In Wikipedia, you can find more details about what is an Excimer and why the Excimer Laser is called so. In practice , and excimer laser is a UV laser that is used to evaporate a thin layer or material who's shape is defined by a mask. There are 2 main differences with the Epilog laser cutter:
The Excimer laser is using a lower wave lengths ( UV ) , and can therefore cut thourght metal, glass , ceramics...
The Excimer laser has one extra feature in comparison with the Epilog laser
cutter : it is using masks. Masks can be used to define the shape of the laser
beam. The good news is that the Excimer itself can make its own masks...
The model we have is situated in E15-023 ( in the Physics and Media research space). Is was purchased from Resonetics ( http://www.resonetics.com/ )
We have a RapidX-250 model from Resonetics. This model is using Fluoride, Argon,Krypton and Neon. It can either be used at 193nm or 248nm.
There is a Lamda excimer laser in the MIT Spectroscopy Laboratory and another Resonetics in the Microsystems Technology Laboratories.
WARNING : Fluoride gas is extremely dangerous. A combination of very lowd and blue light alarm with a Fluoride detector was installed. If you hear the alarm please evacuate the building as fast as possible.
A general microfabrication manual including Excimer techniques is availible here : Manual (obtained from Resonetics.com ) .
A user manual is available here . A paper version is also available by the Excimer. Please feel free to read it and add your findings to this page.
The Excimer laser is using powerfull (400mJ/square cm) UV light. One can not see the beam. It is relatively well protected. However inclosures can break and interlocks can fail. For safety reasons please don't use the Excimer laser unless you received formal training from Manu Prakash ( manup at mit dot edu ).
Here is a diagramm of how aser ablation works ( obtained from this manual : Manual ) :
The comercial laser system we aquired is commanded using it's proprietary software. You can write programs (computer assisted manufacturing) to command the laser. Here is a typicall program file :
Excimer program example : file More details about programming can be found in the user manual.
You can also use cam.py ( http://web.media.mit.edu/~neilg/fab/dist/cam.py ) , a.k.a. the inhouse developped cam tool using python to generate the Excimer "oms" file.
So far, 2 kind of problems arised :
1. Either the gas in the laser chamber was too old, and the laser power wasn't high enough to machine. The obvious solution is to refill with new gas.
2. Or the beam wasn't properly focused. In this case many different issues rised : non homogenous beam, lack of power...
General TIP : if something doesn't work as it should check the focusing !
Here is a non exhaustive list of materials from the Resonetics web site , that can be machined with the Excimer :
| BIOABSORBABLE | poly-l-lactic Acid (plla) | polycaprolactone (pcl) | polyglycolic Acid (pga) | ||||
| PLASTICS | polyethylene | nylon | polycarbonate | polyurethane | polystyrene | pmma | pet |
| CERAMICS | alumina | zirconia | pzt | silicon carbide | aluminum nitride | tungsten carbide | |
| METALS | tantalum | tungsten | nitinol | platinum | titanium | molybdenum | stainless steel |
| GLASS | fused silica | borosilicate | sapphire | diamond | ruby | quartz |
One should keep in mind that the Excimer can work at 2 different wave length , and different materials work better at different wave lengths. However to swap wave lengths, mirrors and lenses might have to be changed and this also means some realingnment is necessary.
Here are some pictures of machined parts (from Resonetics for metal and glass)
Metal :
Glass :
A short list of publications on Excimer machining of materials can be found here :
http://fab.cba.mit.edu/tools_new/machines/excimer/matdata/
http://www.resonetics.com/
Competition : http://www.lambdaphysik.com/script/content.asp?area=2&sitepages_id=93&mid=4