Did I break my laser?

[Lukesteral]

Hello, I recently bought a very very cheap collimating lens ($0.99) from China on ebay. I swapped the original lens for this to try it out and, to my surpise, it actually seemed to increase its cutting strength in wood. After about 5 seconds I noticed the laser was about half as bright as it should be and of course it can no longer cut or engrave anything.

Has anyone else tried these cheapo lenses before? Did the cheap lens break my laser, or was it just coincidence that my laser died right when I swapped lenses?

My laser is an unbranded 15w laser off ebay with an average of 6.5 watts. I bought it brand new about 10 days ago and I have not used it all that much yet.

 

[WizardG]

Was it by any chance a plastic lens? If the lens hasn't melted then it's possible the cheap lens didn't have any AR coating and reflected light may have killed your laser. Your 15 watt fleabay laser is probably an NUBM44 type diode. 6.5 watts is probably the more realistic number.

 

[Lukesteral]

Oh wow I'm really not the smartest guy. I neglected to even check if it wasn't plastic when I bought it. I just assumed they would all be glass. It was indeed plastic. But none of it melted, which is weird. Would a plastic lens reflect the light back to the laser diode?

 

[paul1598419]

Though it doesn't look melted to you, it most certainly has softened and is good for nothing now. I would get it out and replace your original glass lens in its place. Because the acrylic lenses are single element lenses they will output more power than a multi element glass lens will. You should buy an aspheric glass lens. They are single element glass lenses and can be had for $8.00 to $10.00, depending on where you get it. At greater distances the divergence of your laser will be greater, but at close to the engraving material it should be okay.

 

[Lukesteral]

Oh man, that is some useful information. I found some online, does it matter if the wavelength of the lens matches the laser? I'm looking at one but it is not the same wavelength.

 

[paul1598419]

Many of these lenses are AR coated for blue, so yes, find one that is for your laser. Anything AR coated for 405nm should work fine as they are AR coated up to 480nm. BTW, AR stands for anti-reflection. It is a coating on laser lenses to reduce or nearly eliminate reflections from the surfaces of the lens.