8 / 9
Page 28
allied
academies
August 23-24, 2018 | Paris, France
Laser, Optics and Photonics
International Conference on
Journal of Materials Science and Nanotechnology | Volume: 2
Simulating XY spin systems with coupled laser networks
Vishwa Pal
1
, Chene Tradonsky
2
, Ronen Chriki
2
, Asher A Friesem
2
and
Nir Davidson
2
1
Indian Institute of Technology Ropar, India
2
Weizmann Institute of Science, Israel
C
oupled lasers are useful for both applied and fundamental
research. It has been shown that a very large arrays
of >1000 lasers with nearest-neighbour coupling rapidly
dissipates into long range phase ordering, identical to the
ground state of a corresponding XY spin Hamiltonian. Finding
the ground state can be mapped to solve optimization
problems that are NP hard. Topological defects arise as a
result of spontaneous symmetry breaking, when a system
undergoes a phase transition from a complex disordered
phase state to an ordered phase state, known as Kibble
Zurek Mechanism (KZM). Because of topological protection
they become trapped in the system, therefore limits the
coherence of the system and its ability to approach a fully
ordered state. Revealing and controlling these topological
defects has been an important area of research in various
fields such as cosmology, spin systems, cold atoms and
optics. We investigated dissipative topological defects in a
one-dimensional ring network of coupled lasers and show
how their formation is related to the Kibble-Zurek (KZ)
mechanism. These defects may be topologically protected,
dependingon the sizeandgeometryof the system, preventing
it from reaching a perfect ordered state. We experimentally
found that the probability of topological defects increases
with the system size, and also strongly depends on various
laser parameters such as pump and coupling strengths.
We confirmed that the formation of topological defects is
governed by two competing time scales, namely phase
locking time and synchronization time of the lasers amplitude
fluctuations. More specifically, when the phase locking time
is smaller than the synchronization time, the probability
for topological defects formation is zero. Whereas, when
the phase locking time exceeds the synchronization time,
the probability for topological defects formation is finite.
Speaker Biography
Vishwa Pal joined Indian Institute of Technology Ropar, India, as an assistant professor
of Physics in May 2018. He received his PhD in 2014 from School of Physical Sciences,
Jawaharlal Nehru University, New Delhi, India. He has done part of his PhD at CNRS
Laboratories Aime Cotton, Orsay, France. During his PhD program, he investigated
semiconductor laser systems. After PhD, he received a 3-years PBC fellowship for
outstanding postdoctoral researcher by the Council for Higher Education of Israel. In 2018,
he joined CREOL, the College of Optics and Photonics, Florida, USA, as a research scientist
andworked on synthesizing non-diffracting optical beams in free space by exploiting space-
time correlations. In 2018, he also received Marie Sklodowska-Curie Actions Individual
Fellowship by European Commission.
e:
vishwa.pal@iitrpr.ac.inNotes: