New mechanism uses photonic crystal for concentrating light on a chip

Keeping in mind a quantity in the form of wavelengths is a challenge in itself which is important for many applications. Researchers at Amolf, TU Delft and Cornel University in the US have displayed a new way to focus on a very small scale light. Their method uses special properties of a photonic crystal and works for a wide spectrum of wavelength compared to alternative methods. Researcher Published Their conclusions in Science progress On 18 April.

It is important to focus light for various technical applications on photonic chips, such as quantum communication, optical sensors and on-chip lasers. “Until now, we knew two common strategies to concentrate lighting: it can be done using optical cavities, or with wavegides that compress light like a funnel,” called Amolf Group Leader Evold Verhane.

“The first method uses resonance, focusing or limiting concentration to a specific wavelength. The second method works, similar to a traditional lens, is much larger than the wavelength of light used in a tool.”

Stop the light

A theoretical idea of ​​researchers at the University of Cornell led by Gendi Markets pointed to the new method that Ph.D. Candidates Daniel Mu and his colleagues have now performed for the first time. An important aspect of the method is the so -called topology of the physical system.

“We use photonic crystals, which are silicon slabs with a regular pattern of very small holes, which forbid light proliferation in silicon slabs, in principle. In the crystal, the flaws are scattered or suppressed the reflection. “

Researchers thought what would happen if they suddenly eliminate such a vevgide, with a “wall” of materials that cannot undergo light. “Since the light is not going anywhere and the reflections are suppressed, it should be stored in front of that wall,” is called the mood. “The light eventually bounces back through the wavegide, but only after the delay. This results in a local amplification of the light area.”

Light concentration

The groups of Amolf in Tu Dail and Verhane in Cobus Kupers decided to verify the predictions in an experiment with the researchers of Cornell. The topological vevgides were built on a silicone chip in the amolf. To imagine the approximate accumulation of light within the photonic crystal, Muis used a unique microscope in the TU demet that scans the light areas through an ultra-split needle above the surface of the crystal. This microscope can localize the intensity of light -scale lighting about 1,000 times smaller than a human hair thickness.

“We really saw a clear amplification of the light area at the end of the topological wavegide. The interesting thing is that it only happened when the ‘wall’ that ended Wavegide was placed at a certain angle. It was actually predicted by our partners in Cornel,” says Muis.

“This proves that the light amplification is related to the topological suppression of the back reflection. The light amplification focuses in very small amounts, as is small as the wavelength of light. One of the major advantages of this method is that it is naturally broadband: it works for many different wavelengths.”

Article in Science progressWith the same contribution of Muis and his cornell colleague Yandong Lee, this form of light amplification on a chip can be read as a recipe for further research or applications. The displayed mechanism should also apply to any other type of wave in a structured medium, including electrons in sound waves or specific crystals.

“For the next step, it will be interesting to use a pulsed laser to look at the time interval in which the light accumulates, to see that the area amplification can be maximized, and to use it for applications in light manipulation on optical chips,” says Muis.