Tunable Notch Filter With Adjustable Gap Distance
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Solution Overview
Problem
Current tunable notch filters have limited tuning ranges and are inadequate for selectively attenuating electromagnetic radiation across a wide spectral region, especially in the UV-LWIR range, and struggle with accurate attenuation at various incident angles, making them challenging for use in diverse optical systems.
Innovation Solution
A tunable notch filter design featuring an antenna layer and a mirror layer positioned on opposite sides of a gap, with adjustable gap distance, allowing for broad tunability and accurate selective attenuation of electromagnetic radiation across a wide spectral range, including up to 60° incident angles, using a gap that can be filled with a fluid or be a vacuum, and equipped with a gap distance sensor and adjusting device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multi-layer coatings are prepared on a transmissive window to create a notch filter, then the filter can selectively attenuate radiation at specific wavelengths, but the filter cannot be tuned to alter the spectral region and has limited adaptability
Solution Approach 1:
The patent transforms a static multi-layer coating filter into a dynamic structure by introducing a tunable cavity with movable mirrors. The cavity length can be adjusted to change the resonant frequencies, enabling the filter to dynamically select different wavelengths for attenuation. This dynamic adjustment mechanism resolves the contradiction by providing spectral tunability while maintaining a manageable device structure through controlled mobility rather than static complexity.
Solution Approach 2:
The patent changes the physical parameters of the filter system by introducing a tunable cavity with variable length. By adjusting the cavity length parameter, the resonant frequencies and thus the notched wavelengths can be changed. This parameter change approach enables spectral region alteration without requiring complete redesign of the filter structure, resolving the adaptability-complexity contradiction.
2Adaptability or versatility
If conventional notch filters are designed for specific wavelength ranges, then they provide effective attenuation at those wavelengths, but they cannot reliably attenuate radiation entering from many different angles
Solution Approach 1:
The patent creates a universal filter structure that can handle multiple incident angles through the use of a tunable cavity with adjustable mirrors. The cavity design allows the filter to maintain its attenuation function across a wide range of angles by adjusting the effective optical path length. This multi-functional capability resolves the contradiction by making the filter reliable for both normal and oblique incidence without sacrificing angular acceptance.
3Adaptability or versatility
If existing tunable notch filters are manufactured with complex optical elements such as multiple etalon filters, then they achieve some tuning capability, but they have unreasonable constraints on coupling with specific fiber or waveguide types
Solution Approach 1:
The patent segments the complex multi-etalon filter system into a simpler cavity-based structure with adjustable mirrors. This segmentation allows the filter to be designed as a modular component that can be independently tuned and integrated with different optical systems. By breaking down the complex structure into manageable segments, the patent reduces manufacturing complexity while maintaining adaptability to various fiber and waveguide types.
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 filter achieves improved operational capability with broad spectral tunability, reduced harmonic and background attenuation, and maintains radiometric efficiency, enabling its use in various optical systems by accurately attenuating radiation across a wide range of wavelengths and angles.
Implementation Method 1
an antenna layer and a mirror layer that are positioned on opposite sides of a gap and that face each other... selectively attenuate the reflection of one or more selected wavelengths of electromagnetic radiation
Implementation Method 2
The wavelength or wavelength band whose reflection is selectively attenuated, referred to as a notch, can be rapidly adjusted within and across a relatively wide spectral region
Implementation Method 3
The notch filter is tuned by adjusting the gap distance between the antenna layer and the mirror layer... The wavelength or wavelength band whose reflection is selectively attenuated, referred to as a notch, can be rapidly adjusted within and across a relatively wide spectral region
Implementation Method 4
Radiation whose reflection is selectively attenuated is absorbed by the notch filter while other radiation is reflected by the filter
Data Source
AI summary
A tunable notch filter for operation in reflection mode comprises an antenna layer positioned on a transmissive substrate and a mirror layer positioned on a support substrate. The antenna layer and the mirror layer are positioned on opposite sides of a gap and facing each other, the gap having a gap distance. The notch filter is tuned by adjusting the gap distance between the antenna layer and the mirror layer. Tuning the notch filter to a selected state can cause the filter to selectively attenuate the reflection of at least some electromagnetic radiation that is incident on the transmissive substrate and enters the notch filter.