The researchers at Sandia National Laboratories have achieved a significant milestone in the fields of nanophotonics and ultrafast optics by dynamically steering incoherent light, which is light emitted by common sources such as incandescent or LED bulbs, with random wavelengths and phases. This is unlike coherent light, which comes from lasers and has photons with the same frequency and phase.
Active manipulation of incoherent light sources has been a challenge, as existing phase-sensitive metasurfaces (artificially structured materials made from semiconductor building blocks called meta-atoms) were designed for coherent light sources. These metasurfaces are capable of exerting dynamic control over the properties of light at sub-wavelength scales using spatial phase engineering.
To overcome this challenge, the researchers predicted and experimentally demonstrated sub-picosecond steering of ultrafast incoherent emission from a light-emitting metasurface over a 70° range. They used a monolithic III-V (Gallium Arsenide) metasurface with embedded Indium Arsenide (InAs) quantum dot light sources, positioned on a reflective Bragg (Aluminum Arsenide/Aluminum Gallium Arsenide) mirror. This arrangement allowed them to achieve a large optically induced phase change near the emission wavelength (1.25 μm).
To control the light, they utilized a spatial light modulator to structure a strong optical pump (800 nm) and projected it onto the resonant metasurface, creating reconfigurable spatial momentum profiles that dynamically steered the ultrafast (140 fs) quantum dot emission. The ability to actively control incoherent light sources in such a rapid manner is a significant advancement for the fields of nanophotonics and ultrafast optics.
This dynamic spatiotemporal control of incoherent light sources can enable new technologies in various fields, such as high-speed communications, holography, and remote sensing. Potential applications include improving military helmet screens, creating small displays for augmented and virtual reality devices that project holographic images using low-power LEDs, and enhancing LIDAR systems used in self-driving cars for object detection.
While it may be considered hyperbole to call this breakthrough “revolutionary,” the advancements made here do represent a significant step forward in the field. The ability to control incoherent light sources, which are typically more affordable and energy-efficient than coherent light sources, has the potential to impact various applications, including holographic and AR displays. The team envisions commercial products based on this technology within 5–10 years.
Research Into Incoherent Light Sources
Research into incoherent light sources for AR and holographic displays might not be as prominent as research into coherent light sources like lasers. However, there has been a growing interest in developing alternative light sources and methods for such displays to make them more cost-effective, energy-efficient, and compact. The research conducted by Sandia demonstrates a potential breakthrough that could pave the way for more research into incoherent light sources for these applications.
It may be that further research of holographic displays using Spatial Light Modulators (SLMs) and Digital Micromirror Devices (DMDs) leads to other technologies that can modulate incoherent light, although they often still require coherent light sources like lasers for high-quality hologram generation. As the field of AR and holographic displays continues to advance, it is likely that more research will explore alternative light sources, including incoherent light.
