When a high-power laser is used in the Earth\'s atmosphere, the electric field a

Question

When a high-power laser is used in the Earth's atmosphere, the electric field associated with the laser beam can ionize the air, turning it into a conducting plasma that reflects the laser light. In dry air at 0Ý°C and 1 atm, electric breakdown occurs for fields with amplitudes above about 3.00 MV/m.

power laser is used in the Earth's atmosphere, the electric field associated with the laser beam can ionize the air, turning it into a conducting plasma that reflects the laser light. In dry air at and 1 atm, electric breakdown occurs for fields with amplitudes above about 3.00 MV/m. What laser beam intensity will produce such a field? At this maximum intensity, what power can be delivered in a cylindrical beam of diameter 6.57 mm?

Explanation / Answer

a) |S| = (1/u) |E x B|
= (1/u) EBsin? = uEB

E/B = c
E = cB

|S| = (1/u)cE^2

S_average = (1/u)c[(E_max)^2*sin^2(wt)]_average
= 1/(2u)c*(E_max)^2

I = S_average

b) I = P/A
P = IA = I*(pi)*(d/2)^2

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