Advanced

Tunable diode laser frequency stabilization and its applications in temperature measurement

Rabbani, Ali LU (2015) FYSM60 20151
Combustion Physics
Department of Physics
Abstract
The frequency of two external cavity diode lasers tuned to the two transitions at
410 nm and 451 nm of indium are stabilized in this thesis. A hollow cathode lamp of
indium atoms is used as a low pressure source of indium atoms in the locking process.
Two frequency stabilization methods, wavelength modulation spectroscopy (WMS) and
polarization spectroscopy (PS), are used in the thesis for the laser locking. In both
methods a computer generated sweeping current is sent to a diode laser to produce a
wavelength scan around a resonant transition of indium. The laser passes through the
lamp and recorded on a photodiode. The recorded signal will be transferred to a computer
program. The program, in the case of wavelength modulation... (More)
The frequency of two external cavity diode lasers tuned to the two transitions at
410 nm and 451 nm of indium are stabilized in this thesis. A hollow cathode lamp of
indium atoms is used as a low pressure source of indium atoms in the locking process.
Two frequency stabilization methods, wavelength modulation spectroscopy (WMS) and
polarization spectroscopy (PS), are used in the thesis for the laser locking. In both
methods a computer generated sweeping current is sent to a diode laser to produce a
wavelength scan around a resonant transition of indium. The laser passes through the
lamp and recorded on a photodiode. The recorded signal will be transferred to a computer
program. The program, in the case of wavelength modulation spectroscopy locking
technique, reduces the scanning range in order to lock the laser to the transitions of
indium atoms. The polarization spectroscopy locking program sets the diode laser
frequency to the specified transition of indium atoms to lock the laser.
The frequency stabilized lasers are used to conduct temperature measurements in
an indium seeded flame with two-line atomic fluorescence. A flow of nitrogen gas seeds
trimethylindium molecules to the flame and the exothermic combustion processes in the
flame breaks the trimethylindium molecule bonds to produce free indium atoms. Two
line atomic fluorescence thermometry technique is used to measure the temperature of the
flame. A thin sheet of a stabilized diode laser is used to excite indium atoms.
Frequency stabilization of the two lasers was done within 250 MHz for WMS and
110 MHz for PS allowing for high precision temperature measurements. The preliminary
temperature measurements showed great potential for future measurements in
combustion environments. (Less)
Popular Abstract
At a first glance stabilized continuous wave laser seems to have no use in
everyday life, but its application in technologies like the global positioning system (GPS)
is an essential part of modern life. Continuous wave lasers are also widely used in many
different spectroscopic techniques; make it possible to analyze the material in order to
improve our understanding of the surrounding environment. By choosing the correct
color of the laser t specific species can be made to emit fluorescence signals, these
fluorescence signal may be used as a fingerprint to detect the specie or measure the
characteristics of the specific specie. The wavelength required for an atom to be excited
is called a transition wavelength. By stabilizing the... (More)
At a first glance stabilized continuous wave laser seems to have no use in
everyday life, but its application in technologies like the global positioning system (GPS)
is an essential part of modern life. Continuous wave lasers are also widely used in many
different spectroscopic techniques; make it possible to analyze the material in order to
improve our understanding of the surrounding environment. By choosing the correct
color of the laser t specific species can be made to emit fluorescence signals, these
fluorescence signal may be used as a fingerprint to detect the specie or measure the
characteristics of the specific specie. The wavelength required for an atom to be excited
is called a transition wavelength. By stabilizing the laser to an atomic transition
wavelength the resulting fluorescence can be continuously monitored.
In this thesis two spectroscopic methods are used to stabilize tunable diode lasers
to transitions of indium atoms, wavelength modulation spectroscopy and polarization
spectroscopy. The source of indium atoms used for frequency stabilization is a hollow
cathode lamp. Hollow cathode lamp produces indium atoms in a low pressure
environment so indium atoms are less likely to collide with each other or the container
surface. Depending on the amount of exchanged energy by collisions; atoms absorb or
emit different frequencies. Low pressure environment reduces the atom collisions
therefore reduces the variation in the absorbed or emitted frequency of atoms.
The wavelength modulation spectroscopy technique is a variation of absorption
spectroscopy with higher signal to noise ratio compare to the normal absorption
spectroscopy. The wavelength modulation spectroscopy frequency stabilization technique
stabilizes the diode laser frequency in a range of several hundred megahertz around the
absorption frequency of transition. (Less)
Please use this url to cite or link to this publication:
author
Rabbani, Ali LU
supervisor
organization
course
FYSM60 20151
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Temperature measurements, Frequency stabilization
language
English
id
8058331
date added to LUP
2015-10-19 16:40:09
date last changed
2015-10-19 16:40:09
@misc{8058331,
  abstract     = {The frequency of two external cavity diode lasers tuned to the two transitions at
410 nm and 451 nm of indium are stabilized in this thesis. A hollow cathode lamp of
indium atoms is used as a low pressure source of indium atoms in the locking process.
Two frequency stabilization methods, wavelength modulation spectroscopy (WMS) and
polarization spectroscopy (PS), are used in the thesis for the laser locking. In both
methods a computer generated sweeping current is sent to a diode laser to produce a
wavelength scan around a resonant transition of indium. The laser passes through the
lamp and recorded on a photodiode. The recorded signal will be transferred to a computer
program. The program, in the case of wavelength modulation spectroscopy locking
technique, reduces the scanning range in order to lock the laser to the transitions of
indium atoms. The polarization spectroscopy locking program sets the diode laser
frequency to the specified transition of indium atoms to lock the laser.
The frequency stabilized lasers are used to conduct temperature measurements in
an indium seeded flame with two-line atomic fluorescence. A flow of nitrogen gas seeds
trimethylindium molecules to the flame and the exothermic combustion processes in the
flame breaks the trimethylindium molecule bonds to produce free indium atoms. Two
line atomic fluorescence thermometry technique is used to measure the temperature of the
flame. A thin sheet of a stabilized diode laser is used to excite indium atoms.
Frequency stabilization of the two lasers was done within 250 MHz for WMS and
110 MHz for PS allowing for high precision temperature measurements. The preliminary
temperature measurements showed great potential for future measurements in
combustion environments.},
  author       = {Rabbani, Ali},
  keyword      = {Temperature measurements,Frequency stabilization},
  language     = {eng},
  note         = {Student Paper},
  title        = {Tunable diode laser frequency stabilization and its applications in temperature measurement},
  year         = {2015},
}