green dpss and radioactive marbles

[opcom]

what an odd thing to see:

setting a typical 50mW green DPSS laser so that the beam exits vertically from its aperture, I placed one of those yellowish tinted "radioactive glass" marbles on the aperture and to my surprise the beam inside the marble appeared red. They are presumably 2-3% uranium doped and glow bright green under black light.

(These marbles are sold as curiosities and have about 1.5-2x the background radiation level)

The green beam passes on through and is of course defocused somewhat but inside from top to bottom is a red line, not a green one.

The red line comes not from where the laser enters the marble at the bottom, but from where it passes through the top.

The spectrometer shows a broad emission from 570-635nm (yellow through red) with a strong line at 610nm.

The red line is much more pronounced in the more 'brownish' tinted marbles than the brighter greenish yellow ones.

Has anyone else done this experiment or does anyone have an explanation?

[Darcean]

How much mW loss did you experience through this little experiment? That's something I'm wondering.



Even then, it might be an interesting way to get at odd wavelengths if this experiment can be done multiple times, and the beam always exits the same place. You could even use a collimation lense to see if you can "re-focus" the beam back to a point.....

[opcom]

I made no other measurements.

[macona]

I have found you get the red line in a lot of different kinds of glasses, not just the uranium glass. It was very apparent in smoked glass edge on. I dont think it is the IR pump diode, but I could be wrong.

[shrad]

anyone to try this with HeNe mirrors as a cavity? DYE ring mirrors for red would also be nice to try...

[dar303]

Interesting!
I tried it on a small DPSS module just now but did not see any red. Anyone with a IR laser and a marble that care to try?

[opcom]

The laser I used supposedly has a filter against the pump. The IR output would be very small. In any case the energy is lower than that of the red. But by all means try it with some uranium glass.

[142laser]

Sounds like fluorescence in the glass with a line from some element.Cool! Glass can lase with amazing power with the right dopants.One shot, cool for 5 minutes...

[mixedgas]

Trace elements are added to clear glass to offset colors caused by impurities in the ore. The ~600 nm orange/red glow one sometimes sees in clear glasses is often Manganese, added to offset the green color resulting from iron. If the sand used in making the glass has trace iron, the glass will be verying shades of green after the melt. Manganese changes the valence of the iron ion in the glass, and cancels the red and blue adsorption. Green glass beer bottles use excess iron as the dopant.

I've seen microscope slides with so much manganese they had a red emission color if you viewed them edgewise in broadband visible light. Strongly doped magnanese glass, evidently is orange in color, is flourescent, and is just as sought after as uranium doped glass.

Other ions added to change the index of refraction or other properties of the finished glass can cause similar effects.

Example, Iron in the glass strongly adsorbs UV and re-radiates it as IR.

Is your spectrum like this from the marble?

http://webhost.bridgew.edu/cnoda/res...nyl/index.html ie the Uranyl Ion.

I learned this the hard way.
My employer refused to order quartz optics for a mid UV project. The Iron in the stock glass lenses really adsorbed the UV at 260 and below. I needed to detect 235 nm, and there was no way to get it past the first lens.


Steve