Laser Device Triggered by a Photonic Fibre

A device for cyclically generating short duration laser pulses, typically smaller than 30 ns, the device including a laser resonator of optical length smaller than 2 m including two reflecting ends and incorporating an MPF photonic fibre pumped continuously by at least one pump wave derived from power semi-conductive laser diodes focussed by optical means for collimating the fibre, the MPF fibre including a medium where an internal laser beam is guided and having a gain with very weak signal greater than 10 per passage through the gain medium, the laser resonator also incorporating an optical modulator, the optical modulator being able to deflect the axis of the internal laser beam, said optical modulator is actuated by an electric control, along two stable directions, the first direction corresponding to an axis along which the internal laser beam undergoes sufficient losses to prevent the laser effect from being triggered, the device then being in an open cavity mode, and the second direction corresponding to an axis along which the internal laser beam is reflected towards itself at least partially by an optical return means closing the resonator at a first one of its ends, the device then being in a closed cavity mode, the second end of the laser resonator being closed by a means at least partially reflecting situated on the other side of the amplifying medium,

• characterised in that the modulator possesses a switching time greater than the time taken by light to travel through the cavity, and that it is used in a configuration where the loss factor introduced in the state corresponding to the open cavity mode is greater than the gain with very weak signal of the resonator, in that the amplifying medium preserves the state of polarisation, and in that it includes means for generating harmonic radiation with non-linear crystals.