- #1

krhisjun

- 22

- 0

## Homework Statement

Im working on a lab experiment in my undergraduate physics degree requiring the use of a class 4 laser, i need to characterize this in terms of its power, coherence, pulse duration, wavelength and irradiance. This is a pulsed laser with rough parameters of 1-2J pulse energy, beam size at output - 2cm square, pulse duration ~ 100ns full width half maximum followed by a tail out to 1 ms, wavelngth 10-11 microns

I will be using a lens to focus the beam that has a focal length of approximatly 20cm

## Homework Equations

I could write an extensive list but ofcourse:

Gaussian lens formula, 1/f = 1/u + 1/v

Wo = df/ pi Wl

fluence - energy / area

irradiance = power/ area

Wo^2 = wavelength r / 2 pi

## The Attempt at a Solution

Im thinking of using a thermopile detector to measure the power of the beam and then perhaps a razor edge passing infront of the beam while still measuring the intensity so that i can calculate the area + profile of the beam? i would measure the total power in the beam when fully exposed then translate the knife edge across the beam and measure the distance between the points at which the power output is 10% and 90%, this will give 1.28 x 1/e^2 = diameter of the beam?

To measure the wavelength I am assuming I am going to use a spectrometer, using a flourescent strip illuminated with a UV light, then the heat from the laser kills the fluorescence after being split up into wavelength components via a diffraction grating..

The pulse duration I've been given a value for but how would i go about measuring this? some sort of fast detector?

To summarize I am looking for help with these methods, more information on them or alternative ideas, I am performing this later in the week and have been asked to do some preliminary calculations but I am not sure what I am supposed to be doing?

Cheers,

Khris