Thermally Driven Light Mill Optical Limiter
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Solution Overview
Problem
Existing optical limiters either require exotic materials or are single-use, making them impractical for reusable applications in optical networks where radiant flux needs to be limited to prevent damage to network components.
Innovation Solution
A thermally driven light mill is used to route an optical signal, where the radiant flux is limited by rotating vanes with temperature asymmetry, allowing for a reusable optical limiter that does not rely on exotic materials, and can be designed to either limit output power or completely interrupt the beam if exceeded.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical limiters use exotic materials with negative thermal index coefficients or light absorbing materials, then radiant flux limiting capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces complex optical materials with a simple mechanical system consisting of a mirror and a vane that rotates in response to radiation pressure. The mirror is attached to the vane, and as the vane rotates due to thermal expansion from absorbed light, the mirror deflects the optical beam away from the output, achieving radiant flux limiting without exotic materials.
Solution Approach 2:
The patent utilizes thermal expansion parameter changes of the vane material in response to absorbed optical energy. When the vane absorbs light, its temperature increases causing thermal expansion, which changes its rotational position. This parameter change (temperature-induced expansion) directly controls the mirror's deflection angle, creating a passive, material-free limiting mechanism.
2Reliability
If optical fuses use light absorbing materials destroyed by heat or become opaque, then radiant flux interruption capability is improved, but device reusability deteriorates
Solution Approach 1:
The patent employs a self-regulating mechanism where the vane automatically rotates in response to excessive radiant flux without external intervention. The thermal expansion of the vane material itself provides the actuation force, eliminating the need for external power sources, control systems, or replacement mechanisms. The device continuously monitors and responds to radiant flux levels, providing indefinite reusability.
Solution Approach 2:
The patent replaces the consumable light-absorbing material of optical fuses with a durable mechanical system. Instead of relying on material degradation or phase change, the system uses radiation pressure and thermal expansion to drive a mechanical rotation that deflects the beam. This mechanical approach allows repeated operation without degradation.
3Reliability
If optical limiters rotate mirrors in response to radiation pressure, then radiant flux limiting is achieved, but device complexity increases
Solution Approach 1:
The patent merges the radiation pressure response mechanism with the beam deflection function into a single integrated structure. The mirror is directly attached to the vane, so that the vane's thermal expansion automatically drives the mirror's deflection. This merging eliminates separate actuation mechanisms, control electronics, and power supplies, achieving radiant flux limiting with minimal device complexity.
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 provides a reusable optical limiter that effectively limits radiant flux without the need for exotic materials, offering a practical solution for preventing damage to optical network components by adjusting the output power or interrupting the beam as necessary.
Implementation Method 1
A first vane of the light mill is configured to be illuminated by a control beam... and to absorb energy from that light so that it heats up
Implementation Method 2
at least one region of at least one face of at least one vane of each light mill is configured to have light incident upon it, and to absorb energy from that light so that it heats up relative to an opposing region
Implementation Method 3
The vanes are located in fluid (typically low-pressure air) such that convection currents set up in the fluid by the asymmetry in temperature between the two sides of each vane are sufficient to cause the light mill to rotate.
Data Source
Figure 1A1~1C
Figure 2A~3B
Figure 3C~3D
AI summary
An aspect relates to an optical limiter (200) for limiting the radiant flux of an optical source beam, comprising: an optical control port (221) for illumination by an optical control beam originating from the source beam; an optical input port (221) for illumination by an optical transmission beam originating from the source beam; an optical output port (225) for illumination by the transmission beam; and a thermally driven light mill (211, 212); wherein the light mill is arranged with respect to the input port, the control port and the output port such that: illumination of the control port by the control beam drives the light mill to rotate only when the control beam has a radiant flux equal to or in excess of a predetermined radiant flux threshold; and rotation of the light mill causes an area of the output port illuminated by the transmission beam to change.