Blu-Ray DVDs are the latest rage. They store much more data than ordinary DVDs/CDs and this is a result of the laser diode used to read/write the data. Other types of DVD burners use red or IR Laser Diodes, but Blu-Ray uses a violet laser diode (405nm peak). This is almost LW UV. The shorter wavelength allows a smaller dot, and higher density writing on the DVD.
Greenland minerals are highly reactive to even blue light - so I figured that a violet LD would be very interesting. These diodes are not available "off-the-shelf" for under $2,000.00 as the entire supply is eaten up by Sony and others.... So - as an experiment I bought the optical assembly for a Playstation 3 (spare part) and ripped the Blu-Ray laser diode out of it. This diode puts out about 10mw to 20mw of power; enough to make a very dangerous laser. I built my own electronic driver and installed everything into a case which previously housed a small red laser (And 15 LEDs - more on that later). Result - success! Amazing success....
With even this low power laser I could light up sodalite, tugtupite, calcite, fluorite, wernerite, all the uranium minerals, even Franklin calcite! The daytime glow was amazing. The theory is that I can use my laser while hiking to our favorite spots to see if any glow minerals are lurking in the shadows on our way. Without the laser I would have to unpack my gear, set up my light, get under a grill cover just to find out that nothing glows....
Given my success with the low-power diode, I decided to build a "death-ray" - 100mw of power.
It's the size of a small penlight flashlight, with a high-power laser diode, and 10 375nm UV LEDs filtered by Hoya glass. A single switch controls the laser or LEDs, and the unit is powered by one of my standard UV lamp batteries (small shirt pocket size). With the LW LEDs I can light up larger areas of longwave rocks for closer inspection without using the laser (and risking eye damage).
This diode was ripped from the latest and greatest DVD writer/burner from LG Electronics (GGW-H20L). This writer is a high-speed 6X writer, and the diode will run at 105mw - enough to burn! Following the same procedure I used to build the low-power model I ended up with a laser which will 1.) Light matches, 2.) Burn paper, 3.) Make rocks go crazy.
I set the output to about 85mw to conserve on battery, heat, and have a longer laser life. I then proceeded to run a few tests. This laser makes every longwave mineral glow like a banshee (as you would expect) but also makes some others glow that I did not expect. You can actually write your name in Franklin calcite with the "flash" typical of that calcite. I experimented with it outside and found that even under bright noontime sun minerals will exhibit a bright glow. In the dusk/nighttime hours I can easily light up rocks 250' away!!!
The pic above shows the beam in a dark room shot thru smoke. It's pretty much invisible until it hits something that is fluorescent.
Above is a piece of Greenland sodalite (against a white background paper). The laser penetrates the mineral and causes it to glow from within.
Wenerite - bright yellow fluorescence emanating from the small dot created by the laser
Argonite crystals - the laser digs into the specimen and caused it to glow from within...
The real test is how it works in daylight. The pics above were taken around noontime (bright sun). The one on the left shows an area of sodalite fluorescing under the beam. On the right the beam is focused on a non-fluorescent area of the mineral. In the pic the non-fluorescent area shows up as a violet bright spot, but this is due to the camera's sensitivity to the light. Your eye barely discerns a small dot. But the area of sodalite glows a bright orange - unmistakeably a fluorescent mineral!
So - I have a small powerful "UV light" which I can carry in my shirt pocket and pull out at a moment's notice. If I detect glow rocks then I can decide if I want to pull out my SW UV light and do some serious exploring. I have great expectations...
One cautionary note: These things are dangerous! Deadly! The light is very faint but make no mistake; as my pics shows, the beam is powerful and can easily blind a person - probably in milliseconds. Reflections from sharp crystal faces can do damage. It is not a toy.
