Which Power Value Should Be Used for Calculating Power Density in Pulse Lasers?

[breezels]

For pulse lasers, thers are two parameters describing its output power.
One is "the average power",which equals to the product of the energy of single pulse and the pulse repetition rate(per.second.);
the other is "the peak power", which is defined as the ratio of the energy of single puse to pulse duration.
My question: When we want to get the values of "power density(w/cm2)",
which power value( "the average power" value or "the peak power" value )should be used as the output power in the calculation?

 

[Integral]

I would think that the average power would be the more meaningful in this case. But there is a direct relationship, the area of the pulse is directly proportional to the average power so if you are careful it should not matter.

This is a quick off the top of my head response. I will see if I can learn any different when I get to my references at work.

 

[Gokul43201]

My question: When we want to get the values of "power density(w/cm2)",
which power value( "the average power" value or "the peak power" value )should be used as the output power in the calculation?

It depends on what you're using the power density (or intensity) for.

 

[breezels]

It depends on what you're using the power density (or intensity) for.

For example: nanosecond pump pulse lasers are used in my experiments--stimulated Raman scattering Experiment.
As long as the pump intensity (W/cm^2) exceeds some threshold value( at least 1.0 MW/cm^2) , the stimulated Raman scattering would occur.
For this case, the peak power is chosen. Right?

 

[ZapperZ]

If all you care about is the output power of your laser, you could easily verify it by using a power meter. There are power meters that work under both pulse and cw operations.

Zz.

 

[Gokul43201]

For this case, the peak power is chosen. Right?

Yes, that sounds right.

 

[armandowww]

For example: nanosecond pump pulse lasers are used in my experiments--stimulated Raman scattering Experiment.
As long as the pump intensity (W/cm^2) exceeds some threshold value( at least 1.0 MW/cm^2) , the stimulated Raman scattering would occur.
For this case, the peak power is chosen. Right?

If you use a laser emitting an average power so loud, you'll surely find output mirror melted, after broken.

 

[breezels]

If you use a laser emitting an average power so loud, you'll surely find output mirror melted, after broken.

Yeah! This situation may occur.But sometimes a fused-silicon glass
could withstand the intense power.

 

[Mindscrape]

Class IV lasers

I have a question, are class IV lasers actually bad for your skin? I work with some class IV lasers, and if I want to temporarily block a beam I will usually just put my hand in the way. I suppose that exposing yourself to any sort of radiation is generally not good for you, but I don't suppose that it's really harmful at all.

 

[breezels]

I have a question, are class IV lasers actually bad for your skin? I work with some class IV lasers, and if I want to temporarily block a beam I will usually just put my hand in the way. I suppose that exposing yourself to any sort of radiation is generally not good for you, but I don't suppose that it's really harmful at all.

Do you have an black iron plate ?It can block the beam instead of your hands.

 

[Gokul43201]

From the OSHA Technical Manual, SECTION III, CHAPTER 6 : LASER HAZARDS

f. Class IV: High power lasers (cw: 500 mW, pulsed: 10 J/cm2 or the diffuse reflection limit) are hazardous to view under any condition (directly or diffusely scattered) and are a potential fire hazard and a skin hazard. Significant controls are required of Class IV laser facilities.

http://www.osha.gov/dts/osta/otm/otm_iii/otm_iii_6.html

 

[Mindscrape]

Oh, I didn't realize that Class IV were 500mW, it must just be that we have the Class IV laser hazard on our door for some kind of safety reason (maybe we have one laying around), though all the ones we have must be Class III since they are around 100-200mW (which is still nothing to scoff at). Yeah, we do have iron plates around, but I'm using that to block off my split beams. Just sticking your hand in and out real quick to see how well a laser is coupled can't really be bad for you.