Scanning Electron Microscope
PGL uses an Amray Field Emission scanning electron
microscope (SEM) to analyze writing, etching and cleaning results for
gratings. The image at right shows a grating etched into a silica layer
with a multilayer below. The multilayer is composed of hafnia and silica
and extends for 26 layers (not visible in micrograph)
700 mm Fizeau Interferometer
The 700 mm interferometer is used to evaluate
the wavefront flatness of substrates, coatings, and diffraction gratings
at 633 nm and 1054 nm.
This instrument uses a spatial-carrier static
acquisition (Zygo Flashphase)method to gather data at the frame
rate of the camera. This makes the instrument virtually insensitive to
vibration. In addition FTOptics designed the TF mount to rotate the Transmission
Flat (TF) so that a full mapping of the critical reference surfaces could
be made. This method is outlined in a paper by Flemming
Tinker and Michael Brae.
PGL also has a 50 to 100 mm aperture phase-shifting
interferometer for measuring high spatial frequency features and small
Perkin-Elmer Lambda 19 Spectrophotometer
This remarkably versatile spectrophotometer
is used for everything from evaluation of complex optical coatings to
calibration of optical profilometers. Ours is linked to our network and
the results are analyzed using OptiRE reverse engineering software.
We can measure coating in atmosphere or dry nitrogen and in transmission
or at a fixed angle. Note the post it notes around the monitor. Where
would we be without Post-it notes.
PGL has two optical profilometers to measure
film thickness, etch thickness, surface roughness, curvature, and coating
stress.The instrument at right is fitted with a purge chamber to allow
the samples to be measured in a dry nitrogen atmosphere to simulate vacuum
conditions. PGL studies environmental and aging effects of stress in coatings
so that the gratings will perform without failure or excessive wavefront
deformation in vacuum.The post-it notes on the monitor cannot be seen
but, trust us, they are there.
Other instrumentation include a fiber-optic
spectrometers, several residual gas monitors, an optical microscope and
a laser-based photometer platform. This last device is moved to the Nanoruler
for mapping diffraction efficiency on the large gratings.