Measuring the Orbital Angular Momentum of Light for Astronomy

187 Pages·2017·25.91 MB·English

The University of Sydney
School of Physics
2017
Measuring the Orbital Angular
Momentum of Light for Astronomy
Richard Neo
supervised by
Prof. Joss Bland-Hawthorn, Dr. Sergio Leon-Saval, and A. Prof. Gabriel Molina-Terriza
A thesis submitted in fulfilment of the requirements for the degree of
Doctor of Philosophy

i
Except where acknowledged in the customary manner, the
material presented in this thesis is, to the best of my knowl-
edge, original and has not been submitted in whole or part
for a degree in any university.
Richard Neo
ii
Acknowledgements
I preface this section with the admission that in the end there are far too many people who have
contributed to this thesis in ways perhaps that I have not even considered. I realize that I owe too
many thank yous and have not enough time or space to name them all so I hope these will suffice.
At the moment I am sitting behind my visiting researchers desk at Macquarie University. It is
Monday morning and barring some last minute discussions with Gabriel, there is one last section
of this thesis which remains to be written. As I wait for Gabriel to arrive, and my coffee to kick
in, now might be a good time to begin, at the beginning.
My Mum, Dad and my brother Eric have always given me their full support, not just through the
years of postgraduate study, but throughout the entirety of my study of physics and my entire life.
Thank you Mom and Dad, and Eric for always supporting my decisions and being there for me,
both in my honours year in 2012, and the four following years of my PhD. I am glad that this time
I got to include you in my acknowledgements. Thank you for the dinner waiting for me in the
oven at night. Thank you for always going out of your way to make my life as easy as possible.
Thank you for always keeping me in your thoughts. Thank you for your understanding and
patience. Thank you for your selfless love. To mum, you are always there for me, and I know that
whenever I have a problem, no matter how minor, your first reaction will always be to help. You
taught me that family is the most important thing and I hope that I can always be there for you
also. To Dad, your level headed advice and morals have always served me well. I know that you
have always understood me so I hope that you understand now how much grateful I am for you.
To Eric, I’m sorry I was so busy these last years but our time spent together means more to me
than you know. I am looking forward to sharing more of my life with you and Ryu from now on.
At the end of 2012 and the start of 2013 I had just finished my honours year studying non-linear
fibre optics and I had vowed never to study physics again, so it came as quite a shock when I
found myself applying for a PhD. I remember I started this PhD with a whirlwind meeting with
my soon-to-be supervisors Joss and Gabriel (Sergio would come later). That first meeting did
quite well in setting the tone of the next four years of my PhD: Joss was characteristically
brimming with energy and sparkling eyes. Gabriel, more measured, slowly walked me through
some basic concepts, giving me plenty of time to think and graciously providing the answer when
my own understanding failed1. Sergio, I’m sorry to say that I don’t remember the first time we
1Somethings never change.
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iv Acknowledgements
met2 but I do have a recollection of visiting Joel Carpenter with you to look at their OAM setup.
I know that without the guidance of you, my supervisors, I would be no nearer to completing my
PhD now than at that first meeting four years ago.
Thank you Joss for your invaluable advice and your boundless energy, enthusiasm and optimism. I
can’t remember the number of times I have gone into a meeting with you feeling burnt
out/wearied and left re-energized. I am grateful for your many emails always keeping an eye out
for opportunities for me, keeping abreast of the literature and hunting for interesting and relevant
papers. Thank you for giving me the opportunity to pursue this PhD and for putting your faith in
me for the last four years.
Thank you Sergio for being eager to get your hands dirty listening to the latest problem with my
data/instrument etc. Thank you for always offering me whatever instrument that you may have,
even if I don’t use it and it languishes at Macquarie University for months (or years...), and for
keeping a space for me at Sydney University. Thank you for always offering me your full support.
Thank you Gabriel for always making me laugh and always looking on the bright side of things.
Your door has always been open to me (even if you have not been on the other side of it) and
without your insights, suggestions, guidance and PATIENCE, this thesis would not have been
possible. Thank you for being an excellent mentor and friend3. In you I have found a model of the
physicist that all students studying physics should aspire to. Thank you for the past four years
Gabriel.
Despite the fact that I have spent the majority of my time during this PhD at Macquarie
University, so much so that I moved two kilometres down the road, I am not technically a student
of Macquarie University. I am a permanent fixture of the “visiting researchers” office, I do not
have a student/staff card and I do not possess a student account here. Despite this, I feel that
Macquarie University has been a second home to me during this time and for this, I have to give
thanks to my colleagues at Macquarie University (in no particular order): Nora, Alex, Xavier,
Xavier, Reese, Mathieu, Iftekher and Eugene. You have all made my time at Macquarie
particularly enjoyable and without you I am sure the time spent during these years would not
have passed quite so quickly.
Coming into this PhD from a different field of research, I spent the first year learning the basics of
free space optics in the lab together with Eugene Tan. Thank you for making my first year of my
PhD one of the most enjoyable. I’ll always look back fondly on our days in the lab4, having lunch
together5 and your words of wisdom. I don’t think I have laughed as hard in the lab since my time
with you. I hope you’re doing well ET!
During these years working on my PhD, when I have not been in the lab, at my desk or sleeping,
if you were to guess that I was either dancing salsa, listening to salsa music, or watching salsa
videos, you would most likely be correct. Thank you to everyone who I have had the pleasure of
dancing with. Without knowing it, you have all helped me get through my PhD a healthier and
2I hope I haven’t accidentally erased you from that first meeting...
3I swear I will return your comics to you.
4Especially our discussions on Associate Professors, and your rendition of your own theme song.
5I have never known anyone who has eaten as much laksa as you ate during that year. A quick calculation puts
the number at approximately 250 bowls.
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happier person. Thank you to Becky for your guidance, and genuine care6.
Finally I would like to acknowledge you Giulia however, before that I have one confession to make
to you: I realize now that “Geometric phase Interferometer Utilizing Lights Angular
momentum” (GIULIA) would not be a particularly accurate acronym for the instrument developed
in this thesis and I regret is that I could not find another similar acronym which fits better7.
I would like to thank my best friend, and partner Giulia for her endless support and
understanding, love and devotion, and her genuine interest in the work which has defined the last
four years of my life. Without you, this thesis, as well as myself, would not exist in it’s current
form. Thank you for being you. Your love and encouragement has made all the difference in the
world to me and made it easier for me to go back into work after a challenging day. Your sound
advice has never let me down, and I’ve always been better for having listened to you8. The best
thing to happen to me during my PhD was meeting you Giulia and sometimes I am still struck
with wonder that I ended up with you.
The entire time you have known me, I have been working on this PhD and now this has come to
an end. I cannot wait for a new beginning with you.
6As well as understanding when my pesky PhD work intrudes on my training.
7If one were to replace the refractive modesorter in the interferometer described in Chapter 7, with a
Pancharatnam-Berry optical element sorter, then the resulting instrument would be more accurately described by
GIULIA.
8Even if it’s not what I wanted to hear.
vi Acknowledgements
List of Publications
[A] Neo, R., Tan, S. J., Zambrana-Puyalto, X., Leon-Saval, S., Bland-Hawthorn, J., &
Molina-Terriza, G. “Correcting vortex splitting in higher order vortex beams”. Optics
express, 22(8), 9920-9931 (2014).
[B] Neo, R., Goodwin, M., Zheng, J., Lawrence, J., Leon-Saval, S., Bland-Hawthorn, J., &
Molina-Terriza, G. “Measurement and limitations of optical orbital angular momentum
through corrected atmospheric turbulence”. Optics express, 24(3), 2919-2930 (2016).
[C] Neo, R., Molina-Terriza, G., & Twamley, J. “Lost, found and useful: Applications of Angular
Momentum sorting as optical Mellin transforms”. (In preparation).
[D] Neo, R., Leon-Saval, S., Bland-Hawthorn, J., & Molina-Terriza, G. “OAM observations of
the solar surface”. (In preparation).
[E] Neo, R., Leon-Saval, S., Bland-Hawthorn, J., & Molina-Terriza, G. “OAM interferometry:
the detection of the rotational Doppler shift”. Optics express, 25(18), 21159-21170 (2017).
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viii Acknowledgements