Double-pass optical fibre amplifier and optical-device architectures

An optical device comprising:

• an acousto-optic modulator (AOM);
• a laser generating an optical beam;
• an optical fibre, called upstream fibre, extending between the laser and the AOM, in which one or more optical beams is or are intended to propagate towards and/or originating from the AOM;
• a splitter which unilaterally connects the laser to the upstream fibre so that the optical beam emitted by the laser propagates in the upstream fibre in the direction of the AOM;
• an optical fibre, called downstream fibre, situated downstream of the AOM with respect to a direction linking the upstream fibre to the AOM, in which the optical beam(s) is/are intended to propagate towards and/or originating from the AOM;
• a reflection means connected to the downstream fibre of the AOM and arranged to reflect a beam originating from the downstream fibre into the downstream fibre;
• the upstream fibre is a polarization-maintaining optical fibre configured for maintaining a linear polarization state of an optical beam;
• and
• the downstream fibre is arranged so that a transit time of the optical beam in said downstream fibre from the AOM up to the reflection means is non-zero and less than or equal to half of an open time of the AOM;
• and/or
• the AOM comprises a crystal in which:
• at least one of two opposite faces, called the input/output faces, through which one or more optical beams is or are intended to enter and/or exit the crystal, forms a non-zero angle with a direction of propagation of the acoustic wave in the crystal, called direction of propagation;
• the input/output faces of the AOM are comprised in a plane extending from a face of the crystal, called injection face, in contact with a piezoelectric oscillator generating an acoustic wave propagating in the crystal up to a face of the crystal, called absorption face, on which an acoustic absorber at least partly absorbing the acoustic wave after it has propagated in the crystal from the injection face up to the absorption face is arranged.