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Fraunhofer ILT increases laser micromachining efficiency

The Fraunhofer Institute of Laser Technology ILT has increased the efficiency of laser micromachining through the development of new self-aligning helical optics, diffractive optical elements and spatial light modulators. These advancements will be presented at the Laser World of Photonics show in Shanghai, China this year, which will play host to around 850 exhibitors and 45,000 visitors on 14 to 16 March.

An example of helical optics: Cutting microgears in sapphire glass for luxury watches (Credit: Fraunhofer ILT)

One of the boosts to micromachining efficiency has come from the institute's development of self-aligning helical optics systems, which can achieve smooth beam profiles through the rotation of a central Dove prism at up to 10,000rpm. The aspect ratio and conicity of a machined borehole can then be controlled by adjusting the tilt of the beam.

Using a Trumpf TruMicro 5270 ultrashort pulse laser, the system can create hole diameters ranging from 10µm to 500µm in sapphire or hardened glass with smooth surfaces and no cracks. This has been demonstrated in the cutting of delicate sapphire glass microgears for luxury watches.

The helical system is still only a prototype, however it has already been delivered to numerous Asian research groups in the fields of micro and consumer electronics.

Further efficiency increases have been enabled by the institute's latest diffractive optical elements (DOEs), which can be used to generate static spot patters helpful to surface texturing applications and the drilling of multiple similar holes. These DOEs are one of Fraunhofer ILT's solutions that can divide strong laser beams into numerous beamlets for parallel processing.

Another solution from the institute uses spatial light modulators based on liquid crystals to generate spot beam patterns that can be switched up to 50 times per second and programmed to almost any shape. When coupled with a galvanometer scanner, the system is able to scan a workpiece rapidly while dynamically changing the number or shape of laser spots. Multi-beam optics such as these can be used in microelectronics, automotive and consumer goods applications.

A programmable multi-beam optics with galvanometer scanner can split the laser into any number of beamlets. The resulting pattern can be changed and positioned anywhere on the workpiece. (Credit: Fraunhofer ILT)

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