question 1)

If something is exposured to the laser during 10 sec, how much energy does it absorb ? ignore the absorptance and emissivity.

question 2)

What does it-20W- mean ? Does it mean summation of energy of unit area in laser beam ?

- Thread starter jjangdori
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question 1)

If something is exposured to the laser during 10 sec, how much energy does it absorb ? ignore the absorptance and emissivity.

question 2)

What does it-20W- mean ? Does it mean summation of energy of unit area in laser beam ?

L

In order to answer your question you need to know the pulse length and the spot size on the target. I can just make a guess that it is around 10 nanoseconds and 1 mm and run the numbers.

100 uJ/10 ns = 10000 watts

so if you have a beam diameter of 1 mm the area of the spot is

(0.05 cm)^2*pi = 0.0078 cm^2

so the intensity would be 10000 watts/.0078 cm^2 ~ 1.3 MW/cm^2 about 1.3 megawatts per square centimeter.

If you expose something for 10 seconds and it is a 20 watt or 20 joule/second laser it would absorb 20 J/s * 10 s = 200 Joules.

Hope that helps

I know that the spot size is 50 micrometers. but I coun't find the pulse length... is it duration? if it is...

How can I obtain the value of duration... the frequency of laser is 1064 nm....

L

If the spot size is 50 microns assuming a pulse length of 10 ns gives the intensity of about 0.5 GW/cm^2. That is quite high and whatever you are hitting with it is most likely being ablated rather absorbing the energy into the bulk material.

Ok. my laser gives the intensity of about 0.5 GW/cm^2..

so, anywhere in laser spot, is it equl? I know that TEM00 laser has gaussian distribution...

absolutely... The intensity at center of beam spot is higher than 0.5GW/cm^2 ?????

L