Diffractive beam splitters for surface texturing - HiLASE and HOLO/OR

HOLO/OR Ltd. is an Israeli company with a focus on development, design and manufacturing of diffractive optical elements (DOEs) and micro-optical elements, and have recently developed and tested a new category of diffractive beam splitters for efficient, large-area surface texturing.

Example of multi-beam created on the surface (left) and close look to the structures (right)

Based on Holo/OR’s participation in the Prometheus HO2020 project, as well as to exposure to many requests coming directly from customers, Holo/OR recognized a strong industrial demand for fast speed (>1m2/min) laser surface texturing. Surface textures can provide surface functions such as hydrophobia, increase or decrease of friction, lubricant trapping and anti-bacterial functionality. However, due to the low speeds of current methods, it is mostly employed in either high value or small size items, such as dental implants or aeroplane wings. To truly realize the ecological potential, functional surfaces must be employed in lower value, common goods such as dishwashers, washing machines, automotive parts etc. To make this economically realistic, significantly faster texturing processes are required.

A new generation of high-intensity laser systems that are currently approaching the market seem to be capable of providing the energy to pattern at such a rate. Now the challenge is to spread this energy over the area to be textured in a fast and efficient way.

There are currently several approaches for rapid texturing of large surfaces that are close to reaching industrial speed, the most promising of which is DLIP (Direct Laser Interference Patterning). However, DLIP uses non-conventional, off-axis and anamorphic optical setups, that are not easy to integrate into laser systems. As a rule, laser machine integrators prefer to work with on-axis, conventional high power laser optics requiring as little alignment as possible.

This realization has led Holo/OR to develop the DLITe concept for laser texturing, based on a single periodic DOE and a focusing lens that can be a standard F-theta lens or a high power laser focuser. This solution is simpler, lower cost, and easier to integrate compared to existing approaches for the rapid texturing of large areas.

DLITe beam splitters are specially designed diffractive optical elements (DOEs) which shape a high-power laser beam into a precise array of laser spots. These spots can be gaussian dots, lines or sharp edged flat-top shapes, such as rectangles or squares, with user-defined separations between them. DLITe are designed to enable patterning of large areas without any movement of the galvo scanner or stage. They are limited only by the laser power and focussing optics. The patterned areas can then be stitched together at a high speed by external movement, to achieve industrial processing speeds.

Holo/OR is a well-known company with excellent design and production capabilities for DOE elements as well as complementary refractive focus systems. Initially, when the DLITe concept was developed, Holo/OR had designed and simulated such a setup. Following that, an element was produced in the lab and validated with a low power 1064nm laser. At this point, to functionally test the DLITe concept, Holo/OR needed access to a mJ class ultrashort laser with high beam quality (M2<1.3).

In order to implement this solution, the expertise from Holo/OR in designing and manufacturing DOE and optical systems and from HiLASE in developing new-generation high-intensity ultrashort laser systems and in laser micromachining have been combined. At the same time, this cooperation proved the unique added value that HiLASE-designed PERLA lasers can deliver to industrial end users.

A DLITe element with pattern of 200 x 200 array of spots was successfully tested on the HiLASE-designed PERLA laser (@1030nm, 130 W, 1.8 ps) for fine structure creation on steel. Using this very simple optical system, 25cm2 was covered by fine structures in just a few seconds. Consequently, this solution is in-line with industrial demand for efficiency (>1m2/per second) and cost (1EUR/m2) as well as the request for processing large and complex 3D objects.

The specific benefits of the collaboration included

  • Opening of a new market for high intensity lasers and diffractive beam splitters
  • Offering a simpler, more cost-effective solution to integrators and laser machine builders of laser in surface texturing machines.
  • Enabling the texturing of large objects with high precision. DLITe, having few optical components and robust build, enables a light optical system that can be moved with high precision over large areas.

Additional links:
DLITe (https://www.holoor.co.il/dlite-diffractive-laser-induced-texturing)
PERLA 100 laser system (https://www.hilase.cz/en/products/perla-100)
HiLASE information page