All-Optical Near-Infrared Imaging via Semiconductor Nanocrystals

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This project will develop new technology for Near Infrared (NIR) light imaging that is ultra-compact, transparent, and multi-colour. Human eyes only see 0.0035% (visible light) of the electromagnetic spectrum around us. Among all invisible spectra, the NIR range is of particular interest because of its broad application, for example for medical diagnosis, food quality control, autonomous vehicles, and night-vision. In conventional NIR-imaging technology, the NIR light gets converted to electrons and the resultant image is projected onto a display, where electrons get converted to light again to be viewed by the eye. Therefore, the converted images are monochrome. Moreover, this display blocks the perception of visible light, therefore disrupting normal vision. Also, such cameras are either only operational in a short wavelength band (e.g. Ge or InGaAs, converting up to 1800nm) or require cooling (e.g. InAs or InSb detectors operating at -200 C). Moreover, NIR cameras must be bulky to accommodate all components for light/electron conversions.The detectors used in today's technology mean that the aforementioned limitations cannot be avoided. This project will develop a new technology for NIR-imaging that is all-optical, i.e. no longer requires optical and electric signals to be converted to each other. This technology will employ engineered nanocrystals, embedded within a thin and transparent layer, that capture the infrared light and re-emit it in the visible range. This approach will offer new functionalities as a result of:i. being ultra-compact;ii. forming colour images from invisible objects;iii. being transparent in both visible and NIR ranges;iv. capturing the visual information in the range of 400-4000nm, that is 10 times wider than the visible spectrum.Such a revolutionary technology will be provided as a transparent thin and flexible layer that can upgrade any glass surface e.g. goggles and windows, to an NIR-imaging device, enabling a view over both visible and infrared frequencies concurrently. Therefore, information that is currently invisible to the naked eye will become visible - the ripeness of fruits and species health. This technology will also enable us to see invisible objects in the dark. Imagine no light pollution and a massive reduction in greenhouse gases associated with a world where the lighting was not required to see at night.To develop this technology, specific nanocrystals to convert the colour of the light from NIR to visible will be designed and engineered. These nanocrystals, which are often a few hundred times smaller than a human hair, are transparent, i.e. do not block normal vision. The technique to fabricate and verify high-quality nanocrystals on a transparent surface (e.g. glass) has recently been invented by the applicant. In order to enhance the capability of these nanocrystals for capturing ultra-weak NIR light, the NIR will be mixed with an extra laser beam (also invisible) to generate a visual intensity in the visible range. Alongside this, various engineered nanocrystals within the same array, which enable conversion of different NIR frequencies into different visible frequencies will be employed. This will allow the generation of colour images from NIR objects. Finally, the extra laser beam and the nanocrystals will be embedded within a transparent, thin and flexible polymer cast that can be accommodated on any non-flat surface (for example windshields and goggles) and enable vision over the NIR range, without using bulky cameras. Industrial prototyping will be done in collaboration with Flexotronix, and industrial performance evaluations and environmental tests will be done in collaboration with QinetiQ, and Horiba Mira, respectively.