World’s smallest LED will convert your phone camera into a microscope
This may remove the need for traditional microscopes which are currently used to look at microorganisms and tissue cells.
A team of researchers from Singapore-MIT Alliance for Research and Technology (SMART) has developed a silicon LED that can help convert the camera of the mobile phone in your hand into a high-resolution microscope.
With light intensity comparable to much larger silicon LEDs, this LED was used in what the researchers are calling the world’s smallest holographic microscope which has multiple potential applications.
The team also developed a neural networking algorithm to reconstruct objects measured by the holographic microscope. Neural networks are a type of machine learning and their design is inspired by the way the neurons in our brain signal to one another. This removed the need for heavy traditional microscopes, enabling their all-in-one chip to look at microscopic objects like microorganisms and tissue cells.
Successfully solving a challenge
The innovation paves the way for advancement in photonics – an area of technology that deals with studying and technological harnessing of light. The press release says that the building of a powerful on-chip emitter that is smaller than a micrometer has long been a challenge in the field, which the research team has had a breakthrough in.
Previously, scientists have struggled to place such on-chip emitters into standard complementary metal-oxide-semiconductor (CMOS) platforms, which is the semiconductor technology used in most chips today. In mobile phones, CMOS is used as the ‘eye’ of the camera.
The researchers think that this combination of CMOS micro-LEDs and their newly developed neural network can be applied in other areas as well, such as live-cell tracking or spectroscopic imaging of biological tissues.
“On top of its immense potential in lensless holography, our new LED has a wide range of other possible applications. Because its wavelength is within the minimum absorption window of biological tissues, together with its high intensity and nanoscale emission area, our LED could be ideal for bio-imaging and bio-sensing applications, including near-field microscopy and implantable CMOS devices,” said Rajeev Ram, a co-author of the paper. “Also, it is possible to integrate this LED with on-chip photodetectors, and it could then find further applications in on-chip communication, NIR proximity sensing, and on-wafer testing of photonics.”
Established in 2007, SMART was set up in collaboration with the Massachusetts Institute of Technology in Cambridge and is its largest international research endeavor.
The study was recently published in the journal Optica.
Study Abstract:
A nanoscale on-chip light source with high intensity is desired for various applications in integrated photonics systems. However, it is challenging to realize such an emitter using materials and fabrication processes compatible with the standard integrated circuit technology. In this letter, we report an electrically driven Si light-emitting diode with sub-wavelength emission area fabricated in an open-foundry microelectronics complementary metal-oxide-semiconductor platform. The light-emitting diode emission spectrum is centered around 1100 nm and the emission area is smaller than 0.14 μm2 (~∅400 nm). This light-emitting diode has high spatial intensity of >50 mW/cm2 which is comparable with state-of-the-art Si-based emitters with much larger emission areas. Due to sub-wavelength confinement, the emission exhibits a high degree of spatial coherence, which is demonstrated by incorporating the light-emitting diode into a compact lensless in-line holographic microscope. This centimeter-scale, all-silicon microscope utilizes a single emitter to simultaneously illuminate ~9.5 million pixels of a complementary metal-oxide-semiconductor imager.
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