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Engineers can now change individual photon frequencies with a new optical device, giving them new capabilities.
One of the essential lessons a grade school science student will learn is that white light does not exist. Instead, it is a mixture of photons. These are the tiny droplets of energy that make light. They come from all colors of the rainbow: red, orange, yellow, green, and blue.
Researchers at Stanford University have now developed an optical device that allows engineers to alter and fine-tune each photon’s frequencies in a stream of light, allowing them to create any combination of colors they desire. The new photonic architecture, published in Nature Communications on April 23, 2021, can transform fields such as digital communications, artificial Intelligence, and quantum computing.
Shanhui Fan, an engineer and professor at Stanford, said that “this powerful new tool puts an engineer in control of a degree not previously possible.”
Cloverleaf Effect
It consists of a wire for light that carries a stream of photons. The photons are then directed through rings that look like highway cloverleaf off-ramps. Each round contains a modulator, which transforms the frequency and wavelength of passing photons into colors. Engineers can adjust the modulators to achieve the desired frequency transformation.
The researchers envisage an optical neural network for artificial Intelligence that uses light instead of electrons. The existing methods for creating optical neural networks don’t alter the frequency of the photons but merely reroute photons at a single frequency. Researchers believe that such neural computations could result in smaller devices.
Avik Dutt (post-doctoral scholar in Fan’s lab and second author of this paper) stated that “our device is a significant departure from existing methods with small footprints and yet offers tremendous new engineering flexibility.”
See the light
The frequency at which a photon resonates determines the color. This is, in turn, a function of the wavelength. A photon of red has a slow frequency and a wavelength of around 650 nanometers. Blue light, which has a faster frequency and a wavelength of approximately 450 nanometers, is at the opposite end of the spectrum.
A straightforward transformation could be shifting a photon’s frequency from 500 to 510 nanometers. Or, as the human eye would see it, from cyan to grün. This is the power of Stanford’s architecture. It can perform simple transformations but also more complex ones with fine control.
Fan gives an example of an inbound light stream that contains 20 percent photons within the 500-nanometer range and 80 percent at about 510 nanometers. Engineers could adjust this ratio to 73% at 500 nanometers and 27% at 510 nanometers if desired. All while keeping the total number of photons. The percentage could be 37 percent or 63 percent. This device is new and very promising because it can set the balance. In quantum worlds, one photon can have multiple colors. The new device allows you to change the ratio of different colors in a single photon.
“We claim that this device allows for arbitrary transformation, but that doesn’t mean random,” said Siddharth, a graduate student at Fan’s lab during the research. He is now a researcher at Facebook Reality Labs. We mean that we can perform any linear transformation required by the engineer. This allows for a lot of engineering control.
It’s versatile. Fan said that the engineer could precisely control frequencies and proportions and perform various transformations. It gives engineers new power. It is up to them how they use it.
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