How to determine the Intensity or power of laser beam...?

EU? europe? no man im from asia... :/ the specs here said greater than 1mW i dont know if I should believe but it does shine very bright tho. i computed the divergence it ranges from 1.08-1.33 mrad. so im guessing 1.25+mW?

Elektr0n3Ro9000 said:

EU? europe? no man im from asia... :/ the specs here said greater than 1mW i dont know if I should believe but it does shine very bright tho. i computed the divergence it ranges from 1.08-1.33 mrad. so im guessing 1.25+mW?

Click to expand...

For the power you want to test you can get one of these...

Products

or you can try to build one yourself. Look at the links
at the bottom of this Thread Post.....

http://laserpointerforums.com/f70/l...based-laser-power-meter-40116.html#post520850

But remember... you will still need to calibrate your DIY
LPM to another known calibrated LPM for it to be accurate.


Jerry

You can contact us at any time on our Website: J.BAUER Electronics

one more super last question (im so sorry really.) for your sides since you have those equipments do you think that the larger the divergence/ or the spot size, the greater the power? as I can observe the larger the power the smaller the beam size... as I've seen with other expensive high powered laser. do you agree? thanks!

no. the divergence, or how much the beam gets wider over distance, is not connected with output power. I mentioned this in post #4.

A laser outputs what it outputs. The beam can be wide or small. The two are not related.

If your Laser outputs 100mW and the beam is 1cm X 1cm (1cm2) then
the Power Density of the Laser on that surface is 100mW/1cm2.

If the same 100mW Laser projects a beam 10cm X 10cm (100cm2) then
the Power Density of the Laser on the same area is only 1mW/cm2.

It is the same amount of power but spread over a larger area. The power
does NOT increase but the Power Density goes down...


Jerry

You can contact us at any time through our Website: J.BAUER Electronics

Elektr0n3Ro9000 said:

one more super last question (im so sorry really.) for your sides since you have those equipments do you think that the larger the divergence/ or the spot size, the greater the power? as I can observe the larger the power the smaller the beam size... as I've seen with other expensive high powered laser. do you agree? thanks!

Click to expand...

Don't be afraid to ask more questions. That doesn't need to be your last question.

Jerry (Lasersbee) covered the power density part. One thing about a smaller beam is that it has a greater divergence. At a larger distance, when a laser is focused at infinity, the spot size of a laser with a small beam at the aperture (the opening) will be larger than the spot size of a laser beam that is larger at the aperture.

So if you want to retain an overall smaller beam at a great distance you should have a larger beam size when you start out.

Bionic-Badger said:

So if you want to retain an overall smaller beam at a great distance you should have a larger beam size when you start out.

Click to expand...

I think I have to disagree with Bionic. Sorry. Beam divergence (without corrective optics) is what it is from a laser. It may be really great, or it may be really bad raw coming out of the source.

A Helium Neon gas laser can have awesome (tiny) divergence. Many laser diodes have really poor divergence. Those laser diodes with poor divergence, once you start trying to make them better, using optics, it becomes the trade-off Bionic described. You may need to make those beams wider, in order to have a dot at some far away distance.

But this issue does not apply to all lasers.

All Laser Diodes without optical corection have very large
divergence... it is the nature of the beast.

Raw LD beam divergence can't be compared to a raw He-Ne
beam... They are 2 different technologies.

What BB stated is at the output aperture of an already collimated
LD and is known to be correct. That is why Beam Expanders
were invented...


Jerry

You can contact us at any time on our Website: J.BAUER Electronics

Elektr0n3ro9000

What lasersbee said is absolutely correct. HeNe gas lasers will have better beam specs than diode lasers without corrective optics. Single mode diode lasers tend to have better divergence than multi-mode diode lasers. Fast axis correction (FAC) can improve the beam shape of multi-mode diode lasers prior to using other optics for controlling divergence and/or focus.

For example, I use a 50W FAP 808nm 19 emitter bar diode laser, running at about 25 watts. Due to divergence, without a FAC optic in front of each of those diode emitters very little of the 808nm would actually enter each of the 19 fibers. Those 19 fibers are bundled to produce a quasi-round output from the FAP module. I then use an adapter with an aspheric lens to focus that output into a large Nd:YAG crystal, which lases at 1064nm. That output is then fed into a large KTP crystal that doubles the frequency (halves the wavelength) to 532nm at about 7 watts. This is then directed into a 5" telescope in reverse, which functions as a beam expander. If I focus this onto a retroreflector on the moon, I can observe the reflection quite well. If I omit the 5" telescope beam expander, I cannot focus the beam tightly enough to get a visible reflection from the moon. Without the beam expander, the divergence is too high, no matter how well I try to focus the beam. Beam density is just too low by the time it makes it to the moon.

Bob