Fraunhofer presents evaluation kits for spatial light modulators

The tiny micro mirrors of the spatial light modulators can manipulate light on a pixel-by-pixel basis. They play a key role for the generation of high-precision light patterns for applications in lithography, medical technology, astronomy, or quantum computing.

Fraunhofer IPMS develops spatial light modulators with several million individually analog-controllable mirrors on a single semiconductor chip. The components form optical key elements for various applications and offer high versatility. Depending on the application, the micro mirrors can be tilted along one or two axes or lowered horizontally. This enables them to control and manipulate light in its direction, intensity or phase, creating precise light patterns.

To facilitate the transfer of this highly integrated, fast and precise technology into new applications, Fraunhofer IPMS offers its customers evaluation kits with 64k (256 x 256) mirrors. Researchers in the Spatial Light Modulators business unit are excited to present a significant innovation: the systems, usually based on one-axis tilt mirrors, have now been expanded to include piston mirrors as a new type of actuator. The successful technology implementation into the first version of the evaluation kit allows customers to test a large part of the portfolio of micro mirror arrays on a single, central platform.

With this versatile solution, Fraunhofer IPMS offers a unique testing platform.

"Normally, different mirror technologies also require corresponding test systems because the individual mirror arrays are based on individual CMOS backplanes. Our kits allow users and developers to test the spatial light modulators on a central platform," said Dr. Michael Wagner from Fraunhofer IPMS.

Depending on the mirror type and system setup, the evaluation kits can be used from the ultraviolet spectral range through the visible spectrum up to the near infrared. The researchers are currently working on extending the application range of the evaluation kit to the deep ultraviolet range, as other SLM-platforms from Fraunhofer IPMS are already used within this range. In the ultraviolet range, smaller details can be resolved, allowing a detailed and high-precision imaging.

Furthermore, the advanced control electronics of the evaluation kit further support very high modulation frequencies up to the kilohertz range.

"Typically, the modulation frequency of a micro mirror array is limited by the control setup, not by the properties of the chips themselves. A powerful setup can exploit the full capabilities of the micro mirrors," said Mario Nitzsche, scientist. The evaluation kits achieve high performance through nanometer-accurate calibration of the micro mirrors, ensuring precise and high-resolution analog (quasi-continuous) lowering or tilting movement.

The complete evaluation kit comprises the control electronics, a 64k micro mirror chip (256 x 256 pixels), and the appropriate software. Support for integration and for optimal operation is provided.

The spatial light modulators from Fraunhofer IPMS are used in various applications. In microscopy, 1-axis tilt mirror arrays are employed to selectively illuminate samples. The semiconductor industry, and specifically microlithography, benefit from the expertise of Fraunhofer IPMS in modulator development for the deep ultraviolet range: The analog-controllable mirror arrays enable an improved performance of mask writing tools. With 2-axis tiltable mirror arrays, precise redistribution of incoming laser light with minimal intensity losses can be realised, which is for example beneficial for material processing. Piston mirror arrays, on the other hand, can implement precise phase modulations, which allow the generation of 3D holography images.

They are considered a promising key component for real 3D head-up displays. So-called 'real' 3D displays generate an actual hologram within the three-dimensional space, unlike previous 2D modulations that create a depth effect through special visual effects. Precise phase modulation is also of great relevance for other application fields such as adaptive optics in astronomy, in medical technology, or the generation of optical traps for quantum computing purposes.