# Chapter 9: Photonic Devices¶

## Example 9.1 Page 287¶

In [1]:
#initialisation of variable
from math import *
T=.25*10**-4;#thickness
E=3.00;#energy
P=10;#power
a=4*10**4#absorption coefficient
Eg=1.12;
q=1.6*10**-19;#charge

#calculation
Es=10**-2*(1-exp(-a*T));#energy absorbed per second
Ee=(E-Eg)/E;#photons energy converted to heat
L=Ee*Es;#energy to lattice
Ps=(Es-L)/(q*Eg);#photons per second

#result
print"energy absorbed per second is",round(Es*1000,1),"mW"
print"portion of photons energy converted to heat is",round(Ee*100,2),"%"
print"number of photons per second is",round(Ps,2),"photons/sec"

energy absorbed per second is 6.3 mW
portion of photons energy converted to heat is 62.67 %
number of photons per second is 1.31691783089e+16 photons/sec


## Example 9.2 Page 297¶

In [2]:
#initialisation of variable
from math import *
t=500*10**-12;#time

#calculation
f=1/(2*pi*t);#bandwidth

#result
print"modulation bandwidth is",round(f/10**6,0),"MHz"

modulation bandwidth is 318.0 MHz


## Example 9.3 Page 302¶

In [3]:
#initialisation of variable
from math import *
n=3.6;#constant

#calculation
R=((n-1)/(n+1))**2;#reflectivity

#result
print"reflected light is",round(R*100,0),"%"

reflected light is 32.0 %


## Example 9.4 Page 303¶

In [4]:
#initialisation of variable
from math import *
l=.94;#wavelength
n=3.6;
L=300;#length

#calculation
A=l**2/(2*n*L);#mode spacing

#result
print"mode spacing is",round(A*10**4,0),"angstron"

mode spacing is 4.0 angstron


## Example 9.5 Page 306¶

In [5]:
#initialisation of variable
from math import *
R1=.44;#front reflectivity
R2=.99;#rear reflectivity
L=300*10**-4;#length
W=5*10**-4;#width
a=100;#alpha
b=.1;#beta
g=100;
T=.9;#constant

#calculation
J=g*T/b+1/b*(a+1/(2*L)*log(1/(R1*R2)));#current density
I=J*L*W;#current

#result
print"current density is",round(J,2),"A/cm^2"
print"threshold current is",round(I*1000,2),"mA"

current density is 2038.51 A/cm^2
threshold current is 30.58 mA


## Example 9.6 Page 307¶

In [6]:
#initialisation of variable
from math import *
T1=27;#temperature
l=110;

#calculation
T=T1+l*log(2);#temperature

#result
print"temperature is",round(T,0),"deg.Celsius"

temperature is 103.0 deg.Celsius


## Example 9.7 Page 313¶

In [7]:
#initialisation of variable
from math import *
N=5*10**12;#photons/s
n=.8;#constant
u=2500;
E=5000;#V/cm
L=10*10**-4;#length
q=1.6*10**-19;#charge

#calculation
I=q*n*N*u*l*E/L;#photocurrent
G=u*l*E/L;#gain

#result
print"photocurrent is",round(I*10**6,2),"microAmp"
print"gain is",round(G,2)

photocurrent is 4.0 microAmp
gain is 6.25


## Example 9.8 Page 315¶

In [8]:
#initialisation of variable
from math import *
a=10**4;#cm^-1
R=.1;

#calculation
X=-1/a*log(1/(2*(1-R)));#depth

#result
print"dpeth for half power absorbed is",round(X,2),"micro-m"

dpeth for half power absorbed is 0.59 micro-m


## Example 9.9 Page 319¶

In [9]:
#initialisation of variable
from math import *
s=1.118;#m
h=1;#height

#calculation
M=(1+(s/h)**2)**.5;#air mass

#result
print"air mass is",round(M,2)

air mass is 1.5


## Example 9.10 Page 322¶

In [10]:
#initialisation of variable
from math import *
Vs=.35;#voltage
Is=1*10**-9;#current
Il=.1;#A
Vl=.026;#V

#calculation
Voc=Vl*log(Il/Is);#open-circuit voltage
P=-Is*Vs*(exp(Vs/Vl)-1)-(-Il*Vs);#power

#result
print"open-circuit voltage is",round(Voc,2),"V"
print"output power is",round(P,4),"W"

open-circuit voltage is 0.48 V
output power is 0.0348 W