Integrated Micro-Optoelectronic Sensors
IMS’s in-depth expertise in group III nitride- and silicon carbide-based materials, epitaxial growth techniques, fabrication processes, and packaging of integrated micro devices opens up an alternative path for designers of optical (photonic)-based sensors to consider. The schematic below outlines the adopted novel platform of the integrated microsensors advantages and applications.
The core architecture of our sensor technology is based on the growth and integration of a number of multi-stacked thin film microstructures on a single small-size chip (substrate). These multi-configured microstructures represent active solid state light sources (LEDs) and photodetectors configured to match the targeted sensor application. The spectral specifications of the sensor/s can be determined, controlled, and fine tuned within a wide range of wavelengths (200 – 1700) nm by proper design of the thin film structures using advanced and conventional deposition processes. Depending on the application, the substrate, which these structures are grown on would be either transparent to the band of wavelengths emitted by the light source/s or it may be opaque as depicted in the sketches below.
The spectral emission and response of the each of the integrated LEDs and photodetectors can be fine tuned to set and control the optical and physical properties of these structures. Growth techniques controlling the thickness and relative composition of elements in each compound determine the integrity and spectral properties of these structures. The ability to fine tune the design and fabrication of these structures to match a specific sensor application, is a fundamental advantage in utilizing the binary (AlN, GaN, and InN) and ternary (AlxGa1-xN and InxGa1-xN) alloys from the group III nitride. The figures below are spectra from commercial LEDs (left) and photodetectors (right) used in one of the sensor simulator prototypes.
The optical emission from the LEDs interact with the test media either directly or indirectly through the transparent sapphire window. Both contact surfaces (sapphire & nitride-based structures) contacting the test media are physically durable and chemically inert. Different sensing modalities, like fluorescence, luminescence, scattering, absorption, can be accommodated without any major changes in the configuration. Driving of the LEDs and handling of the detected signals is provided by advanced electronic circuitry compatible with these structures based on Field Programmable Gate Arrays (FPGA), which permits the integration of Analog-to-Digital Convertors (ADC), amplifiers, logic, acquisition devices, and intelligent analysis system based on Artificial Neural Networks (ANN). A number of diverse applications in the chemical, biological, and medical applications are prime candidates for the efficient utility of this category of sensors.
This technology sets forth a number of key advantages over conventional platforms, especially for multifunctional sensing systems, geared toward real-time, in-situ, and reversible sensing within harsh environments. The following are some of these advantages inherited in its unique ability to:
Reduce the bulkiness and consequently cost and reliability of a system. Each sensor comprising one or more pairs of LED-Photodetector can operate with raw light without the need for discrete delivery channels (optical fibers), optical elements (splitters, lenses, gratings, filters, polarizer, and etc).
Cover a wider spectral band ranging from UV to IR represented by a bandwidth of light from (200 -1700) nm to match a broader range of materials, sensitivities, and specificities.
Custom-design system parameters, by tailoring integration of microstructures configurations and layout in one package.
Withstand tougher environmental conditions related to elevated temperature (~350 oC), higher mechanical stresses and pressure, harsher chemical and corrosion conditions, and higher radiation levels.
Accommodate different modalities of reversible sensors based on luminescence, fluorescence, absorption, polarization, scattering, and other phenomena.
The miniaturized platform lends itself to the ease of integration with established stationary or remote setups and portable hand-held instruments.
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