Thin Garnet Optical Isolator With Reduced Polarization Rotation
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Solution Overview
Problem
Conventional optical isolators used in laser systems are too thick for applications like handheld devices, necessitating a reduced thickness solution that maintains optical isolation while potentially increasing insertion loss.
Innovation Solution
A method and optical isolator design that utilize a garnet to rotate the polarization of optical signals by a reduced angle (45°−θ1° to 45°+θ2°) to achieve unidirectional transmission, with a polarizer and analyzer configuration that blocks ≥25 dB of reflected signal, using a thinner garnet and potentially integrating polarizer and analyzer into the garnet surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional optical isolator is used to achieve optical isolation, then unwanted optical reflections are blocked, but the device thickness becomes too large for handheld applications
Solution Approach 1:
The patent changes the polarization rotation angle parameter from the conventional 45° to a reduced angle (e.g., 22.5°), which directly enables the use of thinner garnet material while maintaining optical isolation functionality. This parameter modification resolves the contradiction between achieving sufficient isolation and reducing device thickness.
Solution Approach 2:
The patent introduces angular deviation parameters (θ1 and θ2) that allow the polarization axes of the polarizer and analyzer to be oriented at angles other than the conventional 45° relative to each other. This dimensional change in the angular space enables thickness reduction while preserving the optical isolation effect.
2Length of stationary object
If a thinner garnet is used to reduce isolator thickness, then the device becomes suitable for handheld applications, but insertion loss increases
Solution Approach 1:
By modifying the polarization rotation angle parameter and the angular orientations of the polarizer and analyzer, the patent achieves effective optical isolation with thinner garnet. The changed parameters optimize the balance between thickness reduction and insertion loss, allowing thinner garnet to be used while managing the trade-off with energy loss.
Solution Approach 2:
The patent employs adjustable angular parameters (θ1 and θ2) that can be optimized for specific application requirements. This dynamic approach allows the system to be tuned for different thickness and loss constraints, enabling optimization for handheld applications where thickness is critical.
3Length of stationary object
If the polarization rotation angle is reduced to use thinner garnet, then device thickness decreases, but the angular precision requirements increase
Solution Approach 1:
The patent moves from a fixed 45° polarization rotation configuration to a multi-parameter angular space defined by θ1 and θ2. This dimensional expansion provides additional degrees of freedom for optimization, allowing the system to achieve the desired functionality with relaxed angular precision requirements compared to conventional designs.
Solution Approach 2:
By changing from a single fixed angle parameter to multiple adjustable angle parameters, the patent creates a more flexible design space that can accommodate manufacturing tolerances. The reduced polarization rotation angle combined with adjustable polarizer and analyzer orientations provides tolerance compensation that reduces the stringency of angular precision requirements.
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 solution allows for a thinner optical isolator with maintained optical isolation, accepting increased insertion loss, suitable for applications where thickness is a constraint, such as handheld devices with semiconductor lasers.
Implementation Method 1
A optical isolator 2, an exploded view of which is shown in FIG. 1A, is based on a Faraday rotator or garnet 14 sandwiched between a first polarizer 10 and a second polarizer or analyzer 18
Implementation Method 2
polarizer 10 whose polarization axis or direction, in this example, is in the vertical direction or 0°, and which, in this example, matches the polarization 12 of the input optical signal 8
Data Source
AI summary
An optical isolator includes a polarizer for receiving and passing an optical signal received from an optical signal source to a garnet which rotates a polarization of the optical signal by an angle of 45°−θ1°, where 5°≤θ1°<42°, and outputs at least a part of this polarization rotated optical signal to an analyzer, having a polarization optical axis at 45°+θ2°, where 5°≤θ2°<42°. The analyzer outputs at least a part of the polarization rotated optical signal to an external optical circuit which reflects at least a part of the polarization rotated optical signal back to the garnet via the analyzer. The garnet rotates a polarization of the reflected optical signal by an angle of 45°−θ1° and outputs this latter polarization rotated optical signal to the polarizer which at least partially blocks it from the optical signal source.