# 11: Laser, holography and Fibre optics¶

## Example number 11.1, Page number 317¶

In [4]:
#importing modules
import math
from __future__ import division

#Variable declaration
n1=1.53;   #refractive index of core
n2=1.5;    #refractive index of cladding
lamda=1*10**-6;   #wavelength(m)

#Calculation
NA=math.sqrt((n1**2)-(n2**2));   #numerical aperture(m)
V=((2*math.pi*a)*NA)/lamda;      #normalised frequency
M=(V**2)/2;    #number of guided mode

#Result
print "normalised frequency is",round(V,2)
print "number of guided mode is",round(M)

normalised frequency is 94.72
number of guided mode is 4486.0


## Example number 11.2, Page number 317¶

In [7]:
#importing modules
import math
from __future__ import division

#Variable declaration
n1=1.53;   #refractive index of core
n2=1.5;    #refractive index of cladding
lamda=1*10**-6;   #wavelength(m)

#Calculation
NA=math.sqrt((n1**2)-(n2**2));   #numerical aperture(m)

#Result
print "core radius is less than",round(a*10**6,2),"micro m"

core radius is less than 1.27 micro m


## Example number 11.3, Page number 317¶

In [11]:
#importing modules
import math
from __future__ import division

#Variable declaration
NA=0.5;    #numerical aperture(m)
n1=1.54;   #refractive index of core

#Calculation
n2=math.sqrt((n1**2)-(NA**2));    #refractive index of cladding
n=(n1-n2)/n1;     #change in core cladding refractive index

#Result
print "refractive index of cladding is",round(n2,4)
print "change in core cladding refractive index is",round(n,4)

refractive index of cladding is 1.4566
change in core cladding refractive index is 0.0542


## Example number 11.4, Page number 318¶

In [13]:
#importing modules
import math
from __future__ import division

#Variable declaration
NA=0.5;    #numerical aperture(m)
n1=1.48;   #refractive index of core

#Calculation
n2=math.sqrt((n1**2)-(NA**2));    #refractive index of cladding

refractive index of cladding is 1.393