Performing the real lab:
 Arrange the laser and detector in an optical bench arrangement.
 The laser is switched on and is made to incident on the photodiode.
 Fix the distance, z between the detector and the laser source.
 By adjusting the micrometer of the detector, move the spot in the horizontal direction, from left to right.
 Note the output current for each distance, x from the measuring device.
 Then the beam profile is plotted with the micrometer distance along the Xaxis and intensity of current along Yaxis. We will get a gaussian curve (see Fig.1).
Fig.1 beam profile of Laser beam divergence.
 The experiment is repeated for different detector distances.
 Note the points in the graph where the intensity equals 1/e^{2} of the maximum intensity, say it as I_{e }(see Fig.1).
 Find the micrometer distance across the beam corresponding to these points ( BA from the Fig.1) for a pair of detector distances z_{1} and z_{2}. Half of this distance is noted as w_{1}and w_{2}.
 Then the divergence and spot size of the laser beam can be calculated from the equations.
Observation and calculation
To find the Least Count of Screw gauge
One pitchscale division ( n) = .............. mm
Number of divisions on head scale (m) = ...............
Least Count (L.C) = n/m = ......................
z_{1} = ....................... cm 
z_{2} = ................ cm 


1/e^{2} of maximum intensity,Ie =................ mA
Diameter of the beam corresponds to I_{e, } d_{1}= ..................mm

1/e^{2} of maximum intensity,Ie =................ mA
Diameter of the beam corresponds to I_{e, } d_{2}= ..................mm

Divergence angle(Θ) = (d_{2}d_{1})/(z_{2}z_{1}) = ........................ mrad
Performing the simulator:
 The experimental arrangement is shown in the simulator. A side view and top view of the set up is given in the inset.
 The start button enables the user to start the experiment.
 From the combo box, select the desired laser source.
 Then fix a detector distance, say 100 cm, using the slider Detector distance, z.
 The z distance can be varied from 50 cm to 200 cm.
 For a particular z distance, change the detector distance x, from minimum to maximum, using the slider Detector distance, x. The micrometer distances and the corresponding output currents are noted. The x distances can be read from the zoomed view of the micrometer and the current can be note from the digital display of the output device.
 Draw the graph and calculate the beam divergence and spot size using the steps given above.
 Show graph button enables the user to view the beam profile.
 Using the option Show result, one can verify the result obtained after doing the experiment.