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{
"metadata": {
"name": "",
"signature": "sha256:c3dcf79a03b4887493b03eb7567c9289353e41ba9f42b1e11e4742e5d995690d"
},
"nbformat": 3,
"nbformat_minor": 0,
"worksheets": [
{
"cells": [
{
"cell_type": "heading",
"level": 1,
"metadata": {},
"source": [
"11: Laser"
]
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example number 11.1, Page number 33"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#importing modules\n",
"import math\n",
"from __future__ import division\n",
"\n",
"#Variable declaration\n",
"lamda=590*10**-9; #wavelength of sodium D line(m)\n",
"h=6.626*10**-34; #planck's constant\n",
"c=3*10**8; #velocity of light(m/s)\n",
"e=1.602*10**-19; #charge of electron(eV)\n",
"\n",
"#Calculation\n",
"E=h*c/lamda; #energy of 1st excited state(J)\n",
"E=E/e; #energy of 1st excited state(eV)\n",
"\n",
"#Result\n",
"print \"energy of 1st excited state is\",round(E,1),\"eV\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"energy of 1st excited state is 2.1 eV\n"
]
}
],
"prompt_number": 2
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example number 11.2, Page number 34"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#importing modules\n",
"import math\n",
"from __future__ import division\n",
"\n",
"#Variable declaration\n",
"T=250+273; #temperature(K)\n",
"lamda=590*10**-9; #wavelength of sodium D line(m)\n",
"h=6.626*10**-34; #planck's constant\n",
"c=3*10**8; #velocity of light(m/s)\n",
"k=1.38*10**-23; #boltzmann constant\n",
"\n",
"#Calculation\n",
"a=h*c/(k*T*lamda);\n",
"N2byN1=math.exp(-a); #ratio between atoms in 1st excited state and ground state\n",
"\n",
"#Result\n",
"print \"ratio between atoms in 1st excited state and ground state is\",round(N2byN1*10**21,2),\"*10**-21\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"ratio between atoms in 1st excited state and ground state is 5.33 *10**-21\n"
]
}
],
"prompt_number": 6
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example number 11.3, Page number 34"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#importing modules\n",
"import math\n",
"from __future__ import division\n",
"\n",
"#Variable declaration\n",
"T=250+273; #temperature(K)\n",
"lamda=590*10**-9; #wavelength of sodium D line(m)\n",
"h=6.626*10**-34; #planck's constant\n",
"c=3*10**8; #velocity of light(m/s)\n",
"k=1.38*10**-23; #boltzmann constant\n",
"\n",
"#Calculation\n",
"a=h*c/(k*T*lamda);\n",
"N2byN1=1/(math.exp(a)-1); #ratio between stimulated emission and spontaneous emission\n",
"\n",
"#Result\n",
"print \"ratio between stimulated emission and spontaneous emission is\",round(N2byN1*10**21,4),\"*10**-21\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"ratio between stimulated emission and spontaneous emission is 5.3298 *10**-21\n"
]
}
],
"prompt_number": 8
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example number 11.4, Page number 35"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#importing modules\n",
"import math\n",
"from __future__ import division\n",
"\n",
"#Variable declaration\n",
"n0=1.76; #refractive index of ruby rod\n",
"new0=4.3*10**14; #frequency(Hz)\n",
"deltav0=1.5*10**11; #doppler broadening(Hz)\n",
"c=3*10**8; #velocity of light(m/s)\n",
"tow21=4.3*10**-3; #lifetime of spontaneous emission(s)\n",
"tow_photon=6*10**-9; #lifetime of photon(s)\n",
"\n",
"#Calculation\n",
"a=4*math.pi**2*new0**2*n0**3/(c**3);\n",
"N2_N1=a*tow21*deltav0/tow_photon; #difference between excited state and ground state population(per m**3)\n",
"\n",
"#Result\n",
"print \"difference between excited state and ground state population is\",round(N2_N1*10**-23,3),\"*10**23 per m**3\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"difference between excited state and ground state population is 1.584 *10**23 per m**3\n"
]
}
],
"prompt_number": 10
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example number 11.5, Page number 35"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#importing modules\n",
"import math\n",
"from __future__ import division\n",
"\n",
"#Variable declaration\n",
"T=300; #temperature(K)\n",
"lamda=5000*10**-10; #wavelength of light(m)\n",
"h=6.626*10**-34; #planck's constant\n",
"c=3*10**8; #velocity of light(m/s)\n",
"k=1.38*10**-23; #boltzmann constant\n",
"\n",
"#Calculation\n",
"a=h*c/(k*T*lamda);\n",
"N2byN1=1/(math.exp(a)-1); #ratio between stimulated emission and spontaneous emission\n",
"\n",
"#Result\n",
"print \"ratio between stimulated emission and spontaneous emission is\",round(N2byN1*10**42),\"*10**-42\"\n",
"print \"answer varies due to rounding off errors\"\n",
"print \"spontaneous emission is more predominant than that of stimulated emission. for stimulating emission, N2>>N1. therefore there is no amplification possibility\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"ratio between stimulated emission and spontaneous emission is 2.0 *10**-42\n",
"answer varies due to rounding off errors\n",
"spontaneous emission is more predominant than that of stimulated emission. for stimulating emission, N2>>N1. therefore there is no amplification possibility\n"
]
}
],
"prompt_number": 13
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example number 11.6, Page number 36"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"#importing modules\n",
"import math\n",
"from __future__ import division\n",
"\n",
"#Variable declaration\n",
"lamda=632.8*10**-9; #wavelength of laser beam(m)\n",
"h=6.626*10**-34; #planck's constant\n",
"c=3*10**8; #velocity of light(m/s)\n",
"P=2.3*10**-3; #output power(W)\n",
"\n",
"#Calculation\n",
"new=c/lamda; #frequency of photon(Hz)\n",
"E=h*new; #energy of photon(J)\n",
"El=P*60; #energy emitted by laser(J/min)\n",
"n=El/E; #number of photons emitted(photons/min)\n",
"\n",
"#Result\n",
"print \"number of photons emitted is\",round(n*10**-17,3),\"*10**17 photons/min\"\n",
"print \"answer varies due to rounding off errors\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"number of photons emitted is 4.393 *10**17 photons/min\n",
"answer varies due to rounding off errors\n"
]
}
],
"prompt_number": 22
}
],
"metadata": {}
}
]
}
|
