# chapter6 - Optical sources¶

## Example 6.3.1, page 6-7¶

In :
from __future__ import division
x=0.07
Eg=1.424+1.266*x+0.266*x**2
lamda=1.24/Eg       #computing wavelength
print "Wavlength is %.3f micrometer." %lamda

Wavlength is 0.819 micrometer.


## Example 6.3.2, page 6.12¶

In :
n=1.7       #refractive index
L=5*10**-2      #distance between mirror
c=3*10**8       #speed of light
lamda=0.45*10**-6   #wavelength
k=2*n*L/lamda       #computing number of modes
delf=c/(2*n*L)      #computing mode separation
delf=delf*10**-9
print "Number of modes are %.2e.\nFrequency separation is %.2f GHz."%(k,delf)

Number of modes are 3.78e+05.
Frequency separation is 1.76 GHz.


## Example 6.7.1, page 6-26¶

In :
from __future__ import division
h=6.624*10**-34   #plank's constant
c=3*10**8       #speed of light
q=1.6*10**-19   #charge of electron
i=35*10**-3     #current
lamda=0.85*10**-6       #wavelength
t=tr*tnr/(tr+tnr)           #computing total recombination time
eta=t/tr                    #computing internal quantum efficiency
Pint=eta*h*c*i/(q*lamda)    #computing internally generated power
Pint=Pint*10**3
print "Total recombinaiton time is %.2f ns.\nInternal quantum efficiency is %.3f.\nInternally generated power is %.2f mW." %(t,eta,Pint)
#answer in the book for Internal quantum efficiency & Internally generated power is wrong.

Total recombinaiton time is 31.48 ns.
Internal quantum efficiency is 0.630.
Internally generated power is 32.20 mW.


## Example 6.8.1, page 6-34¶

In :
from numpy import sqrt, pi
f1=10*10**6     #frequency
f2=100*10**6
t=4*10**-9
Pdc=280*10**-6      #optincal output power
w1=2*pi*f1     #computing omega
Pout1=Pdc*10**6/(sqrt(1+(w1*t)**2))       #computing output power
w2=2*pi*f2     #computing omega
Pout2=Pdc*10**6/(sqrt(1+(w2*t)**2))       #computing output power
print """Ouput power at 10 MHz is %.2f microwatt.
Ouput power at 100 MHz is %.2f microwatt.
Conclusion when device is drive at higher frequency the optical power reduces.""" %(Pout1,Pout2)
BWopt = sqrt(3)/(2*pi*t)
BWelec = BWopt/sqrt(2)
BWopt=BWopt*10**-6
BWelec=BWelec*10**-6
print "3 dB optical power is %.2f MHz.\n3 dB electrical power is %.2f MHz." %(BWopt,BWelec)
#calculation error. In the book square term in the denominater is not taken.
#answers in the book are wrong.

Ouput power at 10 MHz is 271.55 microwatt.
Ouput power at 100 MHz is 103.52 microwatt.
Conclusion when device is drive at higher frequency the optical power reduces.
3 dB optical power is 68.92 MHz.
3 dB electrical power is 48.73 MHz.


## Example 6.8.2, page 6-35¶

In :
n1=3.5   #refractive index
n=1     #refractive index of air
F=0.69  #transmission factor
eta = 100*(n1*(n1+1)**2)**-1      #computing eta
print "eta external is %.1f percent i.e. small fraction of intrnally generated opticalpower is emitted from the device." %eta
r= 100*F*n**2/(4*n1**2)       #computing ratio of Popt/Pint
print "Popt/Pint is %.1f percent" %r

eta external is 1.4 percent i.e. small fraction of intrnally generated opticalpower is emitted from the device.
Popt/Pint is 1.4 percent


## Example 6.8.3, page 6-39¶

In :
from numpy import log, exp
beta0=1.85*10**7
T=293       #temperature
k=1.38*10**-23  #Boltzman constant
Ea=0.9*1.6*10**-19
theta=0.65  #thershold
betar=beta0*exp(-Ea/(k*T))
t=-log(theta)/betar
print "Degradation rate is %.1e per hour.\nOperating lifetime is %.1e hour." %(betar,t)

Degradation rate is 6.3e-09 per hour.