Scanning-Beam Interference Lithography

Gratings are written with Scanning-Beam Interference Lithography (SBIL) using the nanoruler.
Utilizing an array of custom processing equipment and techniques, PGL can process a wide range of optical substrates.Current maximum size is about 93 cm x 60 cm. Plans are underway to make a machine with 1.3 to 1.5 meter capability

SBIL produces a highly accurate linewidth that results in excellent diffraction efficiency that is both uniform and repeatable from part-to-part. By precise control of the grating exposure and phase, PGL's SBIL technology is the only known technique that allows for correction of wavefront errors in substrates and apodization of incident beams. The scanning technique of SBIL overwrites with a gaussian distributed energy band of laser light that provides a high level of dose control resulting in consistent aspect ratio, high efficiency, and period repeatability of over 10ppb part-to-part.

PGL and MIT are working toward writing more complex gratings with Variable-Period Scanning-Beam Interference Lithography (VP-SBIL). VP-SBIL capacity allows for a quick changeover for periods from 200 nm to 20 µm. VP-SBIL has been tested at 100, 200, 500, 1000, 1740, 2500 and 5000 lns/mm. Due to the high degree of automation in the tool, period can be changed and ready to write on large samples in < 1 hour. PGL now writes gratings with two or more periods on the surface. Coarse gratings are used for measurement of grating thickness.

Ion Beam Etching

PGL uses a large area reactive ion etcher to etch photoresist gratings into various silicate glasses.

Here a grating is mounted in the etch chamber. The ion source is in the foreground.

The PGL Ion Etcher uses a scanning method to achieve high etch uniformity.
Etched MLD diffraction efficiency is uniform and high across the part. PGL can accurately map diffraction efficiency across large parts to determine etch uniformity.

Sandia Compressors (600mm x 210 mm)

C3 DE Average 0.97

C5 DE Average 0.98

C1 DE Average 0.965


Liquid Film Coating

PGL's meniscus coater applies photoresist to the substrate. The meniscus coater pulls the substrate over a meniscus of fluid. Small substrates are held upside down by a vacuum while large substrates are held by a groove in the substrate.





A 1.1 meter chamber is used for development of complex multilayers and energetic processes such as ion-assisted deposition.

• Two electron beam sources
• 12 cm RF Ion Source
• Optical Monitor
• 19" Dia. Planetary Rotation
• Used for development of PGL coating control software "Designlink"

Large Optic Handling

Coating Tooling is designed to allow thermal expansion of the substrate and tooling without damage to the optic. Handling tooling allow for safe handling of the substrate.

Special packaging protects substrates from contamination.



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Technical Papers

Large Area Pulse Compression Gratings Fabricated Onto Fused Silica ... (ICUIL 2008)

Reactive Ion Beam Etching of Large Diffraction Gratings (SVC 2007)

Reducing the Stress of Hafnia/Silica Multilayers ... (SVC 2005)















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