Light propagation in deterministic aperiodic waveguide arrays
Пропагација светлости у детерминистичким апериодичним низовима таласовода
Докторанд
Lučić, Nemanja M.Ментор
Gvozdić, DejanЧланови комисије
Crnjanski, JasnaTimotijević, Dejan
Jakšić, Zoran
Petričević, Slobodan
Метаподаци
Приказ свих података о дисертацијиСажетак
Over the past two decades, the light transport properties in regular (periodic)
and disordered coupled waveguides have been extensively scrutinized. These two, in
a sense, opposite types of ordering lead to two dierent phenomena - discrete diraction
in regular arrays, where light energy spreads linearly along propagation direction,
and transverse localization in disordered, where light energy is distributed between
nite number of adjacent waveguides. Still an open question remains whether
light behavior in intermediate domain is between fully periodic and fully disordered
structures - deterministic structures with no periodicity.
In this thesis the impact of deterministic aperiodic one-dimensional (1D) and
two-dimensional (2D) coupled waveguide arrays (photonic lattices) on transverse
light transport has been investigated both experimentally and numerically. Several
types of lattices were considered: 1D and 2D position modulated Fibonacci lattices,
1D refractive index contrast modulate...d Fibonacci lattice, 1D regular lattice and
regular lattice with defect. The aim is to explore the possibility of using these
structures as a tool for light diraction suppression.
In the experiment, waveguide arrays were generated in photorefractive crystals,
lithium-niobate and strontium-barium-niobate, by direct laser writing and incoherent
Bessel beam induction technique, respectively. Gaussian and Airy beam were
used as excitation beams. A series of numerical simulations were conducted using
Beam Propagation Method.
It is found that the position modulated Fibonacci lattice can suppress light
diraction in comparison to the regular one. This is more pronounced in 1D than in
2D lattice. In 1D case, for relatively high refractive index contrasts, the propagating
beam becomes almost completely localized in transverse plane. In 1D refractive
index contrast modulated Fibonacci lattice the similar result is obtained - diraction
is suppressed considerably comparing to regular lattice. Furthermore, the stronger
modulation leads to strongly localized states, so the light propagation in Fibonacci
lattice resembles the propagation in disordered one. Besides, it is shown that the
slightly disordered Fibonacci lattice with relatively small refractive index contrast
modulation enhances diraction. In addition, it is shown that a regular lattice can
reduce a self-bending of Airy beam trajectory.
The research presented in the thesis provides additional standpoint in understanding
of light transport in complex optical structures and imposes new ways for
control of light diraction and engineering of the optical response of devices.
U prethodne dve decenije, prostiranje svetlosti u regularnim (periodič-
nim) i neuređenim spregnutim talasovodima je intenzivno proučavano. Ova
dva, na neki način suprotna tipa uređenja, odgovorna su za dva različita
fenomena - diskretnu difrakciju u regularnim nizovima, gde se energija svet-
losti širi linearno duž pravca propagacije, i transverzalnu lokalizaciju
u neuređenim nizovima, gde je svetlosna energija raspoređena u konačnom broju
susednih talasovoda. Još uvek je otvoreno pitanje ponašanja svetlosti u oblasti
između sasvim periodičnih i sasvim neuređenih struktura - determinističkim
strukturama bez periodičnosti.
U ovoj tezi je eksperimentalno i numerički proučavan uticaj determin-
ističkih aperiodičnih jednodimenzionih (1D) i dvodimenzionih (2D) nizova
spregnutih talasovoda (fotonskih rešetki) na transverzalnu propagaciju svet-
losti...