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Resources for this: http://ocw.mit.edu/courses/mechanical-engineering/2-71-optics-spring-2009/video-lectures/lecture-16-gratings-amplitude-and-phase-sinusoidal-and-binary/MIT2_71S09_lec16.pdf - Page 6 on Phase gratings



In [1]:

    
import numpy as np
%pylab
from numpy.fft import fft, fftshift









    



Using matplotlib backend: TkAgg
Populating the interactive namespace from numpy and matplotlib



In [2]:

    
n = 1.5
l = 780e-9
k = 2*pi/l
x = linspace(-300,300,600)*20e-6
L = 5000*l
s = 780e-9/10.0
m = k*(n-1)*s

#fieldout = np.exp(1j*m/2.0*sin(2*pi*x/L)) # a sinusoidal phase variation
noise = array([np.random.ranf() for i in x])
fieldout = np.exp(1j*m/2.0*noise)



In [3]:

    
plot(fftfreq(600,20e-6),np.abs(fft(fieldout)),".-")









    Out[3]:





[<matplotlib.lines.Line2D at 0x7f37e2f4e710>]



In [4]:

    
L









    Out[4]:





0.0039000000000000003

4 mm grating wavelength... with 1/10 wavelength variation. This is essentially the limit to the flatness of any glass optic.



In [5]:

    
from scipy.signal import spline_filter



In [6]:

    
smoothed = spline_filter(noise.reshape((600,1)),1)



In [7]:

    
plot(smoothed)









    Out[7]:





[<matplotlib.lines.Line2D at 0x7f37c632e2e8>]



In [8]:

    
plot(noise)









    Out[8]:





[<matplotlib.lines.Line2D at 0x7f37c6242e10>]



In [ ]: