Tunable Microstructured Optical Waveguide via Periodic Plugs
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Solution Overview
Problem
Conventional optical devices with periodic refractive index variations, such as Bragg gratings, are permanent and require UV exposure or hydrogen loading, limiting their tunability and flexibility in modifying optical signals.
Innovation Solution
Incorporating periodic 'plugs' of optically active material into the cladding structure of optical waveguides, allowing for tunable and resonant structures by varying the refractive index through temperature, light, or magnetic fields, without the need for UV exposure or photosensitive cores.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional Bragg gratings or long period gratings are used to introduce periodic refractive index variations, then the phase/amplitude of optical signals can be modified, but the gratings are permanent and require UV exposure or hydrogen loading, limiting tunability and flexibility
Solution Approach 1:
The patent introduces dynamic tunability by allowing the periodic structure to be adjusted after fabrication. The grating period can be modified by applying thermal expansion to the fiber coating, which dynamically changes the periodicity of the refractive index modulation without requiring permanent UV exposure or hydrogen loading processes.
Solution Approach 2:
The patent changes the physical parameters of the grating structure by utilizing thermal expansion of the fiber coating material. By controlling the temperature, the periodicity parameter of the grating can be adjusted, enabling tunable filtering and other optical modulation functions without permanent modification of the fiber core.
2Reliability
If UV exposure is used to create permanent grating structures, then the refractive index can be periodically varied, but the process is time-consuming and requires specific equipment
Solution Approach 1:
The patent replaces the UV exposure process with a mechanical/thermal approach. Instead of using UV lasers to permanently write the grating, the invention uses thermal expansion of the fiber coating to create a permanent periodic structure, eliminating the need for UV equipment and reducing processing time.
Solution Approach 2:
The fiber coating material itself provides the periodic structure through its thermal expansion properties. The coating expands and contracts in a periodic manner when temperature is applied, automatically creating the desired grating structure without requiring external UV writing equipment or complex processing procedures.
3Productivity
If the refractive index perturbation difference is made large to achieve coupling in a short length, then coupling efficiency improves, but the complexity of introducing the periodic structure increases
Solution Approach 1:
The patent optimizes the refractive index perturbation by changing the material properties of the fiber coating. By selecting materials with appropriate thermal expansion coefficients and optical properties, the invention achieves large refractive index differences that enable short coupling lengths while maintaining a simple periodic structure introduction process.
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
Enables efficient coupling between different polarizations and modes, achieving tunable transmission properties and wavelength tuning by adjusting the periodicity of the optically active material, enhancing the flexibility and efficiency of optical signal manipulation.
Implementation Method 1
manipulate the evanescent fields (propagation constants, polarization, etc) of light propagating along the guide/fiber
Implementation Method 2
change the optical properties of a propagating optical signal, where the active material is infused using a 'periodic' process so as to create separate, periodic 'plugs' of optically active material
Implementation Method 3
heating the air in the channels on both ends of a tapered microstructure fiber section, so as to induce pressure on both sides of the periodic structure, which results in compressing the air between the plugs and changing the period of the microfluidic structure
Implementation Method 4
The periodicity may be used in accordance with the present invention to provide coupling between the different polarizations of the propagating mode and create a polarization rotator
Data Source
AI summary
A microstructured optical waveguide is formed to include a periodic sequence of “plugs” of optically active material within the inner cladding air tunnels. The plugs are utilized as a grating structure for generating resonant and periodic structures. The waveguide (in one embodiment, an optical fiber) is tunable by changing the spacing of the plugs (e.g., heating the structure, changing the pressure within the structure, etc.), or by modifying the initial spacing of the plugs during the formation of the microstructured optical waveguide (i.e., by modifying the “dipping frequency” of the waveguide into a reservoir of optically active material). In general, any number of different types of optically active material may be used to form the plugs, where two or more different materials may be used in the same structure, and introduced in an alternating fashion.