Optical spectrometers are indispensable instruments used in a wide range of applications, from medical diagnosis to material characterization. However, conventional spectrometer designs are often bulky and expensive, limiting their usability outside specialized facilities. In recent years, researchers have been exploring ways to develop more compact and affordable optical spectrometers that can be easily deployed on a larger scale.
A group of researchers from the Chinese University of Hong Kong and other institutes in China recently introduced a groundbreaking micro-sized, portable optical spectrometer in a paper published in Nature Electronics. This new spectrometer is based on an organic photodetector with a bias-tunable spectral response, offering a promising alternative to traditional spectrometer designs.
The key innovation behind this new optical spectrometer lies in the manipulation of photocarrier generation in photodiodes using a trilayer contact structure. By combining a transparent back contact, an optical spacer, and a back reflector with a Schottky diode and an organic ternary bulk heterojunction, the researchers created a photomultiplication-type organic photodetector (PM-OPD). This novel technology allows for the computational reconstruction of incident light spectra from measured photocurrents under different bias voltages.
One of the most impressive features of this new optical spectrometer is its size, with a footprint of only 0.0004 cm2. Despite its compact design, the spectrometer is capable of operating across the entire visible wavelength with a remarkable sub-5-nm resolution. This level of performance opens up new possibilities for portable and wearable applications that were previously unattainable with conventional spectrometer designs.
In a series of rigorous tests, the researchers found that their miniaturized optical spectrometer demonstrated outstanding performance across the entire visible spectrum regime, from ~400–760 nm. To showcase the versatility of their design, they used it to fabricate an 8 x 8 spectroscopic sensor array for hyperspectral imaging. This technique enables the detection of unique spectral signatures of specific objects by analyzing information across the electromagnetic spectrum.
The development of this miniaturized and cost-effective optical spectrometer opens up new possibilities for the advancement of research and medical practices. By inspiring the creation of similar devices, this innovative approach could lead to the development of cutting-edge technologies that were previously inaccessible due to the limitations of traditional spectrometer designs. Ultimately, the future of optical spectrometers appears to be heading towards a more compact, efficient, and affordable direction, thanks to the groundbreaking work of these researchers.
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