Why is my Stabilite 2017 AR giving me the blue line when it's set to the green?

[optonano]

The Bottom scale is the current range. You are showing 17 amps which is not much current for that laser. The tube current scale is the bottom scale. The power scale is the upper scale.. The meter has a three position switch, make sure its set to current when first aligning optics. Do not exceed 25 amps during alignment. Once its lasing you can set the meter switch back to WATTs to manually peak the mirrors for best power. Make sure the mode switch is set to CUR when aligning optics

As you tune the vertical adjust knob it rotates the prism. The prism only permits one line to lase at a time.This is called intracavity line selection, the laser can lase on the following lines:

514.5
501.7
496.5
488.0
476.5
472.7
465.8
457.9
454.5

As you tune the vertical control, the prism will select out one of the above lines for lasing, one at a time. In between each line will be darkness. If the tube current is low or the mirrors are poorly aligned, you will only get 488 and maybe 514.5. Make sure the iris is open when first finding lasing.

I'm jammed up working on my Masters tonight. Come back tomorrow and we will finish the tuning discussion. Don't move the front output coupler mirror if you have not moved it up till now.

Steve



Generally the laser will lase at 55-60% of the specified all lines power when the prism is installed.

The light pickoff is a well enclosed beam splitter at the output end of the laser , it picks off ~ 1% of the laser beam and routes it into a photodiode to drive the Wattmeter and constant light output functions of the laser.

Put the laser in constant power mode (constant light output) and set the power down to ~ 100 mW. Aim the laser at a cinder block wall or other diffuse, fireproof, surface. Make sure your eyes are one and a half meters from this diffuse surface and gently lift the goggles. You should see the true color of the beam. But keep the power below 50-100 mW until your LSO helps you determine if you have safe viewing.

Hi Steve, thanks again for all the help. So many responses! I'll try to address everything bit by bit.

Currently (no pun intended), when the laser starts, with the current knob completely down, and in current mode, and measuring current, it maintains about 10A just to have plasma (which we can see as a faint bluish glow if we open the aperture).

We always have the aperture completely open (10) when trying to find lines.

Okay, so currently we have the 488 blue line lasing fine, but we'd like to get back to the 514 line we originally had before we futzed with something and made it stop working.

Here's what I'd like to know: If we have the blue line lasing, then does that mean to find the other lines, assuming the power is high enough, we would only need to adjust the vertical knob? (as in, because we have some line lasing, that means the horizontal knob must be tuned well enough?) Or could we also still have to adjust the horizontal knob too? That would be a good thing to know.

We've found that by cranking the current up to about 40A, we can get the output (at totally open aperture) to get to about 1W, which isn't too far off from the max of 1.5W for the 488 line.

thanks!

[optonano]

You could remove prism and put in full reflective mirror and get all lines. I have seen the Brewster windows get cloudy and cause power loss. You can adjust these lasers at full current, best way to get back in alignment then decrease to tune fine. Clean all optics with reagent grade acetone to get off oils the clean with alcohol 90% or better 5 or 6 times to remove water solubles. Go back over optic with clean dry q tip wooden handle type, plastic ones melt in acetone an ruin optics. I have seen a laser go from 1 Watt to almost 5 Watts with this method. Takes extreme patients. I also walk front and rear reflectors cw and then ccw with both hands to get peak output but dont go to the point of loosing beam. I have spent hours after changing optics getting a beam back, if its real bad I use a red laser to align front mirror, then rock vertical on rear mirror while cw and ccw to get laser to flicker.

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Run at 75 to 80%

Hey Tom, thanks for the reply. I don't think cleaning it is the solution here though -- we can currently get the blue line to give 1W of output whereas its max is 1.5W, so it may not be perfect but is still decent enough. We also had the green line we're looking for, just a few days ago, so we know it at least can work.

[catalanjo]

@ "we would only need to adjust the vertical knob? "

probably YES! ( @ high current and with aperture full open and correct goggles)

(may need a tiny tweak on horizontal ... always back and forth to be able to return to original position)

Cheers

[optonano]

@ "we would only need to adjust the vertical knob? "

probably YES! ( @ high current and with aperture full open and correct goggles)

(may need a tiny tweak on horizontal ... always back and forth to be able to return to original position)

Cheers

Hi Catalanjo, thanks for the reply.

Rocking the vertical (pressing down on the knob) should be equivalent to (quickly) adjusting through all values of the vertical, right?

[catalanjo]

Yep, but slightly more chance of dis-adjusting the horizontal than just turning the knob and the "flash" might be very, very quick.

Best stick a bit of tape on knob to mark vertical start position then just turn knob slowly till green appears !

If after complete turn no green, go back find blue again (tweak horizontal for max power out) then turn in other direction.

Repeat process with a bit more "turn" until green appears..... if not as last resort.......

Or .... just wait for Steve to get back online.

Cheers

[optonano]

Yep, but slightly more chance of dis-adjusting the horizontal than just turning the knob and the "flash" might be very, very quick.

Best stick a bit of tape on knob to mark vertical start position then just turn knob slowly till green appears !

If after complete turn no green, go back find blue again (tweak horizontal for max power out) then turn in other direction.

Repeat process with a bit more "turn" until green appears..... if not as last resort.......

Or .... just wait for Steve to get back online.

Cheers

Hi Catalanjo,

So I just went and tried it again. I turned the machine up to the max current it'll deliver (~40A), tuned to the blue line, with the iris wide open. From there I tried rocking the vertical, but didn't see any other lines.

So, I tried adjusting the horizontal a little (still on the blue line), such that that it was visibly lowering the intensity of the beam (looking at it scatter off a rough piece of tissue ~3m away), but still on the blue line (just not at its max). From there I tried rocking it, and lo and behold noticed another line!

However, I'm pretty sure this line isn't the very "green" green we had before (probably 514nm), but it was in between, kind of an aqua (so maybe the 496 or 501 line?).

Annoyingly, at this point the interlock shut it down because we've been having trouble with our water flow in the building so it wasn't cooling it sufficiently.

I'll be back soon.

[catalanjo]

Strange that green you describe is usually more difficult to find than the bright lemon green you are looking for

Two things that Steve said a while ago are bothering me a bit !

"Depending on factory option, the rear optics mounts are designed to have their own internal adjustments for tracking."
"It is wise to wait and see what is really wrong before advocating traditional style operator work on this unit. It's not a 164."

I have not had the pleasure of meeting your model Spectra, and the manual sheds very little light on it's design.

However you seem to have got the hang of how to look for different lines and you now know which way to turn towards green.

In theory, the green you want is about double the angle (away from blue) than the one you have found !

So maybe it's just a question of keep rocking till you get there!

Just don't do anything rash and wait for further advice from Steve who seems to know your model ..... or maybe

Cheers

PS what tube voltage have you got when running flat out? (you find this out from the control panel = blue scale in the middle).
Low pressure/voltage can sometimes inhibit green line!

[mixedgas]

Steve was dragged into a violent incident last night and did not get to bed till 2Am. I'm OK, not at fault, and exhausted.

Severe rocking and scanning of the rear plate calls for removal of the Brewster stem cover so you do not crack off the window that contains the plasma and the pure gas. It slips off. Its job is to keep dust off the window.

If you got the cyan-green lines, you certainly can get 514.5, it has more then twice the gain of those lines.

I need to go sleep. Get your cooling fixed.

Steve

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Steve was dragged into a violent incident last night and did not get to bed till 2Am. I'm OK, not at fault, and exhausted.

Severe rocking and scanning of the rear plate calls for removal of the Brewster stem cover so you do not crack off the window that contains the plasma and the pure gas. It slips off. Its job is to keep dust off the window.

If you got the cyan-green lines, you certainly can get 514.5, it has more then twice the gain of those lines.

I need to go sleep. Get your cooling fixed.

Steve

[catalanjo]

Severe rocking and scanning of the rear plate calls for removal of the Brewster stem cover so you do not crack off the window that contains the plasma and the pure gas. Steve

That translated means ... DEATH OF TUBE...

Bummer is that to loosen the brewster covers you have to take the lid off the head. (with the laser UNPLUGGED from mains).

So gently does it .... when doing vertical scan.

Maybe the was a bit exagerated ! ... as was ..

Cheers