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ArcticMyst Security by Avery

Strange crystal for blu-ray

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Jun 5, 2008
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Hi to all!!
I have found in a old lamp-holder crystal, and I have take it to put with all my laser stuff.
I have tested it with some laser, and some wavelength, but when I have shine my blu-ray in it, I have seen a cool green-violet beam inside the crystal. It seems to have a special features for 405 nm.
What do you think about?
 

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That is an interesting color, it must have some chemical element in it. It looks like a weak uranium marble.
 

diachi

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Lots of crystals fluoresce under 405nm light, much like everything else does. thats a nice crystal you have there though :) Glass also fluoresces under green laser light, you can use that to tell the difference between glass and crystal as crystal does not fluoresce under 532nm.

-Adam
 

daguin

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Diachi said:
Lots of crystals fluoresce under 405nm light, much like everything else does. thats a nice crystal you have there though  :) Glass also fluoresces under green laser light, you can use that to tell the difference between glass and crystal as crystal does not fluoresce under 532nm.

-Adam


Glass is a "borosilicate" (boron & silicon).  The boron in the glass mixture fluoresces weakly

Here is the same violet beam passing through both a glass sphere and a quartz crystal sphere

spheres1.jpg

spheres2.jpg


Notice that when the beam passes through the quartz it remains violet, but when passing through the glass it turns greenish

Peace,
dave
 
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Wow. It's a very cool trick to see if a thing is made by common glass or no. :)
 
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I find it difficult to find something that doesn't fluoresce under 405nm light to a greater or lesser degree. If you hold a diffraction grating to your eye and walk around, just about everything will give off more than violet light.
 

Switch

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I know ordinary glass actually has an amorphous structure.I'm not sure how ordinary borosilicate is, or if it crystalizes or not though.I'm not sure how many types of glass are there that are more or less commonly used.Many of them fluoresce under 532nm too. :p
 
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All glasses have amorphous structure, and varying degrees of crystallization from their ingredients and/or their processing.  Very few glasses are pure silica, because that would make it very hard to process (this can be done, it's called fused quartz: it's still a glass (whereas quartz is crystalline silica), but it's much higher quality because it's much more pure).  The names for all these things are terrible because of history and such, but basically everything out there that is glass is silica with other stuff added to it (unless it's fused quartz, but you'd know if it was). And it's all amorphous, but with slightly varying degrees of crystallinity: The order will only extend slightly beyond nearest-neighbors.

To make glass melt easier for processing or to make it better for certain properties, other things are added, like boron for borosilicate glass (aka Pyrex), or soda and lime, for soda-lime-silicate glass, the most common glass out there (like most drinking glasses and windows).  "Crystal", that really expensive glassware everyone loves, it's actually just glass with extra lead added to it:  It's still glass, but the lead increases the index of refraction, and makes it shinier (so the name "crystal" is the worst name ever, continuing the misleading name trend).  

Many of the things added to glass to make its properties better can fluoresce, like the boron or other things.  They add all kinds of stuff to glass to get it to flow right or to "solidify" right.  Glass is crazy stuff with how it works and has to be processed.  Metallic glasses are just as interesting, but with some amazing properties that are only just starting to come out.  There's still SO much to learn about how amorphous solids behave, we're just beginning to understand them.  It also hurts that cause that there are still so many misconceptions about glass out there (ie, I bet some people on this thread still believe that glass "flows", and that this results in the windows in old buildings "flowing" and getting thicker at the bottom than at the top.  Hopefully no one here still believes that.)
 
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Nice post Pulldangdead. Fe is another additive which is added to glass to make it absorb in the IR (~1um). Otherwise the absorption edge is really far out into the IR (5um or so).
 




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