Exploring Artificial Nanophotonic Nanowire-Based Neuron

Abstract

The combination of photonics and nano-structures offers a multitude of solutions for artificial neural networks. Light is not only fast, but reduces the clutter and energy losses associated with wired connections. Energy demand is further reduced by implementing nano-components, which decreases the size of the footprint. Researchers are developing a nano-chip that combines sensing and neural computations to complete homing navigation, drawing inspiration from the insect's brain. This lightweight and energy efficient device would allow tiny robots or sensors to navigate without relying on external infrastructure like satellites.

The artificial neurons of the device consist of III-V semiconducting nanowires that receive overlapping light signals inside a 2D waveguide from external sources and from neighboring neurons. Bees rely on the sky's polarization by aligning internal photodetectors to the light's electric field to track its heading. The device mimics this functionality by employing polarization sensitive nanowires. To enhance this property, nanowires can be coupled to two metal nano-structures in a bowtie configuration that exhibit plasmonic resonances. When the electric field is aligned along the axis of this bowtie at resonant wavelengths, the localized electric field is enhanced.

This paper demonstrates this optical enhancement of the nanowire and nano-antenna system. InP nanowires are assembled with gold nano-antennas. To quantify the effect of the enhancement, the photocurrent is measured through the nanowires with excitation wavelengths between 430 nm and 700 nm. The results show a clear amplification of the photocurrent for the nanowire/nano-antenna device in comparison to the single nanowires. The report concludes with recommended actions to further optimize the device for implementation.

Popular Abstract

Can you remember the last time you used a compass to orient yourself on a hike? Have you ever found your way by looking at the stars? For most of us, the idea of finding directions has become trivial. In less than a minute, we can find our way using our phone. We don’t see animals carrying iPhones, so how do they find their way home? For some insects, it’s a matter of looking at the sky. Imagine a bee. They take a winding road scouting for nectar, yet they take a direct route home. Thanks to the polarization of light, a bee knows in which direction they are moving relative to the sun and in essence, their nest. We can mimic the bee’s neural network to build a tiny robot that can orient itself using the sky’s polarization. In this paper, we demonstrate that a nano-scale device can be sensitive to polarization like a bee by pairing a semiconductor to a metal.

Polarization describes the orientation of transverse waves – waves that oscillate perpendicular to the direction of travel. For example, when you wiggle a jump rope up and down, a wave travels along the rope with oscillations up and down. In other words, it is polarized vertically. Similarly, light is a transverse wave with oscillating electric and magnetic fields. The electric field oscillates in all directions before it enters the atmosphere, but particles like oxygen and nitrogen can “kick” or scatter the light. Scattered light travels to us with a preferred polarization, with some parts of the sky more polarized than others. This scattering effect creates a pattern over the sky that bees use like a map.

Now imagine a fiber optic wire with a diameter between 100 to 300 nanometers (nm). A nanometer is one billionth of a meter or 1000 times thinner than a human hair! If we shrink the fiber optic to 1-2 micrometers, we have what’s called a nanowire. The nanowire can operate as a miniature solar cell and convert light’s energy to a current called a photocurrent. To make the nanowire more sensitive to the light’s polarization, we place two metal triangles on either side of it pointing towards each other, like a bowtie. When the incoming electric field is polarized along the bowtie’s axis, the light and the electrons on the metal will create a plasmon that oscillates on the bowtie’s surface. These plasmons confine the light into a tiny gap between the bowtie and nanowire and in effect boost the electric field’s intensity. This is like putting your thumb over a garden hose. The water sprays out much faster. Similarly, the electric field becomes stronger in the small region. This allows the nanowire to absorb more light and generate a larger current. When we compare this instead to light being polarized along the nanowire’s axis (perpendicular to the bowtie), there is no enhancement of the electric field, so the photocurrent is weaker.

We demonstrate that our tiny optical fiber can detect light’s polarization; we observe a noticeable gain in the photocurrent when the electric field is aligned to the bowtie compared to when it is perpendicular to the bowtie. Further research is needed to optimize the device to respond to blue and green wavelengths like a bee, rather than longer wavelengths. In addition, some bowties performed better than others. Research should be conducted to analyze the properties of the metal for more uniform results. Taking inspiration from nature, we are on track to build a device that not only navigates using a celestial compass, but that requires less energy and infrastructure like satellites to operate.

• author: Cole, Kendall Marie
• supervisor: Anders Mikkelsen; Thomas Kjellberg Jensen
• organization: Synchrotron Radiation Research; Department of Physics
• course: FYSK04 20261
• year: 2026
• type: M2 - Bachelor Degree
• subject: Physics and Astronomy
• keywords: neuromorphic computing, nanowire, nano-antenna, plasmonics
• language: English
• id: 9236692
• date added to LUP: 2026-06-16 15:19:16
• date last changed: 2026-06-16 15:19:16