NOTE: in part 2 the energy density is the energy per cubic meter. A laser pulse

Question

NOTE: in part 2 the energy density is the
energy per cubic meter.
A laser pulse has an energy of 28 J and a
beam radius of 3 mm. The pulse duration
is 11 ns and the energy density is constant
within the pulse.

What is the spatial length of the pulse?
Answer in units of m.

part 2 of 4
What is the energy density within the pulse?
Answer in units of kJ/m3.

part 3 of 4
Find the electric amplitude of the laser pulse.
Answer in units of MV/m.

part 4 of 4
Find the magnetic amplitude of the laser
pulse.
Answer in units of T.

Explanation / Answer

(1)

the spatial length of the pulse is

L = c del t = 3 * 10^8 * 11* 10^-9 s = 3.3 m

(2)

the energy density within the pulse is

u = U/V = U/ pi r^2 L

= 28/ pi ( 3.0* 10^-3)^2 3.3

=300.24 kJ/m^3

(3)

E0 = ( 2u/ eo)^1/2

= ( 2 (300242.338)/ 8.85 * 10^-12)^1/2

=260.48 MV/m

(4)

Bo = Eo/c = 260482966.66/3.0* 10^8 = 0.868 T

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