Products

Products

Pulse Compression Gratings

PGL is currently manufacturing and supplying multilayer coated dielectric (MLD) Gratings to several of the world’s largest ultra high-intensity laser projects. These gratings are made under license to Lawrence Livermore National Laboratory. The combination of coating and grating fabrication makes it possible to greatly improve damage threshold, diffraction effciency, and wavefront of the compressed short pulse. PGL also fabricates gold gratings over photoresist or metal over etched silica for broadband applications.

A 91cm x 42cm MLD grating for laser pulse compression on the laser at the Institute for Laser Engineering at Osaka University

These gratings are produced on a custom basis. Please call us with your requirements.

Current capacities:

Active area	Up to 920mm x 600mm
Spatial Frequency	50 to 5000 lns/mm
Grating Type	MLD, Etch Phase Grating (Transmission), or Metal (Gold, Alluminum...)
Wavefront Distortion	< 1/4 wave (depending on aspect ratio)
Diffraction Efficiency	Typically 90 to 96%

Grating Variations

Since the gratings are written with a small fringe-locked spot many possibilities exist for writing focussing or chirped gratings. Gratings may even be written with a distributed phase function to provide for uniform illumination of larger targets.

2-D Gratings

2-D Grating shapes for a high contrast fringe pattern as a function of exposure

An etched 2-D Grating Array as seen in a Scanning Electron Micrograph.
The grating is etched into fused silica and then coated with aluminum.

Grating Fabrication

PGL has demonstrated both high efficiency and high damage threshold. Large aperture gratings have been fabricated and tested with excellent diffraction efficiency >96% into the 1st order. The laser-induced damage threshold has been tested at 600 fs and 10 ps. The results are among the highest ever tested for an MLD grating.

Gratings written on the Nanoruler have a very flat wavefront when measured in Littrow

GR3 has been written with an excellent result.

	P-V Waves
Holographic	0.149
CCW	0.144
CW	0.173

The two Littrow measurements, CW and CCW, allow the holographic component (line straightness) to be separated from substrate irregularity.

Dose Control

The Nanoruler has exceptional control of the dose delivered to the resist. This is seen in an exposure test as seen below. The slowly varying duty cycle is especially important when trying to acheive very high diffraction effciencies.
Exposure test at 1740 lines/mm on BF/MLD/120ARC/500PR3/5/08 1.3 mm apertures;
178t-08-nr2; Doses 150 to 50 mJ/cm2

Ghost-free grating - Because of the multiple fringe averaging which takes place during scanning, Nanoruled gratings are free from ghosts that form from defects in collimating optics in conventional exposure methods.These ghost can lose energy due to scattering, affect wavefront, and potentially can form hotspots in downstream optics

Grating Design

PGL can model complex grating designs which can include dielectric stacks or metals.
This design information is provided to the customer if requested.

Gold Grating, S-Polarization

Coating Design

Coating Fabrication

Coating Process Development

PGL develops full coating processes for large optical coaters. A 2 meter chamber here is being prepared with coating processes for complex multilayers and energetic processes such as ion-assisted deposition.

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