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.
||Up to 920mm x 600mm
||50 to 5000 lns/mm
||MLD, Etch Phase Grating (Transmission),
or Metal (Gold, Alluminum...)
||< 1/4 wave (depending on
||Typically 90 to 96%
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 Grating shapes for a high contrast fringe pattern as a function
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.
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
Gratings written on the Nanoruler have a very
flat wavefront when measured in Littrow
GR3 has been written with an excellent result.
The two Littrow measurements, CW and CCW, allow
the holographic component (line straightness) to be separated from substrate
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
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 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.