NewsResearchers Develop World's Smallest Silicon LED for High-Resolution Lens-Less Holographic Microscope

Researchers Develop World’s Smallest Silicon LED for High-Resolution Lens-Less Holographic Microscope

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Researchers from the Singapore-MIT Alliance for Technology and Research (SMART) claim that they have created what could be the world’s most compact subwavelength silicon LED that can be used in a lens-free optical microscope, based on research conducted by their researchers. The lens-less holographic camera uses mathematical algorithms to construct images of objects using interference patterns without the need for traditional optics. This kind of microscope can create high-resolution images of specimens like plant seeds or tissue samples and live cell tracking. It can also provide images of biological tissues using spectroscopic technology or even tracking live cells. Additionally, this kind of microscope is smaller and cheaper than the traditional microscopes, which makes it a perfect instrument for conducting biological research and medical applications.
This type of microscope does not employ traditional optics. Instead maths is employed to create images using the patterns that objects create. SMART has created the deep neural network structure for this purpose – this time of tissues and plant seeds.

The LED for room temperature was constructed with an unmodified commercial 55nm bulk CMOS process as well as electronics as well as other photonic components on a 300mm-wide wafer emitting infrared light at a rate of 50mW/cm2. A small area of emission, less than 0.14mm2 (400nm in the diameter) has resulted in significant power output of this device.

Surface passivation has been a crucial element in LED manufacturing, since nonradiative recombination caused by surface imperfections has become a bigger risk as the dimensions shrink. Carriers were contained in the gate oxide layer as well as the electric field created by a top contact for injecting carriers comprised of transparent polysilicon, rather than opaque metal, to improve emission. A gate oxide layer, typically made up of silicon dioxide, is formed during the fabrication of metal-oxide-semiconductor (MOS) devices. It’s usually deposited directly on the top of a surface like silicon wafer. This layer is used to separate the gate electrode which regulates the flow of current between drain and source contacts, from the under-layer of channel space in the substrate. The thickness as well as the quality are crucial in determining the performance of electrical circuits and reliability of MOS devices.

Traditional techniques for image reconstruction require the precise knowledge of an experiment setup to achieve accurate reconstruction typically fail due to the difficulty of variables to control, such as optical aberrations, noise as well as issues with the “twin image” issue. According to the SMART website: “Natural light imaging systems such as SiLEDs and holographic microscope 2On image reconstruction require significant knowledge for precise results, while traditional reconstruction methods rely on subjective assumptions.”

Team’s neural network considers the system’s variables and is able to be used without having prior knowledge of the beam or spectrum of the light source’s profile. It is not required to train since the algorithm has an embedded physical model.

“In addition to holographic image reconstruction, the neutral network offers blind source spectrum recovery from a single diffracted intensity pattern – marking a departure from all prior supervised learning techniques,” according to SMART, which has similar LED-neural networks microscopes that are used to monitor live cells as well as the spectroscopic examination of biological tissues like living plants.

The LED’s description stated that they have a variety of uses for arraying within CMOS to create programmable light sources for complicated systems as well being used as “further applications for creating coherent illumination through programable coherent arraying.”

Michal Pukala
Electronics and Telecommunications engineer with Electro-energetics Master degree graduation. Lightning designer experienced engineer. Currently working in IT industry.