View Full Version : Diode Lasers

Bill George
05-01-2016, 6:27 PM
These people have some interesting products for DIY lasers > https://jtechphotonics.com/

My question, are these 445 nm diode lasers usable for etching or engraving glass? Since they are visible light, I wonder if a black or dark coating on the reverse of the glass would improve the results?

Dave Sheldrake
05-01-2016, 8:34 PM
Glass doesn't see 445nm, it will pretty much go straight through (from memory it's about 96.7% transmission)

445 is dangerous...VERY, the spot size although very poor quality is tiny giving high power density and the photon energy is comparitivly huge. The mechanics of how it *burns* is also different,Materials with a band-gap energy of under 2.788eV will undergo a photochemical process when the 445nm laser is employed (in effect a cool process) On the other hand, a CO2 10,640nm will be a 100% photothermal process, which will cause carbonisation.
There is no real direct way to compare 445 to 10,640 as such other than watt seconds (even that is a bit generic) but what it will show is watt for watt a 445 is roughly 20ish times the power of a co2. (there is so much more involved but this will do for a general understanding)

Put it this way..one european seller of 445 based systems was fined 80,000 Euro's after a kickstarter for selling diode based systems that didn't comply with safety regulations......

ps: inside carving lasers for doing glass blocks use frequency doubled green lasers (532nm) so the use of visible wavelengths is pretty common these days

pps: Credit to Vasily Basov for extended info

Bill George
05-01-2016, 9:19 PM
Dave thanks for taking time to reply. Yes if I go with the project it will be with the required safety glasses. If you coated ether the front or back of the glass object with a black paint would that allow the etching or engraving?

Dave Sheldrake
05-01-2016, 10:41 PM
A 445 will etch paint (as far as I know) but the glass will effectively be invisible to it, unless the glass absorbs some of the energy it won't change (the focal lens on a 445 is glass)...ergo it won't mark or engrave.

Quite a few companies jumping on the 445 bandwagon due to the availability of high power diodes these days at low prices (from projector systems apparently) but an equal number are being shut down by the authorities given the number of hand held diode powered *toys* being marketed. I'd expect some pretty strict enforcement on it soon given the potential for damage.

(as an aside, they have also been used in hand held format to fiddle a certain type of pay game machine so are in the spotlight anyways)