Researchers have developed the world’s first photodetector that can see all shades of light, in a prototype unit that radically shrinks one of the most basic elements of modern technology.
Photodetectors work by converting information transported by light into an electrical signal and used in a wide range of technologies, from game consoles to fiber optic communications, medical imaging and motion detectors. At present, photodetectors cannot detect more than one color in a device.
This means that they have been larger and slower than other technologies, such as the silicon chip, with which they are integrated.
The new hyper-efficient broadband photodetector developed by researchers at RMIT University is at least 1000 times thinner than the smallest commercially available photodetector unit.
In a significant step for the technology, the prototype unit can also see all shades of light between ultraviolet and near infrared, which opens up new possibilities for integrating electrical and optical components on the same chip.
The cutting-edge technology opens up for improved biomedical imaging and promotes early detection of health problems such as cancer.
Study Leading Author, Ph.D. researcher Vaishnavi Krishnamurthi, said in photodetection techniques, making a material thinner usually came at the expense of performance.
“But we managed to design a device that packs a powerful stroke, even though it is thinner than a nanometer, which is about a million times smaller than the width of a needle head,” she said.
In addition to shrinking medical imaging equipment, the ultra-thin prototype opens up opportunities for more efficient motion detectors, low-light imaging and potentially faster fiber-optic communication.
“Smaller photodetectors in biomedical imaging equipment can lead to more precise targeting of cancer cells during radiation therapy,” says Krishnamurthi.
“Shrinking technology can also help deliver smaller, portable medical imaging systems that can be easily taken into remote areas compared to the bulky equipment we have today.”
Illuminates the spectrum
How versatile and useful photodetectors are depends largely on three factors: their working speed, their sensitivity to lower light levels and how much of the spectrum they can sense.
When engineers have tried to improve the capacity of a photodetector in one of these areas, at least one of the other functions has decreased.
Current photodetector technology is based on a stacked structure with three to four layers.
Imagine a sandwich, where you have bread, butter, cheese and another layer of bread – no matter how good you are at crushing that sandwich, it will always be four layers thick, and if you remove one layer you would compromise on quality .
Researchers from RMIT’s School of Engineering scrapped the stacked model and worked out how to use a nanotin layer – just a single atom thick – on a chip.
It is important that they did this without reducing the speed of the photodetector, sensitivity to low light or the visibility of the spectrum.
The prototype device can interpret light ranging from deep ultraviolet to near infrared wavelengths, making it sensitive to a wider spectrum than a human eye.
And that makes it more than 10,000 times faster than a moment.
A major challenge for the team was to ensure that electronic and optical properties did not deteriorate when the photodetector was shrinking, a technical bottleneck that had previously prevented the miniaturization of light detection techniques.
Chief researcher Associate Professor Sumeet Walia said that the material used, tin monosulfide, is cheap and naturally abundant, which makes it attractive for electronics and optoelectronics.
“The material allows the device to be extremely sensitive in low light conditions, making it suitable for shooting in low light over a wide light spectrum,” he said.
Walia said his team is now looking at industry applications for their photodetector, which can be integrated with existing technologies such as CMOS chips.
“With further development, we can look at applications including more efficient motion detection in security cameras at night and faster, more efficient data storage,” he said.
New photodetector can improve night vision, warmth and medical imaging
Liquid metal synthesized ultra-thin SnS layers for high-performance broadband photodetectors, Advanced materials, DOI: 10.1002 / adma.202004247
Provided by RMIT University
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