LPM recommendation

I'm in the process of trying to align the mirrors on a Siemens HeNe (this one). It's my first time, and I've read a lot of Sam's Laser FAQ, but, well, it's still my first time.

Anyway, one bit of help I could really use is a recommendation for a good LPM for this purpose. The one I have now is much better suited for higher power lasers, and in situations where response time isn't critical. When I tweak a mirror a little bit on this laser, it can take a good 5 seconds before the LPM readout adjusts. I can actually see a visible difference in power output from about 1 mW to 6 mW, but the LPM takes a while to update. Additionally, when the power output is below roughly 6 mW, the LPM has a tendency to reset to 0.

I posted this in the gas laser section specifically because I figure you guys would know best about which LPM is most applicable to tuning a laser, where I assume response time and extreme accuracy are more important than they are with comparatively higher power diode lasers.

I'm not afraid to buy a decent LPM, but a brand new lab-quality LPM is probably out of my budget. Any suggestions?

Lasersbee LPM's and the Radiant Alpha are both good LPM's

IIRC, lasersbee sells a LPM which reads in 0.1mW increments.

LaZeRz said:

Lasersbee LPM's and the Radiant Alpha are both good LPM's

IIRC, lasersbee sells a LPM which reads in 0.1mW increments.

Click to expand...

From looking at laserbee's web site, none of their LPMs are good for <5 mW, except for one that goes to 3 mW, but even that's cutting it close for this application.

My Coherent LaserCheck goes down to uW but I dont think it would be a good choice
unless you dont mind stopping to take readings.. If you dont already have one,
you have to keep holding down the button which for alignment is pretty pointless.

If you can get another person to take readings while you work, it may be an option :thinking:


*EDIT

Lasersbee also has an optical sensor you hook to a DMM.. this may be a good solution
just not sure what it will read down to, saturation etc..

Alignment works the best on a fast lpm (no laserbee or alpha). An Ophir oem head may be fast enough, but a good photodiode based lpm would be better, maybe with a neutral density filter on the photodiode to attenuate the beam a bit. Unless you need to monitor the absolute power realtime you can hook up a photodiode to a transimpedance amplifier and you have your signal. Very easy to make and very cheap.

Bluefan said:

Alignment works the best on a fast lpm (no laserbee or alpha). An Ophir oem head may be fast enough, but a good photodiode based lpm would be better, maybe with a neutral density filter on the photodiode to attenuate the beam a bit. Unless you need to monitor the absolute power realtime you can hook up a photodiode to a transimpedance amplifier and you have your signal. Very easy to make and very cheap.

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I agree with the the statement that a fast LPM is required
but don't say no LaserBee....:cryyy:
(i'm sure you were referring to our Thermopile LPMs)

We have a LaserBee Optical Laser Power Meter Module know
as the 200mW HLPM II that would work for his application of
aligning the Mirrors of a <30mW He-Ne Tube. The HLPM II reads
in increments of 0.1mW and no ND Filter would be needed.

We have already responded to the OP's PM to us this morning.

lasersbee said:

...(i'm sure you were referring to our Thermopile LPMs)...

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This ^^

I though the photodiode based stuff had a different name, my bad. I ment the thermal lpm's.

Bluefan said:

Alignment works the best on a fast lpm (no laserbee or alpha). An Ophir oem head may be fast enough, but a good photodiode based lpm would be better, maybe with a neutral density filter on the photodiode to attenuate the beam a bit. Unless you need to monitor the absolute power realtime you can hook up a photodiode to a transimpedance amplifier and you have your signal. Very easy to make and very cheap.

Click to expand...

That statement may be skewed by the reviews of the budget 2.5W USB edition. Yes that one has a long wind up but my 3.2W Laserbee II is very responsive and can be used for Alignment no problems.:beer:

Just ordered the laserbee optical LPM. I'll let you guys know how it works, and I'm sure I'll have more questions about mirror adjustment

DTR said:

That statement may be skewed by the reviews of the budget 2.5W USB edition. Yes that one has a long wind up but my 3.2W Laserbee II is very responsive and can be used for Alignment no problems.:beer:

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Agreed.. Been using my LB-I for ages setting up my 532's and some 473's.
Though it wont measure under 5mW, but in my case its not needed. Readings
are fast and very well suited for DPSS work..

You probably could've just used a much simpler solution like a cadmium sulphide photocell (light dependent resistor) or a phototransistor connected to an analog meter for very fast response times without needing to shell out $60 for a photodiode and some components shrink wrapped together, but I suppose it's too late to point that out now =P

MarioMaster said:

without needing to shell out $60 for a photodiode and some components shrink wrapped together

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Parts, design, assembly and calibration dont come for free..

I'd pay 70$, but I dont think Jerry spent enough time mixing epoxy :crackup:

wannaburn said:

Parts, design, assembly and calibration dont come for free..

I'd pay 70$, but I dont think Jerry spent enough time mixing epoxy :crackup:

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Someone sure is in a trolling mood lately :crackup:

MarioMaster said:

You probably could've just used a much simpler solution like a cadmium sulphide photocell (light dependent resistor) or a phototransistor connected to an analog meter for very fast response times without needing to shell out $60 for a photodiode and some components shrink wrapped together, but I suppose it's too late to point that out now =P

Click to expand...

I agree that a small <1 mm2 Active area Photo Diode and small ampilfier
could have been used as a reference point of greater or less readings...

But the HLPM II is Calibrated to a Lab quality Newport Laser Power
Meter and can show actual differences in power readings in 0.1mW
increments and has a usable active area much greater than a
Photo Diode at 9 mm2.

OMG.... MM that is low... I would have expected better from you...:cryyy:


Jerry

You two always seem to think I'm being nasty or something - he doesn't need anything calibrated to peak a gas laser's alignment, $2 worth off components would do just fine.

You mustn't read such negative energy into my posts, I think we'd all get along a little better

MarioMaster said:

Someone sure is in a trolling mood lately :crackup:

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Forgive me for finding the humor in a 25% increase in cost for your LPM which
one of your reasons was exactly that.. mixing epoxy :crackup: priceless...

Cant help myself sometimes