Question

(1.0.10) In femtosecond laser spectroscopy, a laser pulse is created which is so short that the
entire pulse arrives at a fixed target in well under 1.0 ns. Suppose a 50.0 fs (f = 10-15) laser pulse
with a circular cross-section is created. The power delivered by the pulse to a target is 10.0 kW,
and the diameter of the beam is 20 µm.
(a) What is the length of the pulse?
(b) What is the intensity of the pulse?
(c) What are the maximum electric and magnetic field strengths in the pulse?
(d) The wavelength of the pulse is 850 nm. How many wavelengths are in a single pulse?
(The actual pulses have a range of wavelengths; we’re just keeping things simple here.)

Answer 1

PART A:

The length of the pulse is

PART B:

The diameter of the beam is

So, the radius of the beam is

The cross section area of the beam is

The power delivered is

So, the intensity of the pulse is

PART C:

The maximum electric field can be calculated usig the following relation

The maximum magnetic field can be calculated usig the following relation

PART D:

The wavelength of the wave is

Number of wavelength in one pulse is