Researchers at Freie Universität Berlin and HTW Berlin have published a new use of the Delta 7: laser writing of erasable luminescence patterns into perovskite films. The paper, "Patterning metastable photoluminescence shapes into mixed-halide perovskites using spatial laser beam shaping", is published open access in Optical Materials 180 (2026) 118465.

From microscopy to materials

Mixed-halide perovskites change their emission under light. Illumination drives the halide ions apart, and the exposed region starts to glow at a different wavelength. The Berlin team turns this well-known instability into a writing mechanism. A 405 nm laser beam, shaped by a Delta 7 deformable phase plate, is focused onto the film through a microscope objective. Where the light lands, an iodide-rich phase forms and emits above 750 nm; two cameras behind a dichroic mirror image the print in both spectral channels at once. Within minutes the halides remix and the pattern erases itself, so the same spot can be written again. The authors call the method Adaptive Perovskite Patterning.

Why a deformable phase plate

The Delta 7 shapes the beam by phase modulation described with Zernike polynomials. In the study, an astigmatism term stretches the focus into an ellipse, and a second term turns that ellipse by 45°; other profiles follow from other Zernike terms, switched electronically and without a mask. Shaping by phase rather than by a mask keeps the excitation power, which matters when the light budget is small. And the authors name two advantages of the deformable phase plate over liquid-crystal modulators for this job:

  • Polarization independence. Unpolarized sources, even LEDs, could drive the writing.
  • Near-UV. The Delta 7 works at the 405 nm excitation wavelength used in the study.

The authors present the study as a proof of concept and set out where it goes next: mapping how the excitation intensity controls the write and erase kinetics, and how many write–erase cycles a film sustains.

A new field for the DPP

Mask-free, erasable photopatterning points towards reprogrammable photonic structures: transient displays, self-erasing QR codes, optical anti-counterfeiting. For the DPP it is a new field as well. Not imaging, not aberration correction, but laser writing in materials.

This is the second paper from the Lindinger group with a Delta 7, after their 2023 work on shaped pulses for polarization-enhanced two-photon fluorescence.

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