The scientists used a "direct laser writing" method to arrange voxels with a specific refractive index in a borosilicate glass in 3D

Integrated photonics, optical computing and digital holography are modern techniques that require manipulation of optical signals in three dimensions.

For this to happen, the optical flow must be able to be shaped and directed according to its preferred application. If the refractive index controls the optical flow in the medium, specific refractive index adjustments are required to identify the control of the optical path in the medium.

To this end, the researchers developed "aperiodic photon volume elements" (APves), microscopic voxels with a specific refractive index at a predetermined location that direct light flow in a controlled manner.

But sculpting such elements requires a high degree of accuracy, and most light-shaping materials are limited to 2D configurations or end up lowering the output beam profile.

In a study recently published in Advanced Photonics Nexus (APNexus), scientists led by Alexander Jesacher of the Medical University of Innsbruck in Austria propose a simple way to manufacture high-precision APves for a range of applications.

The technique uses a method called "direct laser writing" to arrange voxels with a specific refractive index in a borosilicate glass in 3D.

The scientists developed an algorithm to excite optical flow through the medium to determine the maximum position of the voxel in order to achieve the necessary level of accuracy. Based on this, they were able to produce 154,000 to 308,000 voxel in just 20 minutes, with each voxel absorbing a volume of about 1.75 µm by 7.5 µm by 10 µm.

In addition, the team used dynamic wavefront control to compensate for any spherical aberrations (beam profile distortion) during laser focusing on the substrate. This ensures the consistency of each voxel profile at all depths within the medium.

The research team developed three APVes to illustrate the applicability of the method: The intensity shaper used to adjust the intensity distribution of the input beam, the RGB multiplexer beam used to process the red-green-blue (RGB) spectrum transmission of the input beam and the Hermite -- Gaussian (HG) mode sorter to improve the data transmission speed.

The intensity shaper is used to convert a Gaussian beam into a microscopic smiley-face light distribution, which is tracked by a multiplexer to make up the various parts of the smiley-face distribution of various colors. Finally, the HG mode classifier converts several Gaussian mode inputs into a pattern that has been transmitted by an optical fiber to the HG mode.

In all cases, these devices are capable of transmitting input signals without considerable loss. They achieved record diffraction efficiency of up to 80%, thus setting a new bar for APVE standards.

Segovia-Olvera added, "Demonstrating a proven method for producing consistent, reproducible, and reliable APVes not only adds to current knowledge in the field, but also opens up new avenues for applying photonics."

In addition to simplicity, lowest cost and high accuracy, the method has the potential to be extended to other substrates, such as nonlinear materials.

Source: Laser Net