589nm misbehaving - wrong wavelength!!

[trencheel303]

I'd never thought of shining mine through the grating and observing the results this closely, I think I've got my tomorrow night sorted out!

I do distinctly remember, my 594 always or almost always lased 532. You just couldn't see it, until you split the beam.

 

[ultimatekaiser]

Hello folks, here's the image of the five dots; the first and last ones flicker on and off a lot.
Second and fourth lines are the ones it settles on.

seems alot like mine. it does the 3 yellows and occasionally will flicker 591 and 593.5 eventually, dips to 583.8 only, which then gradually phases into 586, lases there strongly for a while, then just suddenly jumps to 589 only all at once, which makes you realize just how orange it is. the 59X.X wavelengths don't really ever come in fully.

I'd never thought of shining mine through the grating and observing the results this closely, I think I've got my tomorrow night sorted out!

I do distinctly remember, my 594 always or almost always lased 532. You just couldn't see it, until you split the beam.

Try it out. if you have a good reflective lab grating then even better, as it will have lower losses.

 

[trencheel303]

I did end up testing mine, and it's rock solid stable. The wavelength doesn't appear to change at all and apart from rapid shifts between one or two modes, or even half modes, the dot doesn't even "wander" a tiny bit. My laser also prefers it cold, so a few minutes of runtime sees the output drop to more like what you'd get out of a good pen laser.

..having said that, I didn't do this from a great distance, so I might try again. It may need more distance to split lines that are close together.

 

[Sta]

seems alot like mine. it does the 3 yellows and occasionally will flicker 591 and 593.5 eventually, dips to 583.8 only, which then gradually phases into 586, lases there strongly for a while, then just suddenly jumps to 589 only all at once, which makes you realize just how orange it is. the 59X.X wavelengths don't really ever come in fully.

Interesting! Perhaps it is possible that my laser is emitting at wavelengths <589nm. :evil:

I did end up testing mine, and it's rock solid stable. The wavelength doesn't appear to change at all and apart from rapid shifts between one or two modes, or even half modes, the dot doesn't even "wander" a tiny bit. My laser also prefers it cold, so a few minutes of runtime sees the output drop to more like what you'd get out of a good pen laser.

..having said that, I didn't do this from a great distance, so I might try again. It may need more distance to split lines that are close together.

Interesting, thanks for doing that. I did mine at about 5 feet. What was the distance for yours?

 

[trencheel303]

about the same. i'll do it over the length of my hall though, which is at least 4x that.

 

[robomont]

with plasmas,as energy levels go up,the side frequencies will blend with main frequency.this may be whats happening.a scientific paper from the 50s era actually used the term,squashing of frequencies.

 

[Sta]

I caught it today doing 7 yellows and 532. I've never heard of any handheld being anywhere near as strange as this one!

 

[ultimatekaiser]

Nice. I haven't tinkered with mine too much yet. I'm thinking of making an aluminum holder for it and turning it into a kind of pseudo lab laser so I can temp control it.

 

[Sta]

A little update. I left the laser on today for a few minutes in order to test the mode hopping. Normally, after the laser shifts to the more orange line, it emits 532nm, which gradually lessens in intensity. This time, it did this as well, but after a few minutes, I saw 3 flashes of what appeared to be 561nm! It was too close to the main line to be 532, and too bright as well. Unfortunately, I don't have video, but I hope to have one soon. :beer:

 

[ultimatekaiser]

That doesn't really mean much. It just means one of the other yellow lines has 1153 participating in its lasing and it's leaking a few photons, like the 532. Theoretically it should also do a few red lines to. One of my 594s also does green and red, because it doesn't quite sum all of them into the Yellow, so they just barely start to get doubled instead- probably from the cavity length changing from temperature gradients. Could be any number of about 6 different greens.

 

[Sta]

That doesn't really mean much. It just means one of the other yellow lines has 1153 participating in its lasing and it's leaking a few photons, like the 532. Theoretically it should also do a few red lines to. One of my 594s also does green and red, because it doesn't quite sum all of them into the Yellow, so they just barely start to get doubled instead- probably from the cavity length changing from temperature gradients.

The weird thing is that it wasn't lasing any other lines, its wavelength had already stabilized. This was after ~2 minutes of running. Do your 589s do 532 as well?

 

[ultimatekaiser]

Some do. (I actually pull green from one in of my teardowns) I can use those crystals to get about 15 different lines. Just depends on the temperature, pump power, but mostly the mirrors and cavity length/shape. It's more than likely that the mirrors are just bungled up, probably from excessive heat or flaws in production like I mentioned before. They have to be very precise To do only yellow and if the cavity length is off for the mirrors are jumbled up, then you get leakage and over-generation of the fundamentals, so you get a little bit output of the other WLs. This is actually considered very bad, and is actually the reason a lot of scientific instruments have a grating in them or filters (or both) after the laser to isolate jut the wavelength desired. So often times it just looks like it's useless, but really it's just a precaution to prevent this type of thing from skewing their results.

 

[bloompyle]

Well this is certainly interesting... Considering the left-most line has a "halo" around the central spot, and they flicker, that almost tells me that your mirrors aren't matched perfectly with the divergence of the gain output. You'll find this with gas units as well, instead of all the light converging to the same point during each pass, it's all over the place, with more visible concentration in the center and edges of the spot.

Sometimes you get more light this way, simply because the alignment isn't 100% for one thing, but 99.9% for many things. Those numbers are far from exact, they're just to illustrate the point. This can cause other lines to resonate alongside your primary gain wavelength. The flickering observed is simply competition between the lines.

Then, perhaps as things heat up, the perfect distance within the cavity is created, and resonance of a single line is achieved.

This combined with wonky coatings, crystal alignment, and diode output, can cause some wacky stuff.

Fascinating.

 

[Sta]

Thanks bloompyle - very helpful! +repped.
Based on what kaiser said, could it be possible that the 5 lines in the image are 583.8/586/589/591/593.5?
If so, that would mean that the 'cold' line is 586 and the 'warm' line is 591...

 

[ultimatekaiser]

It probably does what my original one does-Running 589, then the other two yellows coming in, taking over, then switching back. I found out by accident one day when I was running it in the cold and thought it looked a bit to green. And sure enough it was running at 584 then would suddenly turn really orange, which was normal 589. As Bloom said, it's probably from cavity construction being less than stellar. Or gain being too high for the mirrors. I've been trying to get a better video of what mine does, I had one but I seem to have misplaced it.

 

[tomfire1735]

hmm no wonder why CNI have a big discount around 4 months ago on these yellow pointers and for a limited time they offers those obscure WL pointers...

*604nm dpss is available in hand held but the price tag is high...