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Optical-fibre passively mode locked laser generator with non-linear polarization switching
| Details |
Inventors: Fontana, Flavio;
Assignee: Pirelli Cavi S.p.A. (Milan, IT)
Primary Examiner: Scott, Jr.; Leon
Assistant Examiner:
Attorney, Agent or Firm: Finnegan, Henderson, Farabow, Garrett and Dunner
A passively-mode-locked laser generator having an active optical fibre and fibre pumping means adapted to cause the generation of an emission signal in the fibre, a polarization control means, signal extraction means and at least one optical component with transmissiveness depending on polarization is disclosed. The components are inserted in an optical fibre path that, for a pumping energy lower than a predetermined value corresponding to a linear propagation condition of the signal, gives rise to a polarization rotation of the emission signal through an angle causing the extinction of the signal itself within the optical component with transmissiveness depending on polarization. For a pumping energy of a higher power than the predetermined value, the generator causes a polarization rotation of the emission signal through an angle corresponding to the transmission with low losses of only pulses of high peak power of the emission signal. |
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DETAILED DESCRIPTION The present invention concerns an active-fibre laser that is passively-mode-locked and particularly suited for emission of solitons.
In an aspect the present invention concerns an active-fibre passively-mode-locked laser generator comprising an active optical fibre doped with a fluorescent dopant; means for feeding luminous pumping energy to one end of the active fibre, the pumping energy being adapted to excite the active-fibre fluorescent dopant to a laser emission state such that the dopant may decay to a base state with a luminous emission to a predetermined wavelength constituting an emission signal of pulses of different peak powers, of a value depending on the pumping energy.
The laser generator further comprises a polarization control means for orienting the polarization of the emission signal in a predetermined plane; an optical feedback device connected to the ends of the active fibre; at least one optical component with transmissiveness depending on polarization; and means for extracting the emission signal from the active fibre, in which at least the active fibre, polarization control means, feedback means and optical component with transmissiveness depending on polarization are components of an optical fibre path in which the emission signal propagates and in which at least one portion of the emission signal present at one end of the active fibre is sent back to the interior of the fibre.
The laser generator of the present invention is characterized in that the components of the optical path have an orientation that, on the whole, gives rise to a rotation of the polarization of the emission signal which, in case of pumping energy lower than a predetermined value causing a linear-condition propagation of the emission signal in the optical path, takes place through an angle corresponding to the extinction of the emission signal within the optical component with transmissiveness depending on polarization and to the consequent absence of emission signal in the extraction means
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