Phase masks or phase plates from fused silica are used in various applications in the field of optics and photonics, e.g., in the form of diffractive masks for laser micro processing or for structured illumination or the generation of specific focus geometries in high-resolution microscopy. As fused silica cannot be patterned with sufficient precision by direct laser machining, a patented process using a precursor layer of silicon suboxide (SiOx) on a quartz glass substrate is applied. The thickness of the SiOx layer has to match the required phase delay. To obtain the desired phase profile the UV absorbing layer is structured by spatially resolved laser ablation and converted into UV transparent SiO2 in a subsequent annealing process.In this way, a highly transparent and highly resistant mask made of pure quartz material is obtained. Precise process control based on optically measured layer parameters allows a precise adjustment of the phase delay with diffraction efficiencies close to the theoretical maximum.
J. Ihlemann, R. Weichenhain-Schriever:
Laser Based Rapid Fabrication of SiO2-phase Masks for Efficient UV-laser Micromachining,
Journal of Laser Micro/Nanoengineering 4, 100 (2009)
J. Ihlemann, J. Meinertz, G. Danev:
Excimer laser ablation of thick SiOx-films: etch rate measurements and simulation of the ablation threshold,
Applied Physics Letters 101, 091901 (2012)
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Laser-Laboratorium Göttingen e.V. (LLG)
Head of the Department
Dr. Peter Simon
"Short Pulses / Nanostructures"
Contact person for
Nano Structure Technology:
Dr. Jürgen Ihlemann