Green Diode not only emitting green

It's just acting as a filter.

I didn't see anything with my diffraction grating, though i'm not leaving a pictureless update:



589nm on left, orange on right.

Meatball asked me to pop in from PL

Ok, as I see it, and from looking at the color.

Guess 1:

You have a Iodine or Bromine compound in the lamp. Focused green light into some forms of iodine compounds or pure Iodine vapor results in a orange flourescense. We use this as a spectral reference in the lab, and if you pump it hard enough with green, Iodine vapor lases weakly in the orange. Iodine or Bromine doped oils would have a much higher density and some pretty toxic stuff was rumored to be in older Lava lamps. You'll have a focal spot near the edge of the lava lamp.

Guess 2: There is a second bandgap in the diode in the orange. Its not unheard of for diodes to emit small amounts of other colors, usually much longer in wavelength then the design emission. Usually not as coherent light, though.

Guess 3. The dye or other material in the lamp is wavelength shifter, ie flourescent or Raman, or some other Stokes shift, or it acts as a filter. If the dye has a tight adsorption band edge, 532 might not hit it hard enough.

This is not uncommon:

I have a blue led with some small amounts of green and near UV and a older high brightness green led with a orange side band. You can have some spontaneous emission in the orange as a side effect of the doping in the diode.


First of all, I dont know how financially well off you are to be messing with a 520 green. If you feel comfortable with your driver, drop the laser to just below lasing threshold and see if the orange is there. If it is, well, green laser diodes have non coherent orange emission and a secondary bandgap.

In the unlikely event of lasing in the orange, well, no suprise. The green bandgap energy would be much higher then a orange, so wierd things can happen based on the structure of the diode. I doubt its a single layer junction, anyways. So who knows what the other layers are doped for.

If that does not solve the issue, well, most plastic gratings are poor spectroscopic devices. You need to find a proper monochromator, and Ebay has forced the price of those through the roof. I usually use two Littrow prisms in series for lasers. The common 60 degree prisms have really poor dispersion for laser work.

Where are you located at? I may know some one in the area who does spectroscopy and who can run this to ground. I will ask our local 520 nm owner to take one to where he works and have a friend of mine take a look.

If he does not wish to do so, I can always loan you a pair of Littrows, but I would prefer to do it the proper way with a spectrometer.

Some one could always email Osram and ask what the stray light from this beast is.

I'll keep a eye on this thread.

Steve

aryntha said:

(Now, i've been gone for a bit; if there's gonna be another GB on these PL520s..... i'm there...)

Click to expand...

Osram PL520 Green Laser diode GB feeler Any interested out there. - Page 2

I'll update the OP, but it's not specific to the lava lamp.

I don't think that these iodine doped oils are in them, it's dyed myself with McCormick brand liquid dyes in distilled water and sea salt (unless the sea salt contains enough iodine and somehow makes oil-- still this effect isn't specific to the lava lamp.)

I'm not really going to mess with the current on this, I got it in a GB and can't really be pushing one of these cause I don't want to buy another one.

I'm in eastern central PA, and I'm also already sending it to MarioMaster monday morning, he's not far from me at all and has a spectro.

I never actually thought to email osram, going to check that out after I post this.

Dr. Sam Goldwasser is in Philly,
He can run this to ground in minutes.

Steve

OMG thats the guy who does the Sam's Laser FAQ!

Well, this is an interesting effect, though I have seen it while using 532nm DPSS when shining the beam through standard acrylic rounds, or
even soda glass.

I'm no expert on photonics, but I am guessing that by passing green laser light through some materials shifts the wavelength up slightly to produce a yellow/orange secondary emission??? :undecided:

I don't think so, Seoul. Shifting the wavelength isn't that easy, methinks.

Wolfman29 said:

I don't think so, Seoul. Shifting the wavelength isn't that easy, methinks.

Click to expand...

Well, you may be completely correct on that fact, but many other people have had a similar occurrence with DPSS up-shifting towards Orange when passing especially through Acrylic or even through various Alcohols.
Makes me wonder if certain organic molecules absorb green laser light.
:undecided:..... However, in the case of the green diode it seems that the an orange laser emission has been produced. Secondary emission? :wtf:
Then I thought about it a little more and, since this is a lava lamp.
the dyes in the bubble material perhaps become excited by 510-520nm laser light???

4-(dicyanomethylidene)-2-tert-butyl-6-(2-(1-(4-tert-butylphenyl)-1,2,3,4-tetrahydroquinolin-6-yl)vinyl)-4H-pyran (OJ1)

and 4-(dicyanomethylidene)-2-tert-butyl-6-(2-(1-(4-tert-butylphenyl)-2,3-dihydro-2-methylindolin-5-yl)vinyl)-4H-pyran (OJ2)

both are used in the production of red/pink florescent pigments, both can be used as laser dyes or dyes for OLEDs. :thinking::thinking::thinking::thinking::undecided:

Well, the DPSS up-shifting is possible because of the impurities in the doubler - it may be doing both SFG and SHG.

But the dye possibility... wasn't that discounted?

Why would it be doing SFG AND SHG? It seems like it wouldn't make sense.

Asides from that, this is a diode laser, not DPSS, so ... that wouldn't work, right?

Well, impurities in the crystal could easily cause SHG and a tid bit of SFG, and considering the crystals are cheaply made, that may very well occur.

However, it can't happen here because this is a diode ^_^

An orange sideband doesn't have to lase to appear as a "dot," but the dot will be less defined than the green. After all, a diode below lasing threshold still makes a dot. I know many (all?) 405nm diodes have a tiny emission in the yellow and some other areas. Putting it through a diffraction grating is the easiest way to check this out; I've found a couple "multiline" greens this way.

Let's see if I can finally post some of these pictures:

Quote:
Originally Posted by Cyparagon
An orange sideband doesn't have to lase to appear as a "dot," but the dot will be less defined than the green. After all, a diode below lasing threshold still makes a dot. I know many (all?) 405nm diodes have a tiny emission in the yellow and some other areas. Putting it through a diffraction grating is the easiest way to check this out; I've found a couple "multiline" greens this way.

That seems to be the case here. Just got done doing a few rounds of testing and it appears that the stray orange light ZRaffleticket was seeing is just some extra light emission from the die, it doesn't appear to be coherent.

Let's take a look at some benchmarks first-
Typical 532nm DPSS:


514nm Argon Ion laser line:


And now ZRaffleticket's 520nm handheld:

Looks like the laser peaks right at 517.5nm according to my spectrometer.

Let's zoom out a bit:

There are indeed some little bumps out there in the longer wavelengths

I amplified these readings by shining the laser through my green blocking goggles - this reduced the main green output by several orders of magnitude while still allowing the longer wavelengths to pass fairly easily:

There we go, that appears to be the emission ZRaffleticket was seeing through his lava lamp.

I was unable to separate any significant amount of orange light using a conventional diffraction grating even when filtering out most of the green.

I have to say this laser is pretty sweet though, to my eyes there is no question that it's a different color to 532nm, very close to the argon ion line that I'm a fan of.

wow nice bumps!

Nice to know I'm not crazy, thanks for doing this :beer: