# Ch-5 Optical Detector¶

## Example 5.24 Page no 487¶

In [16]:
from __future__ import division
from math import sqrt, pi

# Calculation of (a) wavelength (b) resposivity and (c) incident power

#Given data
e=0.7#                      # Efficiency
c=3*10**8#                   # Speed   of light
h=6.62*10**-34               # Planck constant
E=2.2*10**-19#               # Energy of photons
e1=1.6*10**-19#              # Electron charge
# (a) Wavelength computation
lamda=h*c/E                # Wavelength of laser source
f=c/lamda#

# (b) Responsivity
R=e*(lamda*e1)/(h*c)#

# (c) Incident power
Ip=2*10**-6#                  # Photocurrent
P=Ip/R#

print"Wavelength of operation = %0.1f micrometer "%(lamda*10**6)#
print"Responsivity R = %0.2f A/W "%(R)#
print"output power P = %0.2f microwWatt "%(P*10**6)#

Wavelength of operation = 0.9 micrometer
Responsivity R = 0.51 A/W
output power P = 3.93 microwWatt


## Example 5.25 Page no 487¶

In [17]:
# Computation of (a) quantum efficiency and (b) resposivity

#Given data
nh=1.5*10**12#                 # No. of hole pairs generated
np=2.5*10**12#                 # No. of incident photons
lamda=0.85*10**-6#            # Wavelength of laser source
c=3*10**8#                     # Speed of light
h=6.62*10**-34                 # Planck constant
e1=1.6*10**-19#                # Electronic charge

# (a)  Quantum efficiency
e=nh/np#

# (b) Responsivity
R=e*(lamda*e1)/(h*c)#                       #

print"Quantum efficiency = %0.1f  "%(e)#
print"Responsivity R = %0.3f A/W "%(R)#

Quantum efficiency = 0.6
Responsivity R = 0.411 A/W


## Example 5.26 Page no 488¶

In [18]:
# Computation of (a) wavelength (b) power and (c) resposivity

#Given data
e=0.7#                     # Quantum efficiency
c=3*10**8#                  # Speed of light
h=6.62*10**-34              # Planck constant
E=1.5*10**-19#              # Energy of photons
e1=1.6*10**-19#             # Electronic charge
I=4*10**-6#                 # Diode photocurrent
# (a) Wavelength of operation
lamda=h*c/E#

# (b) Responsivity
R=e*(lamda*e1)/(h*c)#                       #

# (c) Incident optical power
p=I/R#                                #power

print"Wavelength of operation = %0.3f micrometer "%(lamda*10**6)#
print"Responsivity R = %0.3f A/W "%(R)#
print"output power P = %0.3f microwWatt "%(p*10**6)#

Wavelength of operation = 1.324 micrometer
Responsivity R = 0.747 A/W
output power P = 5.357 microwWatt


## Example 5.27 Page no 488¶

In [19]:
# Computation of (a)resposivity (b)output current and (c)multiplication factor

#Given data
e=0.7#                  # Quantum efficiency
c=3*10**8#               # Speed of light
h=6.62*10**-34           # Planck constant
E=1.5*10**-19#           # Energy of photons
lamda=0.85*10**-6       # Wavelength of laser source
P=0.6*10**-6#            # Incident light power
e1=1.6*10**-19#          # Electronic charge
I=10*10**-6#             # Output current of the device

# (a) Responsivity
R=e*(lamda*e1)/(h*c)#

# (b) Photocurrent
Ip=R*P#

# (c) Multiplication factor
M=I/Ip

print"Responsivity R = %0.3f A/W "%(R)#
print"Output current Ip = %0.3f microA "%(Ip*10**6)#
print"Multiplication factor M = %0.0f  "%(M)#

#Calculation mistake in (b)Phtocurrent in the book

Responsivity R = 0.479 A/W
Output current Ip = 0.288 microA
Multiplication factor M = 35


## Example 5.28 Page no 488¶

In [20]:
# Computation of  cut off wavelength

# Given data
h=6.626*10**-34#          # Planck constant.
c=3*10**8#                # Speed of light
Eg= 1.43*1.602*10**-19#   # Bandgap energy

# Cut off wavelength
lamda= h*c/Eg#

print"Cut off wavelength = %0.3f micrometer "%(lamda*10**6)#

Cut off wavelength = 0.868 micrometer


## Example 5.29 Page no 489¶

In [21]:
# Computation of cut off wavelength

# Given data
h=6.626*10**-34#            # Planck constant
c=3*10**8#                  # Speed of light
Eg= 0.7*1.602*10**-19#      # Bandgap energy

# Cut off wavelength
lamda= h*c/Eg#

print"Cut off wavelength = %0.2f micrometer "%(lamda*10**6)#

Cut off wavelength = 1.77 micrometer


## Example 5.30 Page no 489¶

In [22]:
# Computation of value of reflectance

# Given data
n1=3.5#                  # Refractive index of silicon
n2=1#                    # Refractive index of photodiode

#Value of reflectance
R=((n1-n2)/(n1+n2))**2#

print"Value of reflectance, R = %0.2f  "%(R)#

Value of reflectance, R = 0.31