Photonic computing is carried out through multiple polarization channels, leading to an enhancement in computing density by several orders compared to that of conventional electronic chips. The computing speeds are faster because these nanowires are modulated by nanosecond optical pulses. Since the creation of the first integrated circuit, packing more transistors into a given size of an electronic chip has been the go-to means of maximizing computing density the so-called “Moore’s Law.” However, with Artificial Intelligence and Machine Learning requiring specialized hardware that is beginning to push the boundaries of established computing, the dominant question in this area of electronic engineering has been “How do we pack more functionalities into a single transistor?”
Light has an exploitable property different wavelengths of light do not interact with each other a characteristic used by fiberoptics to carry parallel streams of data. Similarly, different polarizations of light do not interact with each other either. Each polarization can be used as an independent information channel, enabling more information to be stored in multiple channels, hugely enhancing information density. There are several advantages of photonics over electronics, for example light is faster and more functional over large bandwidths. So, if we could fully harness such advantages of photonics combining with tunable material we can realize faster and denser information processing. In a paper published in Science Advances, researchers led by Professor Harish Bhaskaran at the University of Oxford have developed a method using the polarization of light to maximize information storage density and computing performance using nanowires. The research team developed a HAD (hybridized-active-dielectric) nanowire, using a hybrid glassy material which shows switchable material properties upon the illumination of optical pulses. Each nanowire shows selective responses to a specific polarization direction, so information can be simultaneously processed using multiple polarizations in different directions.
The research team demonstrated polarization-selective switching in hybridized-active-dielectric (HAD) nanowires, wherein the optical absorption in the nanowires is tuned on the basis of the polarization of input optical pulses. This is the first proof of concept for polarization-selective switching, incorporating tunability in a HAD nanostructure. Using this approach, they showed reconfigurable and nonvolatile polarization-division demultiplexing of electrical conductivity with up to five independent levels.
The research team successfully extend the electrically coupled and polarization-decoupled design to demonstrate matrix-vector multiplication (MAC-type operations) with input polarization as the tunable vector element. The University of Oxford findings unlock an additional degree of freedom in phase-change photonics and pave the path for a breadth of applications that fully exploit multifaceted properties of light.
Lee JS, Farmakidis N, Wright CD, Bhaskaran H. Polarization-selective reconfigurability in hybridized-active-dielectric nanowires. Science Advances 2022;8(24):eabn9459. doi: 10.1126/sciadv.abn9459.