Can anyone recommend a method for cleaning a laser diode
window? I have a 35 mw diode that has a few specks of dust
on the window. I get some rings on the beam with out the
lens in place. I believe the Mitsubishi 35 mw can operate
without the lens. Well I hope so anyway. I have tried
to clean it using a q-tip and alcohol but I can only
change the dust pattern. Make it better or worse but not
make it perfect. I have a spare diode but I would like to
clean this one. If for nothing else but for the experience
I use the Mitsubishi diode without a lens all of the time so don't worry.
It took me many tries to clean a window but now I have succeeded I can do it in no time. I take a cosmetics sponge, available from any drug store, and cut of a small wedge shaped piece. soak it in alcohol and spin it across the window. It will take some practice to get the shape and size of the sponge just right as well as finding the proper amount of alcohol. I usually do it with the diode on but this is an eye hazard so be careful. You will see the alcohol evaporate off the window. After the first 50 tries it is not too hard.
There are more esoteric ways of cleaning a laser diode window but the sponge and good clean alcohol works pretty well for home. Everclean is a good substitute is you can't find lab grade ethanol. There are some lab "alcohols" that contain misc stuff ( they're just for degreasing,etc ) that can make matters worse. Getting the smutz out from around the rim has always been my headache but it's usually out of the beam aperture. Due to the power density at the point of exit on the window, diode lasers actually attract dust,etc.. via photophoresis ( optically induced static cling ).
So then the idea being that most particles which adhere to laser diode lenses are organic compounds? I understand that the specific turbulence of a particle in a laminar flow induces a greater Reynolds number at resistance surfaces such as curves but it seems to me that in a turbulent flow a particle would have to be very tiny and/or almost transparent in order for photophoresis to induce a slow climb towards deposition on the surface at hand?! The idea that photophoresis is a form of 'static cling' is not quite right is it? I would think of it more as an induced effect based more on thermophoresis in front of a laser diode then as a capacitive effect based on the electromagnetic radiation itself?! Being that the climb is not vertical through the atmosphere, like soot does, its not graviphoresis based on air densities either??! Well, either way, it would have to be smaller then a wavelength for diffraction propulsion or fairly transparent for a differentially focused beam energy gradient propulsion to have much of an effect. I would suppose that air moving past the lens stripping ions or the buffing of the lens during cleaning, or static charges traveling along the metal fittings or.... would have a much larger overall effect for attracting particles that would subsequently deposit then photophoresis per se?!
My suggestion is this.....
Put on gloves to make sure alpha particles (which are bound to a protective polymer coating or pressed onto a thin metal foil) of a Polonium isotope does not contaminate your hands. This is since what I am going to suggest is not the recommended way to handle such products.
Get one of those antistatic brushes with the built in radiation source sold at photo supply stores. The small type used for cleaning the dust off of 35mm film is a good bargain. Break away the plastic handle and the bristle assembly. The light metallic looking flat bar inside is your target. Using a fine drill of about 1/8" or smaller....drill a hole in it towards one end. Using a tin snips cut a square off which has the drilled hole in about the center of it., forming kind of a square ‘washer’. Using double stick tape with a slightly larger hole then the one drilled, attach the little metal ‘washer’ to the front of the laser diode, centered so as not to create aperture effects as the laser beam travels through it. This should seriously negate most effects which would normally lead to contamination of the front lens of the laser diode. When wishing to clean the lens again, a slight wedging under the tape with an exacto knife will pop off your ‘isotope anti-stat washer’ and after cleaning it, the washer can be attached again with new tape.
I have tried