JDS Argon is not doing 60mW. Tweaking questions.

NateTheGrate · Jun 18, 2013

I have a JDSU Mod 2011 65ML argon laser I cadged from an NIH warehouse, but when run on light feedback mode, I can only get about 15-25mW multiline from the argon (varies which meter (Si/bolo) is reading it). It is in an older Leica confocal microscope I have pretty well resuscitated. The unit may have overheated (limit) on idle a couple times. The tube only has about 1500hours, but wondering if there is any thing I should do. I am a very poor lab rat researcher with sequestration. Its on a big fan, runs stable, just never increasing past 15mW at 7V on the 0.1V/mW regulation of pin 7. Starts fine, runs stable if not over 9V on pin 7.
Inside I has this style head, with a funny ring on the front end...

Questions:
1. Tweaking the JDSU laser unit head, like adjusting the mirrors/brewster prisms/screws. Anyway to do this safely? My beam seems to be coming out very angled, and low power. Will this increase optical power. The rear of the unit seems to just be a mirror.

2. I was advised to check the filament voltage..how to do this on a JDSU supply, I only see current and light output regulation?

3. Try another supply, I was advised sometimes the JDSU supplies die. Where to get another that will drive 65mW or more, on the cheap?. I guess it has to be fairly stable for confocal work...:thinking:

4. Turning the optical power pot, the light output increases rapidly..and then never goes farther..up to 7V on pin7. Does this tell you my problem?

pschlosser · Jun 18, 2013

1. I am surprised you can even see the amount of skew coming from the laser. I tried to find the specs on the bore diameter, because what you are describing seems unlikely, given the bore diameter is smallish. Presuming your diagram accurately depicts what is going on inside the laser, my hunch is there just isn't enough room in the bore for a beam to lase askew and emit at an angle large enough for you or me to detect.

With that said, if it is doing (internally) what you describe, the only way I know how to correct the HR mirror is a full alignment, which means pulling the OC mirror off, and using a procedure similar to that discussed on Sam's website repairfaq.org. In that procedure, one shines a HeNe into the open end of the laser from across the room, and one attempts to adjust the HR until it shines right back into the HeNe.

Is it possible that the feedback optics, the one's that tell the PSU what power the laser is emitting, is it possible that assembly is skewing the output beam?

2. Again, refer to Sam's website for schematics. If memory serves, the filament voltage is the voltage that approached 500VDC, so make sure you have appropriate test equipment. I'm not sure what the voltage will tell you, if she lases and responds to light output changes at the pot.

3. The JDSU 2210 PSUs are pretty common place. I've purchased a few from eBay. I own several. Again, if your tube fires up immediately, has the low hours you're suggesting, it may not be the supply. But either buying one or finding someone with one of these heads so you can borrow one is your best bet. If you're going to pay to have one shipped to you (on loan) you may as well buy another. For the cost of return shipping may cover the bulk of the cost for a second PSU.

4. Does not 7.0V indicate 70mW ? Do you have an LPM to test the output and see a second opinion? If she is outputting 70mW, that may be the limit.

The size of the tube pictured looks very similar to the JDSU 2214 family of air-cooled Argon Ion lasers. As such, these (ML) are rated for (at most) 35-40mW. While I own some tubes from this family that emit powers in the 80mW and 120+mW, they only do so fully cranked up. And at full power, the tube life is rated for only a few hundred hours. Back the power back down in the 6A range, and they emit around 40mW, just what they are rated for, with 1000s of hours of run time expected. These numbers refer to ML models. SL (single line) models will output much lower, depending on the wavelength.

Cyparagon · Jun 18, 2013

pschlosser said:
2. Again, refer to Sam's website for schematics. If memory serves, the filament voltage is the voltage that approached 500VDC

Not even close

The filament voltage is simply the voltage across the filament. Set your meter to AC volts, and measure across the two terminals coming out of the back. It should be somewhere around 2.7V.

This terminal, and the one next to it (out of view):

pschlosser said:
Does not 7.0V indicate 70mW ?

No, pin 7 is light adjust. Pin 8 (or sometimes pin 9, evidently) is the power reading.

Op: measure the voltage on pin 8, multiply it by 10, and that should give you an accurate power reading. Also report on what pin 9 reads, if you please.

NateTheGrate · Jun 18, 2013

Power Measurements: Fluke DMM.

OK, Here is what I get using Pin 11 Return (Gnd Circuit). Mega air cooling.

Idle: Pin 8 0.87VDC Pin 9 0.40VDC Pin 7 command volt:0V
Full: Pin 8 4.53VDC Pin 9 0.68VDC Pin 7 command volt 4.74VDC (~47mW).

It seems to be peaking in power output early on the light drive of pin7 if this helps. :undecided: And the beam exits very angled down, as I had to redrill KineFLEX to get the fiber align controls anywhere near the beam.

I have not measured the filament voltage yet. Open case to do after lasing, with good insulation?

pschlosser · Jun 18, 2013

Thanks Cyp, for the clarification.

Cyparagon · Jun 18, 2013

According to those readings, what you call "full" is only 6.8A of tube current. As I understand it, something around 8A is the best trade-off between power and tube life, but they can handle up to 10A or so. You can try increasing the voltage to pin 7 a bit and see if that changes anything, or you can switch to current-mode operation.

I don't think you need to measure filament voltage; everything looks in order except for the exit angle. I'm not sure what to make of that. Picture?

If you want to measure it anyway, turn the laser off (shutdown mode or whatever), but leave everything plugged in. The filament will usually remain ON even when the laser is off. It will create minimal heat in this mode, so it is safe to remove the cover and cooling.

NateTheGrate · Jun 19, 2013

I am trying to cook it at mid power for a day at 13mW to see if it outgasses, or should I say degasses? Add more power does nada right at the moment.

At first when I got this unit, I used the Leica front panel argon laser power control which can take pin 7 on the JDSU power supply DB25 up to 15V. When the laser got around 10V or more it started to make a "chattering" noise, and I immediately cut the power. After all 10V is commanding the unit to go 100mW, when my 65ML tube is only rated 65mW.

So I installed a limiter pot in series with the control pot to not allow the power control voltage to get into the chatter region, where I am not sure what is happening but when it chatters, it sounds like it could damage the tube. Lasing is unstable? :undecided: Argons are reported to run longer when at lower power anyway, (although above idle).

OK, the overnight cooking verdict (with cooling). NADA.

In the AM the beam was still at 13mW, it did not change a bit from 13mW.

The AC filament voltage on the unit reads 2.8VAC at start (non lasing) and when heated runs about 2.78VAC (non-lasing).

So what to do to bring this baby anywhere near JDSU Mod 2011 65ML rated 65mW? I could live with 30mW, really.

http://laserpointerforums.com/images/smilies/thinking.gif

The back mirror (near the filament looks a little saggy), not sure if these guys move, or can you move them safely. The unit has 1500 hours but maybe was run hard? Or maybe the filament sagged from overheat a couple times on idle.

Fooled by silicon detector power meter saturation...
Well, I was about to give up, and started mounting the optical fiber on it.

Aligned the fiber...and the output of the fiber was again 13mW! Now.... How did I not lose any power through the optical fiber...I got to thinking .

...It was this guys Silicon Detector on a 1930C Newport Power Meter I borrowed. Apparently at 488nm it saturated at 13mW, but it did not tell you. Sliding the 3.0 OD ND filter in the head made it read 35mW output out of the fiber, and probably more straight from the laser (but I wish to avoid realigning polarized optical fiber). Now that is more like it, and I can probably work with this on my confocal microscope if I carefully align things.

So I learn, don't trust Si detectors for power readings. They are fast and sensitive though, but they saturate in wierd ways. Back to bolometers I guess.

So thanks everybody for your help. I usually work with irradiance and lux, so power measurements are a little foreign to me with lasers.

Sigurthr · Jun 20, 2013

How about running the laser in Current mode and setting the current to 7 to 9.5A (the normal safe operation range)?

pschlosser · Jun 20, 2013

Sigurthr said:
How about running the laser in Current mode and setting the current to 7 to 9.5A (the normal safe operation range)?

9.5A seems a bit high, to me. But the 6-7A range is a great compromise between tube life and output. Consider the following chart (courtesy Sam's Repair FAQ site) for the ALC 60X Air-cooled Argon Ion Laser, much like these JDSU units.

Code:

 Tube	------- Output Power --------
Current	All nm 	457nm	488nm	514nm	Lifetime (Hours)
4A	10mW	1mW	7mW	0mW	15,000-25,000 Hours
6A	30mW	2mW	17.6mW	7.5mW	8,000-15,000 Hours
8A	70mW	5mW	27mW	23mW	4,000-6,000 Hours
10A	130mW	10mW	44mW	42mW	1,500-2,000 Hours
12A	200mW	15mW	60mW	68mW	1,000-1,500 Hours
14A	280mW	22mW	81mW	98mW	500-1,000 Hours

Observe that at 4A, tube life could be as low as 15,000 hours. But at 10A, only 1,500, and at 14A, 500 hours. The curve really begins to ramp up over 8A.

NateTheGrate · Jun 30, 2013

I think the JDS laser DB25 connector is set by Leica to regulate light output to the beam scan head on the microscope. For microscopy, this ensures the beam intensity at the specimen stays uniformly bright. I put in a variable limit resistor in series with their argon laser 10K power intensity pot on the front cabinet panel, to allow about 70mW max. So far so good and no chatter.

Now the beam is out of the AOTF, and into another polarized fiber to the microscope scan head. It seems to need aligning in the scan head. Lots of red marked screws here.

diachi · Jun 30, 2013

pschlosser said:
With that said, if it is doing (internally) what you describe, the only way I know how to correct the HR mirror is a full alignment, which means pulling the OC mirror off, and using a procedure similar to that discussed on Sam's website repairfaq.org. In that procedure, one shines a HeNe into the open end of the laser from across the room, and one attempts to adjust the HR until it shines right back into the HeNe.

Is it possible that the feedback optics, the one's that tell the PSU what power the laser is emitting, is it possible that assembly is skewing the output beam?

2. Again, refer to Sam's website for schematics. If memory serves, the filament voltage is the voltage that approached 500VDC, so make sure you have appropriate test equipment. I'm not sure what the voltage will tell you, if she lases and responds to light output changes at the pot.

The optics on these tubes cannot be removed ( Well they can ... but the tube would go up to air... ) - they are hard sealed - you can attempt to adjust them by "bending" them while the tube is running using an insulated rod ( I've used BIC pens with the ink tube removed ) - The OC mirror on these is connected directly to the anode, so it's sitting at up to 100-115VDC when the tube is running.

Filament voltage on these is usually 2.6-2.8VAC.

pschlosser said:
9.5A seems a bit high, to me. But the 6-7A range is a great compromise between tube life and output. Consider the following chart (courtesy Sam's Repair FAQ site) for the ALC 60X Air-cooled Argon Ion Laser, much like these JDSU units.

Code:

Tube ------- Output Power -------- Current All nm 457nm 488nm 514nm Lifetime (Hours) 4A 10mW 1mW 7mW 0mW 15,000-25,000 Hours 6A 30mW 2mW 17.6mW 7.5mW 8,000-15,000 Hours 8A 70mW 5mW 27mW 23mW 4,000-6,000 Hours 10A 130mW 10mW 44mW 42mW 1,500-2,000 Hours 12A 200mW 15mW 60mW 68mW 1,000-1,500 Hours 14A 280mW 22mW 81mW 98mW 500-1,000 Hours

Observe that at 4A, tube life could be as low as 15,000 hours. But at 10A, only 1,500, and at 14A, 500 hours. The curve really begins to ramp up over 8A.

8A is the widely accepted maximum safe current for these JDSU units.You can run at more than that, but tube life decreases somewhat significantly. 8A is a good trade-off.

Also the ALC-60 while air-cooled and similar in size is not as "rugged" as the JDSU tubes. The filament isn't as tough, the mirrors aren't sealed, etc.

NateTheGrate said:
I think the JDS laser DB25 connector is set by Leica to regulate light output to the beam scan head on the microscope. For microscopy, this ensures the beam intensity at the specimen stays uniformly bright. I put in a variable limit resistor in series with their argon laser 10K power intensity pot on the front cabinet panel, to allow about 70mW max. So far so good and no chatter.

Now the beam is out of the AOTF, and into another polarized fiber to the microscope scan head. It seems to need aligning in the scan head. Lots of red marked screws here.

Is the beam coming out at an angle from the AOTF or is it like that directly from the aperture of the head?

If it's coming out like that directly from the aperture it could either be that the feedback optics ( as suggested before ) are skewing the beam or the tube isn't sitting straight in the head.

If it's coming out at an angle from the AOTF then that's normal.

NateTheGrate · Jul 1, 2013

My JDS end has a black mount that has an output hole that sort of looks like a keyhole. The multiline argon beam is coming out at a slight down angle (<5 deg), and I finally found a KineFlex position of the coupler where the alignment screws could couple to it. So since my watt emission issue was a meter saturation issue underreporting the performance, I am not going to mess with the JDS tube mirror ends.

My laser end looks like the previous picture, and I cannot put an empty BIC pen around it as it is about 12mm in diameter at the mirror. (I did try pushing the mirror slightly with a Delrin rod, but it is very rigid).

For AOTFs, what you said about the 2 beams is correct. The straight one is modulated by the unit, and the other comes out at a diving angle. I have coupled the correct modulated beam to the fiber optic here.

The fiber optic output of the AOTF is heading into this complex head on my confocal scanner module, where I have shown the coupler in the photo. Wish me luck with the screws (avoiding the red ones).

--I have the single visible laser input, 2 PMT version of this head.

JDS Argon is not doing 60mW. Tweaking questions.

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