Microspectrometer uses single nanowire for lens-less spectral imaging: Page 2 of 2

September 24, 2019 //By Julien Happich
A team of researchers from the University of Cambridge has engineered an ultracompact microspectrometer design based on a single semiconductor nanowire about 100μm-long with a graded composition along its length.

Hence, although the devices reported in the paper were designed to operate over the full visible spectrum, they could be engineered with an almost arbitrary number of material systems, simply through adjusting source vapours during nanowire growth, yielding systems that could operate across any wavelength range from the infrared to ultraviolet, the authors highlight.

The two different nanowire spectrometers presented in the paper contained 30 and 38 photodetector units and the authors were able to resolve monochromatic light at 8.5nm and 7nm minimum reconstructed full width at half maximum (FWHM), respectively.

Despite a reduction in footprint of about two to three orders of magnitude compared to centimetre-scale spectrometers, the proof-of-concept device offered a resolution comparable to that of other visible-range spectral reconstruction microspectrometers.

Fluorescent micrograph (top) of a typical nanowire spectrometer,
incorporated into a packaged chip. Scale bar: 10 mm.
Source: Science's Nanophotonics journal.

It was demonstrated for spectral imaging, first through spatial point-scanning (scanning an image focused by a lens onto the device, across the whole focal plane). The scanning resolution was defined by the 0.3 mm mapping steps used (which could have been as small as the nanowire itself). Then the nanowire spectrometer was demonstrated in lensless spectral imaging, standing only a few micrometers over the sample and scanning at steps smaller than the nanowire itself (but always matching a fixed integer multiple of the electrode array’s pitch).

Such devices could find their way in any miniaturized spectroscopic application, including lab-on-a-chip systems, drones, implants, and wearable devices, the authors conclude.

They have applied for a patent in the UK and hope to commercialise the platform in the near future.

University of Cambridge - www.cam.ac.uk

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