Researchers have developed a method for printing optical holographic lenses that could greatly simplify their fabrication. Because the method can be performed quickly and easily, it could potentially be used by astronauts to print lenses while in space for holographic lens telescopes.
While current holographic lens fabrication methods are often expensive, time-consuming, and labor-intensive, the new printing method can produce a lens in just a few seconds using only a single step. The method uses a nanosecond laser pulse to create interference patterns on a transparent substrate coated with light-absorbing materials. The laser is reflected off a concave mirror back onto itself, so that interference occurs between two laser beams traveling in opposite directions. The resulting interference pattern, consisting of circular fringes, is “printed” on a substrate between the two beams, storing the optical information as a holographic lens. The resulting flat, ultra-thin lenses consist of hundreds of nanoscale circular zones that contribute to focusing light.
Using this new method, the researchers demonstrated that they could achieve mass production within a few minutes. The method should also work with a wide variety of materials on substrates that are semitransparent, with geometries that are flat, curved, or of other arbitrary form.
Besides having niche applications like printing telescope lenses in space, the new printing method could also be used for security, data storage, and biosensors. Due to the flexibility of the fabrication method, lenses can be printed on certain materials that are not compatible with conventional fabrication techniques. In the future, the scientists plan to use the method to print lenses on thin films of semiconductors, with applications in applied optics and infrared imaging.
Holography plays a significant role in applications such as data storage, light trapping, security, and biosensors. However, conventional fabrication methods remain time-consuming, costly, and complex, limiting the fabrication of holograms and their extensive use. Here, we demonstrate a single-pulse laser ablation technique to write parallel surface gratings and Fresnel zone plates. We utilized a 6 ns high-energy green laser pulse to form interference patterns to record a surface grating with 820 nm periodicity and asymmetric zone plate holograms on 4.5 nm gold-coated substrates. The holographic recording process was completed within seconds. The optical characteristics of the interference patterns have been computationally modeled, and well-ordered polychromatic diffraction was observed from the fabricated holograms. The zone plate showed a significant diffraction angle of 32° from the normal incident for the focal point. The nanosecond laser interference ablation for rapid hologram fabrication holds great potential in a vast range of optical devices.
Laser printed holograms will also enable smart windows
It’s hoped this new hologram-creation method could be miniaturized into a smartphone, or even used to create 3D artwork and “smart windows”. It also has applications in holographic data storage. “We and our collaborators are currently pursuing all these research paths and achieving good results,” said Butt.
SOURCES – Phys org, ACS Nano, Digital News World