Focusing Laser Beams w/ Crystals???

I have recently talked to my good friend, Tim, in NJ (he is an engineering genius), and I mentioned my experimenting with lasers. I told him that I have been using an Aixiz module (with an acrylic lens) to focus the beams of my Blu-ray diodes, and he sounded mortified? “Why would you use acrylic when you can use crystal?!”, he said. Then he went into a scientific definition of the acrylic or glass weakening the beam and not packing it into a tight enough pattern. He suggest I go to a rock store and buy a clear crystal and buff it, or go to an antique store and buy a lead-crystal glass and use the stem of the glass to focus the beam. He says that using crystal tightens the pattern of the beam much more than acrylic, and that it is a much better material to use.

Any suggestions or thoughts? I myself do not know if this is true, and if so how big should the crystal be, should there be a certain shape, does it need to be concave or convex, etc. I am a bit skeptical and would love to hear what everybody has to say.

You could make a nice lens from a crystal. The material selected would have to have properties appropriate for 405nm. You would then need expensive precision equipment to grind and polish the crystal to optical standards. This is not done with a little hand buffing on something from a rock shop. A cylindrical lens, such as the stem of a lead-crystal wineglass, will only affect one axis, this will not focus the diode output into a beam, or a burning spot. A wineglass stem will not be ground and polished to optical standards. Stick with the acrylic until a glass lens coated for 405nm comes along.

Purchasing a lens suitable for that wavelength can be done now no waiting
http://www.edmundoptics.com/onlinecatalog/browse.cfm?categoryid=1105

billg519 said:

You could make a nice lens from a crystal. The material selected would have to have properties appropriate for 405nm. You would then need expensive precision equipment to grind and polish the crystal to optical standards. This is not done with a little hand buffing on something from a rock shop. A cylindrical lens, such as the stem of a lead-crystal wineglass, will only affect one axis, this will not focus the diode output into a beam, or a burning spot. A wineglass stem will not be ground and polished to optical standards. Stick with the acrylic until a glass lens coated for 405nm comes along.

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Ah… this sounds tricky. I think I won’t use crystals for anything other than experimentation with the laser beams. An I will stick with acrylic for now. Thanks for the explanation!

steve001 said:

Purchasing a lens suitable for that wavelength can be done now no waiting
http://www.edmundoptics.com/onlinecatalog/browse.cfm?categoryid=1105

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Ahhh. Thanks for the link to the website. I have 2 problems with what is on the website though…
- the “design wavelength” for all of the UV lenses is around 588 nm... My laser diode runs at around 405nm.
- They are quite expensive!

I think I shall just stick with acrylic for now : )

Thanks though.

Give Edmund a toll free call and ask for a free catalog. The catalog will provide charts on these lenses and AR coated glass lenses showing how much light is transmitted

steve001 said:

Give Edmund a toll free call and ask for a free catalog. The catalog will provide charts on these lenses and AR coated glass lenses showing how much light is transmitted

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Alright. Thanks again.

What your friend probably meant is that by optical standards , acrylic is cr@p and would not normaly be used for this.The answer you should've given him is "because it's really cheap, available, and not coated as opposed to the cheap and available glass lens that is coated for the other side of the spectrum" :

The aixiz acrylic lenses that we use aren't really better , they're just not as bad Still bad though...

Btw, wine glasses are not crystals.

Switch said:

What your friend probably meant is that by optical standards , acrylic is cr@p and would not normaly be used for this.The answer you should've given him is "because it's really cheap, available, and not coated as opposed to the cheap and available glass lens that is coated for the other side of the spectrum" :

The aixiz acrylic lenses that we use aren't really better , they're just not as bad Still bad though...

Btw, wine glasses are not crystals.

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Ahh. I will give him that answer next time I talk to him. I am actually planning on buying an AR lens for the Aixiz module that is designed for 405nm. According to the guy who sells it, that should add around 20% more power to my beam.

And yes, you are right, , most wine/champagne glasses are not crystal, but it is pretty easy to define the difference between a crystal and glass champagne-glass by just tapping both of them and listening to the tone. The crystal glass should have a much “smoother” tone.

I don't know how they make wine glasses but in the technical sense, "glass" and "crystal" are opposites. I have no idea what "crystal-glass" can mean, it makes as much sense to me as a round square. ;D

pianoman2011 said:

[quote author=Switch link=1234369448/0#7 date=1234788675]What your friend probably meant is that by optical standards , acrylic is cr@p and would not normaly be used for this.The answer you should've given him is "because it's really cheap, available, and not coated as opposed to the cheap and available glass lens that is coated for the other side of the spectrum" :

The aixiz acrylic lenses that we use aren't really better , they're just not as bad Still bad though...

Btw, wine glasses are not crystals.

Click to expand...

Ahh. I will give him that answer next time I talk to him. I am actually planning on buying an AR lens for the Aixiz module that is designed for 405nm. According to the guy who sells it, that should add around 20% more power to my beam.

And yes, you are right, , most wine/champagne glasses are not crystal, but it is pretty easy to define the difference between a crystal and glass champagne-glass by just tapping both of them and listening to the tone. The crystal glass should have a much “smoother” tone.
[/quote]

Yes, that will tell you the difference between "glass" and "crystal", but "crystal stemware" is still a glass. "Crystal" is the popular term for leaded-glass, and is therefore a huge misnomer. The lead added to the glass increases the index of refraction, and also increases the dispersion, making "crystal" glasses prettier, because they refract differently from other glass. But a piece of stemware that is called "crystal" is still a glass, it still has no long-range order, so it is not a crystal in the scientific sense of the word.

pullbangdead said:

Yes, that will tell you the difference between "glass" and "crystal", but "crystal stemware" is still a glass. "Crystal" is the popular term for leaded-glass, and is therefore a huge misnomer. The lead added to the glass increases the index of refraction, and also increases the dispersion, making "crystal" glasses prettier, because they refract differently from other glass. But a piece of stemware that is called "crystal" is still a glass, it still has no long-range order, so it is not a crystal in the scientific sense of the word.

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Oh so if I were to want real “crystal” I would have to buy one from a rock shop or something. Or go mining. So does leaded-glass, if cut and polished to lens quality, focus more efficiently than normal glass or acrylic?

pianoman2011 said:

[quote author=pullbangdead link=1234369448/0#10 date=1235080342]

Yes, that will tell you the difference between "glass" and "crystal", but "crystal stemware" is still a glass.  "Crystal" is the popular term for leaded-glass, and is therefore a huge misnomer.  The lead added to the glass increases the index of refraction, and also increases the dispersion, making "crystal" glasses prettier, because they refract differently from other glass.  But a piece of stemware that is called "crystal" is still a glass, it still has no long-range order, so it is not a crystal in the scientific sense of the word.  

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Oh so if I were to want real “crystal” I would have to buy one from a rock shop or something. Or go mining. So does leaded-glass, if cut and polished to lens quality, focus more efficiently than normal glass or acrylic?
[/quote]
I'd say no

You have to keep in mind here that we are using 10$ laser diodes. I personally would rather not spend 4-5x the cost of the laser on optics that might give a 10-20% power boost.

691175002 said:

You have to keep in mind here that we are using 10$ laser diodes.  I personally would rather not spend 4-5x the cost of the laser on optics that might give a 10-20% power boost.

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Haha that's true. But if I make some money off of my lasers, I might invest in one or two for the increasingly more expensive diodes that I will probably buy.

And the PHR-803T diode could be boosted to the power of a $200+ 6x Burner Blu-Ray diode using a normal lens. So spending not more than $100 on the lens would be worth it for me.

pianoman2011 said:

[quote author=691175002 link=1234369448/0#13 date=1235274365]You have to keep in mind here that we are using 10$ laser diodes.  I personally would rather not spend 4-5x the cost of the laser on optics that might give a 10-20% power boost.

Click to expand...

Haha that's true. But if I make some money off of my lasers, I might invest in one or two for the increasingly more expensive diodes that I will probably buy.

And the PHR-803T diode could be boosted to the power of a $200+ 6x Burner Blu-Ray diode using a normal lens. So spending not more than $100 on the lens would be worth it for me.[/quote]
The 6X is now only $60 as a sled only...