The photolithographic device's art renderings, on one of the arms, transform the incident waveguide fundamental (only one of the mode fields in the waveguide cross-section) into a second order mode (the mode field is split into two in the waveguide cross section) On the other arm, the incident waveguide fundamental is converted into a strong surface wave that can be used for on-chip chemistry and biosensing.
A research team at Columbia University's Engineering School, led by Nanfang Yu, an assistant professor of applied physics, invented a method to efficiently control the propagation of light in restricted paths or waveguides using nanowires. To demonstrate this technology, they created photonic integrated devices that break the minimum size record while still maintaining optimal performance over an unprecedented wide wavelength range.
Photonic integrated circuits (PICs) are based on light propagating in optical waveguides, and controlling such light propagation is a central issue in the manufacture of these chips that use photons instead of electrons to transmit data. Yu's approach is likely to bring faster, more powerful and more efficient optical chips, which in turn may change the optical communications and optical signal processing. The study was published online in the April 17 issue of Nature * Nanotechnology magazine.
"We created an integrated photonic device with the smallest size and the largest operating bandwidth," Yu said. "The extent to which we now have the ability to shrink the size of the photonic integrated device with the help of nanowire antennas is similar to what happened when large vacuum tubes were replaced with smaller semiconductors in the 1950s." This work is a basic science The problem provides a revolutionary solution: how to control light propagation in waveguides in the most efficient way?
The optical power of a lightwave propagating along a waveguide is confined to the core of the waveguide: the researcher can only access the guided lightwave through the small "evanescent" tail of the evanescent wave near the surface of the waveguide. These elusive guided waves are particularly difficult to maneuver, so photonic integrated devices tend to be bulky and space-consuming, limiting the device's integrated density of the chip. Reducing the size of photonic integrated devices to have a history similar to that of electronics following Moore's Law - doubling the number of transistors in electronic integrated circuits every two years has become one of the major challenges researchers are trying to overcome.
Yu's team found that the most effective way to control lightwaves is to "decorate" the waveguides with optical nanowires: these tiny antennas extract light from the waveguide core, modify the properties of the light, and release the light back into the waveguide. The cumulative effect of densely packed nanowire arrays is so strong that they can perform functions such as waveguide mode conversion at distances up to twice the wavelength.
"This is a breakthrough, in contrast to traditional methods that require devices that are tens of times longer in wavelength to achieve waveguide mode switching," Yu said.
"We've been able to reduce the size of the device 10x to 100x."
Yu's team has created a converter that can convert one particular waveguide mode to another waveguide mode; this is the key to the technology called 'Modular Demultiplexing (MDM).' An optical waveguide can support a fundamental mode and A set of higher order modes, just as a guitar string supports a basic tone and its overtone, is a solution that dramatically increases the optical chip's information processing capabilities: We can use the same color of light, but with several different waveguide modes To transmit several separate channels at the same time through the same waveguide. "The effect is like, for example, the George Washington Bridge magically has the ability to handle several times more traffic," Yu explains. "Our waveguide The mode converter allows us to make information channels of higher capacity. "
He plans to integrate tunable active optical materials into photonic integrated devices in the next step, making active control of light propagation in the waveguide possible. Such an active device would be the basic building block of Augmented Reality (AR) glasses, a goggles that first determine the wearer's ocular aberration and then project the aberration-corrected image into the eye - this is He and colleagues at Columbia University's School of Engineering, Professor Michal Lipson, Alex Gaeta, Demetri Basov, Jim Hone, and Harish Krishnaswamy are researching topics. Yu is also exploring the conversion of waves propagating in the waveguide into strong surface waves, which could eventually be used for on-chip chemical and biological sensing.
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