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          Fluid Jet Polishing

Fluid Jet PolishingFluid jet polishing is turning the world of optical fabrication upside down. LightMachinery can routinely create near perfect optical components using this cost effective, computer controlled technique.

Fluid jet polishing is an enabling technology that enables LightMachinery to tackle some very complex and difficult optical fabrication tasks with confidence. The ability to adjust the shape and flatness of components with very thin aspect ratios has allowed LightMachinery to fabricate very uniform thin etalons and wafers. The ability to measure the final performance of complex assemblies such as Michelson Interferometers and then to make arbitrary surface corrections to these components is opening up a new era of astronomical device manufacture. Contact us to discuss your requirements

Fluid Jet Technology
LightMachinery's patented fluid jet polishing system uses a fine stream of slurry to accurately remove nanometers of material. Fluid jet polishing is a type of computer controlled polishing that has been refined by LightMachinery. The process is simple;

Step 1 Measure the current surface profile, this is usually done using an interferometer
Step 2 Compare the current surface to the target surface profile
Step 3 Compute the required removal patern

3 Simple Steps to Perfect Surfaces

The resulting surfaces can be polished to within a few nanometers of the target shape. The following section on applications shows the wide variety of applications for fluid jet polishing; corrected flat surfaces, making aspheric lenses, ultra-uniform thickness substrates and etalons, unusual shapes and corrected accumulated errors in large optical assemblies.

Applications and Capability

Ultra Low Transmitted Wave Front Error Created for the Photonics West trade Show this 4" diameter piece features a large axicon, an array of lenses, a cylindrical lens, a powell lens and a fish. The piece was then optically contacted to a flat surface so that interference fringes are visible in the air gap.
Ultra Low Transmitted Wave Front Error A conventionally polished 2" x 2" fused silica substrate (before fluid jet polishing)
Measured with tunable laser mapping system in transmission there is a peak to valley slope of about 115nm
Ultra Low Transmitted Wave Front Error This same substrate after FJP
Measured again with tunable laser mapping system in transmission there is a peak to valley error of about 3nm. Shown here in the same scale as above
Ultra Low Transmitted Wave Front Error Another 2" x 2" fused silica square
This substrate was measured in reflection using a Zygo interferometer, the error is very large, about 1.8um of concave shape
Ultra Low Transmitted Wave Front Error After FJP
Shown here at the same scale as the picture above the error is 10nm peak to valley
Ultra Low Transmitted Wave Front Error A Very Flat 4" Silicon Mirror
Measured with a Zygo GPI after fluid jet polishing this silicon mirror has a surface variation matched to the zygo test flat to 1/100 wave peak to valley over a 95% clear aperture
Ultra Low Transmitted Wave Front Error Note the rms surface figure of lambda/1000!
This is important for creating high finesse etalons
Ultra Low Transmitted Wave Front Error This before and after fluid jet polishing
interferogram clearly demonstrates the FJP's ability to correct transmitted wavefront errors. This process was completed in a single pass, processing on only one side, based on transmitted wavefront data from a Zygo interferometer.
Micro Lens Array This is the resulting interferogram from fluid jet polishing a grid of 3 x 3 micro lenses into the surface of a piece of fused silica.
Micro Lens Array Essentially these are 2D sine waves so there are 9 positive lenses and 4 negative lenses on the surface
Micro Lens Array corss section The amplitude variation (sag) of the lenses is about 500nm over about 3mm but the radius of curvatures in the central regions of the lenses are about 120cm.
micro lens array optically contacted The micro lens array optically contact to a fused silica flat in order to make the interferogram visible in fluorescent light.
aspheric cylindrical lenses - powell lenses Aspheric cylinderical lenses, acylinders, are useful in laser beam shaping applications and have become a bit of a specialty at LightMachinery. Designs such as the Powell lens can create a line focus with uniform intensity over long distances. Our unique fluid jet polishing capability makes polishing acylinders a routine process.
axicon profile Axicons are optical components that are shaped like cones. They are not simple to make usign conventional polishing technology but the fluid jet system seems to have no problem. This one has a 3mrad slope and is designed to flatten the top of a gaussian beam
germanium axicon The interferogram from this germanium axicon has equally spaced fringes because the slope is constant. Axicons are normally used to change a focused spot into a focused ring. In this case it will simply make the CO2 laser beam a little more 'top hat' than gaussian.
Target File Target surface
A simple .jpg, 256 x 256 of ISO (we are still very pleased about our ISO 9001 certification). The depth was set to 250nm for the text.
FJP starting surface Starting Surface
This was already a pretty good surface, polished my our opticians to about 1/8 wave over the 2" x 2" square
After FJP After Fluid Jet Polishing
This beautiful pattern was made using the fluid jet polishing machine in the usual raster mode.
Optically contacted Fluid jet polishing surface After Fluid Jet Polishing
The ISO image is polished (backwards) into the square optical component that has then been optically contacted to the lower 3" diameter holder. The visible fringes are from the air space between the surfaces.
Optically contacted Fluid jet polishing surface Fluid Jet Polished
And then Adhesive Free Bonded (optically contacted)
Target File Target surface
Another simple .jpg, 256 x 256. A constant change in color value between each segment.
Zygo Measurement of the Etalon Array After Fluid Jet Polishing
A stepped depth that gives rise to a phase mask matrix
Optically contacted air spaced etalon array Air Spaced Etalon Matrix
This piece was then optically contacted to a flat piece of fused silica creating an array of air spaced etalons. Each one is has a gap that is 100nm wider than its neighbor
Before FJP Conventional Flatness λ/10
Shown here a conventionally polished fused silica substrate. The wedge in the part is very good, about 50nm, less than lambda/10
After FJP

An Early FJP result - Flatness of λ/100
After processing half of the part with fluid jet polishing. The surface flatness is reduced about 6nm peak to valley or lambda/100

Surface roughness before Atomic force microscope analysis of a conventionally polished fused silica surface. The size of the area is 1.5 x 2.5 microns. Surface roughness is 1nm Rms
Surface roughness after Atomic force microscope analysis of a fluid jet polished fused silica surface. The size of the area is 1.5 x 2.5 microns. Surface roughness is 1nm Rms
Micro-channels Micro-channels and complex patterns can also be created by combining fluid jet polishing with masking. These shallow microchannels are about 20nm deep and more than 1000nm wide (the vertical axis is greatly expanded). Applications include microfluidics and optical phase masks.
A fluid jet polished image of a penny

More strange surfaces
A fluid jet polished image of a Canadian Penny in a 2" square of fused silica. The fused silica was then optically contacted to another piece of fused silica and the air space in between creates visible fringes that look a lot like an actual penny.

A fluid jet polished image of a penny A depth map of the penny image
Crossed Cylindrical lenses, fluid jet polished More strange surfaces
Another optical element that would be impossible to make using conventional polishing, crossed cylindrical lenses
Crossed Cylindrical lenses, fluid jet polished A top view of the crossed cylinders


Fluid Jet Polishing Technology
Perhaps your application is outside the world of conventional optical polishing. We are still here to help. Fluid jet polishing is capable of adjusting a very wide range of materials from metals to Silicon Carbide. Please contact us to discuss you application and we will be glad to work with you on finding a solution.

If your application requires truly flat smooth surfaces, uniform thickness or surfaces with arbitrary shapes then contact our staff to discuss your needs.

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