Blu-Ray 6x plus UVA LEDs fluorescense

[chimo]

What's nice about this wavelength is that it seems to focus to a really small dot and that many materials seem to absorb much of the energy rather than reflect it. This translates into great burning ability. I burned a line onto a piece of bare SPF 2x4 with an output of ~70mW. The wood started smoking almost immediately.

 

[Switch]

LEDs have a peak wavelength. The filter blocks the rest.
Purple on the other hand is a mix of blue and red wavelengths.

I'm sorry but my mind doesn't seem to make a difference between purple and violet ;D

So, anyway, the peak wavelength of these LEDs is about 395 nm then? So from what I can tell, that's still slightly visible, so it still escapes the filter....so you can't have fluorescence without the violet glow? :'((using one of the standard LEDs...)

 

[Pirateo40]

So, anyway, the peak wavelength of these LEDs is about 395 nm then? So from what I can tell, that's still slightly visible, so it still escapes the filter....so you can't have fluorescence without the violet glow? :'((using one of the standard LEDs...)

Not sure what filter y'all are talking about.  My filter on my unit is a UV pass filter - but ONLY for the LEDs.  The LD passes out the hole in the middle.  TO my knowledge there is no filter inside the diode (other than a window with anit-reflective coating).

These laser diodes put out 405nm peak, and a range of 400nm to 415nm.  This is at the very far end of the visible spectrum, but still visible.  Below 400nm we are talking UV - invisible.  400nm is the cutoff for visible/invisible light - but some people have a hard time seeing this far-end purple and see mostly blue.   Fluorescense is caused by short wavelengths - often the shorter the better.  Many things are fluorescent under 450nm - ruby is a great example.  That's why they use lights with a bluish cast in jewelry shops - their rocks just look better.

But - many more things will be fluorescent only under pure UV - very short wavelengths - 350nm (longwave UV), 302nm (Midwave UV), 254nm (shortwave UV) for example.  This light is invisible.  But the glow will be very bright from many minerals.

The reason this violet LD causes certain rocks to glow orange, yellow or green (or marbles with uranium) is that these specific items are sensitive to the 405nm wavelenght and emit their own glow, but you can still see the violet light from the laser....

A side note: blacklight bulbs (Halloween) put out LW UV - around 365nm.  But you still see visible light (blue/purple) but that's only about 20% of the lamp's output - the rest is invisble UV.  Very hard to get pure UV.  LW is also what we get from the sun (along with a little midwave (UVB) - UVA + UVB causes tanning).  SW does not reach us as it is blocked by the ozone layer....  Anything under 350nm is very dangerous for your eyes and skin - even 350nm might not be very good to stare into.

Mark

 

[FireMyLaser]

[quote author=FireMyLaser link=1205712345/30#31 date=1205849949]LEDs have a peak wavelength. The filter blocks the rest.
Purple on the other hand is a mix of blue and red wavelengths.

I'm sorry but my mind doesn't seem to make a difference between purple and violet ;D

So, anyway, the peak wavelength of these LEDs is about 395 nm then? So from what I can tell, that's still slightly visible, so it still escapes the filter....so you can't have fluorescence without the violet glow? :'((using one of the standard LEDs...)[/quote]
The 395nm LEDs have a pretty clean output and is visible. It does have other wavelengths that is over 395nm aswell, but in very small porportions. There is no invisible UV, or very, very little  :'(. IMO the filter is not needed. You might have better luck with 385mn, but they are not as clean as  the 395mn ones. The light looks kinda violet-white, so the filter would do better with those. If it works that is.        

Sorry for the off-topic  :-[ Love the laser btw

 

[Switch]

Yea, I wasn't talking about the laser diode,(but still, this emits more linesof diferent wavelengths? :-?).I was goind on about the LEDs, the 395nm is pretty visible anyway, so why do you need the filtering glass?

 

[FireMyLaser]

To eliminate the all the higher wavelengts that don't make materials fluorescence. This makes finding fluoresent materials more easy. Do you watch CSI? That orange filter is a smart thing too.

 

[Pirateo40]

Yea, I wasn't talking about the laser diode,(but still, this emits more linesof diferent wavelengths? :-?).I was goind on about the LEDs, the 395nm is pretty visible anyway, so why do you need the filtering glass?

Any wavelength under 400nm is supposed to be invisible.  In a perfect world this would be true - but alas, we live in a unperfect world.  *All* UV LEDs output light in the visible spectrum - that's the dull violet glow you see.  If it were pure 395nm (and of course below) you would not see any light.  I have a 255nm shortwave LED (lotsa $$$), it's very weak 50uw but still puts out a significant amount of visible light.

The filter is a very special glass which transmits UV from 254nm to 400nm, and blocks 90% of light above 400nm.  It's called a UV pass filter.  UV light is generated normally by low-pressure mercury fluorescent tubes (the kind in your kitchen).  The white tubes are really a result of phosphors on the inside of the tube generating light from the SW UV (254nm) inside the tube.  Depending on what kind of phosphor you use you will get different wavelengths.  A BLB (blacklight bulb) is coated with 365nm phosphor - but it still looks white (bluish white).  The "Filter" eliminates the white light and passes mostly UV (sometimes they incorporate the filter directly into the bulb - your "blacklight").  An uncoated bulb (germicidal) outputs 254nm UV (Shortwave) from the clear "glass" (Acutally quartz) AND a lot of bluish/white light.   This special filter passed the UV and blocks the white light....  (But it must be a very special filter material, as ordinary glass will not pass the shorter UV wavelengths - it's called Hoya glass).

I have a pretty good explantion of this on my web site for those interested: http://www.minershop.com/html/uv_light.html

Confused????  Off topic - but - this is my field, and happy to impart knowledge as y'all have done for me in the world of lasers....

Mark

(BTW - we use the filter to eliminate all the visible light we can, as it is objectionable to our hobby, and makes it hard to identify minerals, see pure fluorescence, etc.  The blue cast is artificial light - we only want to see the FL response of the minerals.)

 

[Pirateo40]

Just as an example of fliter LEDs - this is a pic I took of sodalite under the UV LEDs in my Laser assy. The background is a piece of white paper (also fluorescent) thus you see the blue glow from the paper. But note how the rock is a nice pure orange (compared to the photo earlier in this thread with the laser)

Mark

 

[Pirateo40]

Same rock litup by the laser. This laser is so trong that it makes the sodalite glow a vivid orange, but you can see the violet spill-over onto the non-fluorescent areas of the rock, as well as the paper.

 

[Pirateo40]

One final pic showing the power difference between the PS3 diode and the LG 6X diode.  This was taken with both of my lasers directed onto a piece of calcite.  The calcite glows a reddish orange color under UV.  

The dot to the right (small, blue) is the laser with the PS3 diode.  The bright dot on the left is the 6x diode.

I don't have the equipment to measure mw, but the PS3 diode is running at 38ma, and the 6x about 85ma.  But it's obvious from the pic how much brighter the 6x is compared to the PS3.

I wonder if standard measuring equipment can accurately measure the wattage of lasers operating at these short wavelengths????

 

[Hemlock_Mike]

Mark --
My PS3 puts out ~11 mW at 38 mA. The 6x should be ~60 mW at 85 mA.
Look on Ebay for power meters. Ask here before you buy -- Theres all different kinds and those $20 ones are useless.
Where do you get the neat rocks? I looked all over my wife's rock garden last summer and only found sex stones ;D Some of yours look like fire.

Mike

 

[Switch]

Well it's not that off-topic, we were still discussing about your unit. :So yes, I see where I made the confusion, I thought the violet light I see is 395nm.I was actually looking for a way to do what you did.Where can I get such a filter?And how much would it set me back.I'm planning on buying the 20 UV LED pack from DX and making a huge fluorescence flashlight, and such a filter would make it a whole lot better.But I am expecting that the filter alone is going to cost me more than the LEDs and the flashlight host Could we continue this in PMs so not to go even more offtopic? :-/

 

[Pirateo40]

Hey Switch

Not off-topic for me - glad to discuss.... The Hoya glass is only available (new) from Hoya, and much like our diodes, they don't want to deal with the end-user, and they charge an arm/leg. It costs about $4/sq in and of course is available in large sheets.

How big a piece do you need? I have plenty here (I also build UV lights) and can ship a piece off to you if it's not too big... The biggest problem is gonna be cutting it. I use a diamond bladed saw, and then round it up on a jeweler's cabochon wheel... (diamond polishing).

Mike - the rocks are found all over the place. I specialize in rocks from Greenland, but you can find them everywhere.... Franklin NJ is a hot spot, areas in AZ, IL, CA, NC, and many others....

Mark

 

[Pirateo40]

Just thought of a neat accessory for Blu-Ray lasers - Franklin calcite. The laser is so powerful that you can "draw" on the rock with it. It leaves tracks of your lines as you move (actually phosphorescense). It's cheap - you can pick it up in Franklin NJ for $1/LB. Or find some cheap on ebay in the fluoresent mineral section.

These lasers do neat things with many different minerals: sodalite, calcite (some), wernerite, ruby, autunite and andersonite (uranium), fluorite, and many more. The more translucent the mineral the deeper the beam "digs" in causing a glow to appear from within....

Just a suggestion for another thing to show off your lasers.....

Mark

 

[Switch]

Wow, I didn't know there were phosphorescent stones ;D

 

[Hemlock_Mike]

Mark --

I'm getting PO'ed now  ;D  I got my 6x going again and no rocks here  Just snow ......  You have a neat hobby and now combined with lasers ---
Double good fun.

Mike