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Constant power

teddybearninjaz

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I'm trying to do a lab experiment with a laser but I need the light to be constant or it'll affect my data. I'm currently using a green laser (<5 mW, 532 nm) that uses two AAA batteries. Is there a way that I can connect the laser to a constant power supply? Or perhaps could someone direct me to a better laser? It would help if I didn't have to hold the button down and could just use a switch. I know almost nothing about lasers so please help! Thanks!
 



BShanahan14rulz

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You'll need to buy a laser with stabilized power via optical feedback. Depending on how stable you need it, you're looking at ~$50 for a cheaper one to thousands for a lab-grade, astronomical, wavelength locked, optically stabilized, super-deluxe GTX-r laser.
 

Cyparagon

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We can help you a lot better if you actually tell us something about your experiment, you know ;)
 

ARG

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Even if you apply constant power the output of the laser will vary with temperature changes and humidity.
 

Bionic-Badger

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Some of those green lasers often have optical feedback control built-in (those wires that come from the front).

I wouldn't use a DPSS green though. All those different variables involving the laser strength, the temperature of the crystals, etc. can make it harder to control. Use a diode laser and regulate it using feedback from an optical sensor or something like that.
 

teddybearninjaz

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I'll explain a little bit more. Basically I'm measuring the concentration of a chemical in a polymer by judging how much it luminesces when shining a laser light onto it. It's not too fancy but I would like some consistency.

I'm currently using this laser pointer: Amazon.com : Green Remote Control Laser Pointer Laser Presenter for Teaching or Office : Electronics

Sometimes it's very bright but it usually dims after a while... even on fresh batteries.

I've been looking at possibly using this: Amazon.com : INFINITER 2000 Ultra Bright Green Laser Pointer/ Emits ultra bright green laser beam over 1000 yards : Electronics

or this: Amazon.com : Quarton Laser Module VLM-532-42 LPA (ECONOMICAL GREEN DOT LASER) : Laser Pointers : Electronics

Any thoughts?
 

ARG

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Does it have to be 532nm? DPSS lasers are notorious for being unstable.
 

teddybearninjaz

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Yes. What is DPSS? Would the lasers I picked out above dim out quickly? I just need it to be fairly consistent. Sorry that I don't know much about this.
 

styropyro

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Basically a DPSS 532nm laser takes IR light and uses special crystals to convert it into 532nm light. These are typically unstable, especially for cheap pointers. If you want a very stable 532nm laser, you are likely looking to pay a bit more.

I'd suggest buying a 520nm 5mW laser module and using that. These modules are diode based so don't fluctuate in power much. Optimally you would run it on a TEC temperature regulator, but I bet you could get away with running it for ~10min to let the module's temperature equilibriate and then use it there.

And yes I saw that you need 532nm specifically, but 520nm is close enough in wavelength that it should act similarly to 532nm in your experiment. You will just need to make a standard plot of the fluorescence of the chemical you are detecting at known varying concentrations and use the fit curve to analyze the fluorescence of your unknown in the experiment.
 




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