Wavelength-Selective Optical Sensor for Narrowband IR Detection
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Solution Overview
Problem
Existing infrared spectroscopy technologies face challenges in achieving high wavelength resolution, directivity, and multi-wavelength measurement, particularly in miniaturized sensors, due to complex structures and materials that require multiple deposition processes, leading to broad bandwidth and poor angular resolution.
Innovation Solution
A photosensor with a two-dimensional lattice pattern of raised portions on a perfect absorber, combined with a heat detection mechanism, allows for high wavelength selectivity and directivity, absorbing 90% or more of perpendicularly incident light, and can be arrayed for multi-wavelength detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dielectric photonic structure or metal plasmonic structure is used as a perfect absorber, then wavelength selectivity is improved, but the microfabrication pattern and process becomes complex
Solution Approach 1:
The perfect absorber is segmented into multiple layers including a metal layer, dielectric layer, and raised portions with periodic structures. This segmentation allows each layer to contribute specifically to wavelength selectivity while simplifying the overall fabrication process compared to complex monolithic structures.
Solution Approach 2:
A dielectric layer is introduced as an intermediary between the metal layer and the raised portions. This dielectric mediator enables wavelength selectivity through its optical properties while providing a simpler fabrication pathway than direct metal-plasmonic structures, bridging the gap between metal and dielectric approaches.
2Manufacturing precision
If the resolution of the sensor is about 0.5 μm with Q factor of about 10, then the sensor can be fabricated with current technology, but the bandwidth becomes much broader than the vibration of solid molecules
Solution Approach 1:
The Q factor is changed from about 10 to 50 or more by modifying the periodic structure parameters of the raised portions. This parameter change narrows the bandwidth to match molecular vibration frequencies while maintaining manufacturability through standard lithography processes that can resolve the required dimensions.
3Measurement precision
If multi-wavelength measurement is performed, then the accuracy of temperature measurement and gas detection is improved, but the device complexity increases
Solution Approach 1:
The photosensor is designed with multi-functionality to perform both temperature measurement and gas detection using the same structural platform. The periodic structures can be tuned to different wavelengths, allowing a single device to execute multiple measurement functions without requiring separate specialized sensors for each application.
Solution Approach 2:
Multi-wavelength capability is achieved by introducing dimensional variation through the periodic structures in the raised portions rather than adding multiple separate sensor elements. This dimensional approach to wavelength multiplexing reduces device complexity compared to arranging multiple independent sensors.
4Volume of moving object
If a two-wavelength type radiation thermometer is used, then the size is reduced compared to Fourier transform spectroscopy, but the accuracy is not guaranteed when emissivity changes with respect to wavelength
Solution Approach 1:
The sensor enables dynamic multi-wavelength measurement by utilizing the temporal response characteristics of the pyroelectric element. The system can sequentially measure at different wavelengths within the response time of the detector, achieving accurate temperature measurement despite emissivity variations while maintaining a compact form factor.
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 photosensor achieves high spectral sensitivity with flexible wavelength selectivity, enabling ultra-small spectrometers and multi-color imaging, and can detect objects with high accuracy without cooling, suitable for motion and gesture sensing.
Implementation Method 1
a photothermal conversion type infrared sensor in which a heat sensing material and a perfect absorber that absorbs light of a specific wavelength and generates heat are combined
Implementation Method 2
a pyroelectric element that generates heat according to received light
Implementation Method 3
the surface of the absorber includes a periodic structure in which a plurality of raised portions is arranged at a predetermined period
Implementation Method 4
a resonance wavelength, and absorbs light having the same wavelength as the resonance wavelength
Data Source
Figure 1(a)~1(d)
Figure 2
Figure 3
AI summary
A photothermal converter using a wavelength selective perfect absorber made of a low-loss metal material or dielectric and a heat detection sensor are combined to develop a sensor that efficiently converts light of a specific wavelength into heat and further electrically detects the heat. Here, since the wavelength selective perfect absorber of the present invention has a periodic structure, it has high directivity, and can also be used as a small motion sensor or a watching sensor using detection of thermal radiation. In addition, it can also be used as a high-precision small position sensor by being combined with a laser light source matching the resonance wavelength of the sensor.