonstrated in a joint work with ACREO Fibre center. A "high" repetition rate (> hundreds of kHz) Q-switched laser, delivering 10 ns short pulses and amplified up to 20 W in a fully fibred configuration has been presented at Photonics Europe 2010. Different mode-locking lasers have already been realized. In particular a 6 MHz 40 ps laser has been recently developed and amplified up to 60 W in the IR and frequency tripled to 20 W. This joint work with the company EOLITE has been published in CLEO US 2010. 

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Pulse (a) and spectral characteristics (b) of an all-in-fibre laser delivering 35 ps and 5 W at 80 MHz.

We also demonstrated gain switched lasers with adjustable pulse width from 200 ps to 10 ns and adjustable repetition rates from 100 kHz to 1 MHz. Such lasers have also been amplified in MOPA configurations for various applications like supercontinuum generation (from 350 nm to 2.4 ┬Ám) or material processing (thin film solar cells). Finally we also have experience on chirp pulse and parabolic amplification. An all-fibre CPA system was presented at Photonics Europe 2008. The laser consisted of an ultrashort pulse oscillator, a stretcher, an amplifier and compressor, all fully fibred. The laser amplification stage was simultaneously operating as a compressor. Interesting results like 300 fs, 10 MHz, 1.5 W average power at 1.55 ┬Ám have been demonstrated and the device received a prize as the "Best Marketability Product" presented at the Photonics Innovation Village. Such approach is of particular interest for compact and ultrashort pulse sources for THz or micromachining applications.  

(a)  (b)

Pulse (a) and output power characteristics (b) of an all-in-fibre CPA delivering 72 fs and 100 mW at 50 MHz.

Other results and developments on-going can be found through our publications and projects; we are always open to establish new collaborations in the field.

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