Atomic Layer Deposition (ALD) Technology

Fabricating a band-pass filter with a narrow linewidth (<0.2 nm) over a large area (>5 inches) presents significant challenges. By leveraging Atomic Layer Deposition (ALD) technology, Raytum Photonics has successfully fabricated band-pass filters that achieve a 0.2 nm bandwidth at 465 nm across a 6-inch substrate and the transmission rate is as high as 80%. ALD's precise thickness control enables exceptional uniformity and conformity of coatings across large areas and on complex surfaces, including curved internal surfaces like the Winston cone. Additionally, the low growth temperatures make ALD particularly well-suited for applying optical coatings to large glass tiles, temperature-sensitive plastics, and other materials. This technology opens new possibilities for achieving high-performance optical coatings with unparalleled precision and versatility.

ALD process has also been extensively investigated for the fabrication of Surface Enhanced Raman Scattering (SERS) active substrates including Au or Ag nano-particles, ultra-thin films, conformal coatings of 3D scaffolds, and high-density hot spots on nanostructured scaffold, etc. Raytum Photonics developed a flow-through glass fiber coating fixture that can force all precursors pass through porous fibers to coat Ag nano-particles deeper and more uniform across a large area thus to maximize hotspot density and volume in 3D direction which is critical to increase accessibility of biochemical analytes and SERS sensitivity.

Patents and publications:

1. High Damage Threshold and Highly Reliable Broad-band Mid-IR Coatings for High Power Fluoride Fiber Laser, Patent Pending, 17/691,537

​2.   Methods for Fabricating Surface-enhanced Raman Spectroscopy Substrates, Patent Pending, 18/224,645

3.   Feng Niu, Yimin Hu, Stephen LeKarz, and Wei Lu, "High Enhancement, Low Cost, Large Area Surface Enhanced Raman Scattering Substrates All by Atomic Layer Deposition on Porous Filter Paper", JVST: A (Vol.42, Issue 2),

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Dichroic Filter

SEM micrograph from Ag coated glass fiber filter paper showing excellent conformality.

Band-pass Filter

SEM micrograph from Ag coated glass fiber filter paper showing excellent conformality.