High Extinction-Ratio Optical Rotator With Angle-Drift Compensation
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Solution Overview
Problem
Conventional optical rotators suffer from reduced extinction ratio due to changes in rotation angle caused by temperature, wavelength variations, and fabrication tolerances in Faraday rotators, leading to inaccurate polarization state compensation.
Innovation Solution
A high extinction-ratio optical rotator design incorporating a collimator, pair of polarizing splitting prisms, non-reciprocal 45-degree polarization rotator, and reflector mirror, utilizing birefringent crystal wedges and a magnetic ring to stabilize polarization rotation, eliminating angle deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Faraday rotator is used in the optical rotator, then the polarization rotation function is achieved, but the rotation angle changes due to temperature and wavelength variations, causing extinction ratio decrease
Solution Approach 1:
The patent divides the polarization rotation function into two independent parts: a Faraday rotator that provides non-reciprocal rotation and a reciprocating rotator that provides reciprocal rotation. By segmenting the rotation function, the system can compensate for Faraday rotator angle drift using the reciprocating rotator, thereby maintaining stable extinction ratio despite temperature and wavelength variations.
Solution Approach 2:
The patent implements a feedback mechanism where the reciprocating rotator compensates for the angle changes in the Faraday rotator. The system monitors the polarization state and adjusts the reciprocating rotator angle to counteract Faraday rotator drift, creating a closed-loop compensation system that maintains stable extinction ratio.
2Reliability
If a linear polarizer is used to filter laser light, then polarization filtering is achieved, but 50% of intensity is lost
Solution Approach 1:
The patent replaces the traditional linear polarizer (which absorbs 50% of light intensity) with a polarization beam splitter combined with a quarter-wave plate. This substitution uses optical path separation instead of absorption-based filtering, allowing the system to achieve polarization filtering while preserving laser intensity and reducing energy loss.
3Ease of manufacture
If fabrication tolerance variations occur in the Faraday rotator, then manufacturing is simplified, but the rotation angle becomes inaccurate, reducing extinction ratio
Solution Approach 1:
The patent introduces adjustable parameters in the reciprocating rotator that can be tuned to compensate for fabrication tolerances in the Faraday rotator. By making the reciprocating rotator angle adjustable, the system can calibrate and correct for manufacturing variations, achieving high extinction ratio without requiring extremely tight fabrication tolerances on the Faraday rotator.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design stabilizes polarization rotation, achieving a high extinction ratio by compensating for temperature and wavelength-induced angle deviations, thereby improving optical performance.
Implementation Method 1
The collimator can be in the form of an optical fiber with its end faces connected with an endcap or a TEC (thermal expanded core) optical fiber to expand the beam of the light at the fiber face, which can reduce the optical energy density at the end face of the fiber and significantly increase the laser damage threshold.
Implementation Method 2
The pair of polarizing splitting prisms separates the two orthogonal polarization components of the input signal light into a vertically polarized light and a horizontally polarized light by the polarizing splitting prism and the two polarized is orthogonal.
Implementation Method 3
The pair of polarizing splitting prisms can be made of birefringent crystal wedges.
Implementation Method 4
A magnetic ring can provide a magnetic field for the polarization rotator at the upper and the lower sides of the non-reciprocal 45-degree polarization rotator, so that the non-reciprocal 45-degree polarization rotator can achieve a non-reciprocal rotation of the polarization direction.
Implementation Method 5
The vertically polarized light and the horizontally polarized light exiting the non-reciprocal 45-degree polarization rotator intersect on a surface of the reflector and are reflected back into the non-reciprocal 45-degree polarization rotator.
Implementation Method 6
The interaction between signal light and the rotating plate causes the magnetic field intensity on the rotating plate to change, and the changed magnetic field generates a vortex electric field. The C-shaped magnetic ring can horizontally polarize the vortex electric field from forming a closed loop on the magnetic ring, and thus preventing a vortex current from heating the magnetic ring.
Data Source
AI summary
A high extinction-ratio rotator includes a collimator that can collimate a signal light from an optical fiber, a pair of polarizing splitting prisms that include a first birefringence crystal wedge and a second birefringent crystal wedge, that can separate two orthogonal polarization components of the signal light into a vertically polarized light and a horizontally polarized light, a non-reciprocal 45-degree polarization rotator which the vertically polarized light and the horizontally polarized light exiting the pair of polarizing splitting prisms pass through, and a reflector. The vertically polarized light and the horizontally polarized light exiting the non-reciprocal 45-degree polarization rotator intersect on a surface of the reflector and are reflected back into the non-reciprocal 45-degree polarization rotator.