fixing spatial filter example, ading very simple phaseplate example

examples/fft/phaseplate.py

+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+from __future__ import unicode_literals
+
+import matplotlib.pyplot as plt
+
+from pykat.optics.gaussian_beams import HG_mode, beam_param
+from pykat.optics.fft import *
+import numpy as np
+import scipy
+
+def main():
+    print("""
+    --------------------------------------------------------------
+    Example file for using PyKat http://www.gwoptics.org/pykat
+
+    Generate a HG11 mode from a HG00 mode with a simple
+    phase plate.
+    
+    Andreas Freise, 18.10.2016    
+    --------------------------------------------------------------
+    """)
+    plt.close('all')
+    # wavelength
+    Lambda = 1064.0E-9 
+    # distance to propagate/focal length of lens
+    D = 4
+
+    ######## Generate Grid stucture required for FFT propagation ####
+    xpoints = 512
+    ypoints = 512
+    xsize = 0.05
+    ysize = 0.05
+    # Apply offset such that the center of the beam lies in the
+    # center of a grid tile
+    xoffset = -0.5*xsize/xpoints
+    yoffset = -0.5*ysize/ypoints
+
+    shape = grid(xpoints, ypoints, xsize, ysize, xoffset, yoffset)
+    x = shape.xaxis
+    y = shape.yaxis
+
+    ######## Generates input beam ################
+    gx = beam_param(w0=2e-3, z=0)
+    gy = beam_param(w0=2e-3, z=0)
+    beam = HG_mode(gx,gy,0,0)
+    global field, laser
+    field = beam.Unm(x,y) 
+ 
+    ####### Apply phase plate #######################################
+
+    plate = np.ones([xpoints, ypoints])
+    plate[0:xpoints//2, 0:ypoints//2]=-1.0
+    plate[xpoints//2:xpoints, ypoints//2:ypoints]=-1.0
+    
+    field2 = field*plate;
+
+    ####### Propagates the field by FFT ##############################
+    field2 = FFT_propagate(field2,shape,Lambda,D,1) 
+
+
+    # maybe apply a thin lens
+    f=D
+    field2 = apply_thin_lens(field2, shape, Lambda, f) 
+    field2 = FFT_propagate(field2,shape,Lambda,D,1)
+    
+    midx=(xpoints)//2
+    midy=(ypoints)//2
+    off1=50
+    off2=50
+
+    # plot hand tuned for certain ranges and sizes, not automtically scaled
+    fig=plt.figure(110)
+    fig.clear()
+    plt.subplot(1, 3, 1)
+    plt.imshow(abs(field))
+    plt.xlim(midx-off1,midx+off1)
+    plt.ylim(midy-off1,midy+off1)
+    plt.draw()
+    plt.subplot(1, 3, 2)
+    plt.imshow(plate)
+    #pl.xlim(midx-off2,midx+off2)
+    #pl.ylim(midy-off2,midy+off2)
+    plt.draw()
+    plt.subplot(1, 3, 3)
+    plt.imshow(abs(field2))
+    plt.xlim(midx-off2,midx+off2)
+    plt.ylim(midy-off2,midy+off2)
+    plt.draw()
+    if in_ipython():
+        plt.show(block=0)
+    else:
+        plt.show(block=1)
+
+
+# testing if the script is run from within ipython
+def in_ipython():
+    try:
+        __IPYTHON__
+    except NameError:
+        return False
+    else:
+        return True
+
+if __name__ == '__main__':
+    main()
+

examples/fft/spatial_filter.py

@@ -3,14 +3,26 @@ from __future__ import division
 from __future__ import print_function
 from __future__ import unicode_literals
 
-import pylab as pl
+import matplotlib.pyplot as plt
 
-from pykat.optics.gaussian_beams import HG_beam, beam_param
+from pykat.optics.gaussian_beams import HG_mode, beam_param
 from pykat.optics.fft import *
 import numpy as np
 import scipy
 
 def main():
+    print("""
+    --------------------------------------------------------------
+    Example file for using PyKat http://www.gwoptics.org/pykat
+
+    Simple spatial filter to measure the mode content in a
+    Hermite Gauss beam
+    
+    Andreas Freise, 18.10.2016    
+    --------------------------------------------------------------
+    """)
+    plt.close('all')
+
     # wavelength
     Lambda = 1064.0E-9 
     # distance to propagate/focal length of lens
@@ -34,6 +46,7 @@ def main():
     xoffset = -0.5*xsize/xpoints
     yoffset = -0.5*ysize/ypoints
 
+    global shape
     shape = grid(xpoints, ypoints, xsize, ysize, xoffset, yoffset)
     x = shape.xaxis
     y = shape.yaxis
@@ -41,9 +54,9 @@ def main():
     ######## Generates a mixture of fields ################
     gx = beam_param(w0=2e-3, z=0)
     gy = beam_param(w0=2e-3, z=0)
-	beam = HG_beam(gx,gy,n1,m1)
+    beam = HG_mode(gx,gy,n1,m1)
     field1 = beam.Unm(x,y) 
-	beam2 = HG_beam(gx,gy,n2,m2)
+    beam2 = HG_mode(gx,gy,n2,m2)
     field2 = beam2.Unm(x,y) 
     global field, laser1, laser2
     field = np.sqrt(c1)*field1 + np.sqrt(c2)*field2
@@ -80,29 +93,29 @@ def main():
     print("c2 {0}, coef2 {1}, error {3} (raw output {2})".format(c2, pc2, coef2, np.abs(c2-pc2)))
 
     # plot hand tuned for certain ranges and sizes, not automtically scaled
-	fig=pl.figure(110)
+    fig=plt.figure(110)
     fig.clear()
     off1=xpoints/10
     off2=xpoints/6
-	pl.subplot(1, 3, 1)
-	pl.imshow(abs(field))
-	pl.xlim(midx-off1,midx+off1)
-	pl.ylim(midy-off1,midy+off1)
-	pl.draw()
-	pl.subplot(1, 3, 2)
-	pl.imshow(abs(laser1))
-	pl.xlim(midx-off2,midx+off2)
-	pl.ylim(midy-off2,midy+off2)
-	pl.draw()
-	pl.subplot(1, 3, 3)
-	pl.imshow(abs(laser2))
-	pl.xlim(midx-off2,midx+off2)
-	pl.ylim(midy-off2,midy+off2)
-	pl.draw()
+    plt.subplot(1, 3, 1)
+    plt.imshow(abs(field))
+    plt.xlim(midx-off1,midx+off1)
+    plt.ylim(midy-off1,midy+off1)
+    plt.draw()
+    plt.subplot(1, 3, 2)
+    plt.imshow(abs(laser1))
+    plt.xlim(midx-off2,midx+off2)
+    plt.ylim(midy-off2,midy+off2)
+    plt.draw()
+    plt.subplot(1, 3, 3)
+    plt.imshow(abs(laser2))
+    plt.xlim(midx-off2,midx+off2)
+    plt.ylim(midy-off2,midy+off2)
+    plt.draw()
     if in_ipython():
-		pl.show(block=0)
+        plt.show(block=0)
     else:
-		pl.show(block=1)
+        plt.show(block=1)
 
 
 # testing if the script is run from within ipython