New to lasers, questions about power

[photochemist]

Hi all! I am pretty new to lasers. I am a graduate student in chemistry and I’ve been trying to use lasers to do some chemical reactions. I have had success with a 405 nm laser pointer which I borrowed. It was sold as 5 mW but also labeled max 100 mW, which confused me. I’d like to buy my own, but I’m wondering what power to go for to get something similar. The company stopped selling that particular laser.

Also, how accurate are those power ratings? I’m wondering if I should be measuring the laser’s output myself so that I have that information when I publish my results. Does the output of a laser pointer vary from day to day, or as the batteries get low?

I have ventured pretty far outside of my own and my advisor's realm of expertise with this project so it's a bit like the blind leading the blind. Thanks for any help you can provide.

 

[SpinozaQ]

Diode lasers are going to have a range of power that they will operate at. Below the minium range they may "Go LED", which means, they emit light, but will not lase. The maxium power is due to COD, "Catastrophic Optical Damage", or heat disapation, or both.

If you are doing research you should measure the power output with a meter. I'm not a research guy but I imagine that is a really important data point to have.

The laser's power can vary based on the driver circuit choosen, and yes, a battery driven laser could absolutely vary ouput power as the batteries drain.

 

[pschlosser]

Also, how accurate are those power ratings?

International sellers are not subject to the false advertising consequences that most domestic (to the US) sellers are. As you may know, the bigger and more powerful a laser is, the more you can charge for it. As such, you may find that many claims are just, well, untrue and over-stated.

Many posts on this website attempt to deal with this disparity. Look in the “Companies” forum for those companies to avoid, and those to seek out. The "Buy Sell Trade" section is a good place to buy from someone with a positive reputation.

Regarding labeling. A 5mW laser is, in fact, less than 100mW. To save costs, A company might print up labels indicating the product is <100mW, and then stick them on 5mW, 25mW and 75mW lasers. After all, they are in fact less than 100mW. The FDA is paying more and more attention to laser product sales. To avoid confiscation of a laser product, a seller may sell you an actual 1000mW laser, but claim it is only 5mW on the paperwork, or the warning label, in order to navigate through customs.

The bottom line is, we can neither trust the claim OR the label, when buying products from outside the US. But this problem isn't limited to international sales. Even some domestic companies are known to bend the truth a little... or a great deal.

Experience, trial and error, show us who is truthful, and who is unscrupulous. Light Power Meters (LPM) are the best way to tell if we got what we ordered. If you have a collection of laser pointers of known strengths at the same wavelength, one can compare relative brightness with the unknown laser pointer, and get an idea for where its output power lay.

 

[lasersbee]

Hi all! I am pretty new to lasers. I am a graduate student in chemistry and I’ve been trying to use lasers to do some chemical reactions. I have had success with a 405 nm laser pointer which I borrowed. It was sold as 5 mW but also labeled max 100 mW, which confused me. I’d like to buy my own, but I’m wondering what power to go for to get something similar. The company stopped selling that particular laser.

Also, how accurate are those power ratings? I’m wondering if I should be measuring the laser’s output myself so that I have that information when I publish my results. Does the output of a laser pointer vary from day to day, or as the batteries get low?

I have ventured pretty far outside of my own and my advisor's realm of expertise with this project so it's a bit like the blind leading the blind. Thanks for any help you can provide.

As was stated above... the labeling on a common laser will
be shown as <XXXmW. That is because not all Lasers will
output the exact same power for the same Batteries and
electronics. The identical common Laser will vary in output
power. The cheaper Chinese Laser are even worse as to
labeling.

Lasers will also change their output characteristics with
battery voltage changes and changes in ambient temperatures
as well as internal Laser heating.

Since you are attempting to do some scientific experimentation
and document it I would suggest either getting a known power
tested Laser with certificate or better still purchase a Laser Power
Meter (LPM) and test your Laser at the time of the experiment.

This would assure a more precise experiment documentation.


Jerry

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