Technique for polarization locking optical outputs

Details Technique for polarization locking optical outputs Technique for polarization locking optical outputs

2000-04-20

2001-11-13

Hellner, Mark (Department: 3662)

Optical: systems and elements

Optical amplifier

Beam combination or separation

C359S346000, C359S341400

Reexamination Certificate

active

06317257

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a technique for polarization locking optical outputs. More particularly, the present invention relates to a technique for polarization locking the optical outputs of a plurality of optical amplifiers receiving an optical input signal from a common laser source.
2. Description of the Related Art
The architecture for high power phase array fiber lasers or fiber amplifiers/lasers require that the elements of the array have a common polarization. In the past, to achieve this common polarization, it was necessary to use polarization maintaining optical amplifiers or lasers in the array or to use a double pass Faraday mirror configuration to correct for the depolarization occurring in the fiber amplifiers.
In the former case, practical high power polarization maintaining optical amplifier fibers do not exist.
In the Faraday mirror case, the amplifier has to be double passed and the Faraday mirrors have to survive the high optical power input thereto. Furthermore, the architecture is complicated and requires many components.
SUMMARY OF THE INVENTION
The present invention removes the need for either measure noted above and instead corrects for any depolarization that may occur in the fiber amplifiers/lasers with an inline polarization controller for each element in the array. Each element's polarization is locked to a reference laser's polarization.
The above noted object of the present invention may be achieved in an optical polarization locked loop apparatus comprising: a laser source having an optical output; N polarization controllers respectively optically connected to N optical amplifiers, N being an integer, each of the N polarization controllers having an optical input connected to the optical output of the laser source; a reference polarization controller having an optical input connected to the optical output of the laser source and having an optical output fed back to an input thereof via a linear polarizer; N beam splitters, each beam splitter having two optical inputs and one optical output, one of the inputs being connected to an optical output of a respective one of the N optical amplifiers and another of the inputs being connected to the optical output of the reference polarization controller and an output being fed back to an input of a respective one of the polarization controllers; wherein each of the N optical amplifiers outputs is polarization locked to the optical output of the reference polarization controller.
The above noted object may also be effected by providing a method of polarization locking N optical loops to a reference loop, N being a positive integer, each of the N optical loops including a polarization controller connected to an optical amplifier, and the reference optical loop including a reference polarization controller and a linear optical polarizer, the method comprising the steps of: providing an optical output from a laser source to all of the polarization controllers; feeding back a portion of an optical output of the reference polarization controller to the reference polarization controller via the linear polarizer; feeding a portion of the optical output of the reference polarization controller to an optical input of each of N beam splitters and feeding an optical output of each amplifier of the N loops to a respective one of the N beam splitters, a substantial portion of the optical output of each amplifier being output by its respective beam splitter, wherein an interference optical output of the two optical inputs fed to each of the N beam splitters is fed back to a respective one of the polarization controllers of the N loops such that the N optical loops are polarization locked with the reference optical loop.


REFERENCES:
patent: 5212743 (1993-05-01), Heismann
patent: 5717516 (1998-02-01), Klein et al.
patent: 5946130 (1999-08-01), Rice
patent: 6061170 (2000-05-01), Rice et al.
F. Heismann, et al., “Integrated-optic polarization controller with unlimited transformation range”,Applied Physics Letters 57(9), Aug. 27, 1990, pp 855-857.

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