Laser Energy distribution

[petpig]

Hello,
Anyone has an idea how power (energy) is distributed when a .81mm diameter HeNe laser shines on a circular area of 0.4mm ? Are all the points on the shined suraface having the same amount of energy ?
First post in this forums.
Thanks all!

 

[ElektroFreak]

Hello,
Anyone has an idea how power (energy) is distributed when a .81mm diameter HeNe laser shines on a circular area of 0.4mm ? Are all the points on the shined suraface having the same amount of energy ?
First post in this forums.
Thanks all!

No. You'll want to research "gaussian power distribution" as understanding this will help you understand how power is distributed in a laser beam. Here's a link to a wikipedia article that should help: http://en.wikipedia.org/wiki/Transverse_mode

In a TEM00 beam (like most HeNe lasers produce) the majority of the power is concentrated in the center of the spot, and gradually becomes less intense as you move away from center along any radius. The best way to see what I'm describing is to use some dark sunglasses and look at the spot while projected on a wall at least 15 feet (~4.5m) away. You'll be able to see the power distribution a bit more clearly.

 

[petpig]

Many thanks you for your quickie reply !
The wiki page is extremely useful, however, there a point which I do not really understand the w which is "the spot size of the mode corresponding to the Gaussian beam radius" ... I tracked it back to

h**p://en.wikipedia.org/wiki/Gaussian_beam#Beam_width_or_.22spot_size.22

but i dont know where w0 comes from, my HeNe laser is .81mm collumated so I dont expect any change in the spot size at all ? I must be wrong then.

 

[petpig]

I'm using the 1137P in this page,

h**p://w*w.photonicsolutions.co.uk/datasheets/jdsu/JUHeNeLaserHeads_1100Series.pdf

 

[FrothyChimp]

w[sub]0[/sub] is the beam waist radius. The waist size is a function of the hemispherical OC mirror (and HR if it is not flat) and the resonator length, and is located within the resonator. It is used to determine the active area of the resonator which is directly related to the number of transverse standing waves available to the beam. In the case of TEM00 the waist is probably quite narrow and there might even be an aperture (although not likely for a HeNe.)