Nonequilibrium Bose condensation in a
pumped dye-filled photonic cavity
vorgelegt von
M. Sc.
Martina Vlaho
ORCID: 0000-0002-1214-6790
an der Fakultät II ś Mathematik und Naturwissenschaften
der Technischen Universität Berlin
zur Erlangung des akademischen Grades
Doctor rerum naturalium
- Dr. rer. nat.-
genehmigte Dissertation
Promotionsausschuss:
Vorsitzender: Prof. Dr. Markus R. Wagner
Gutachter: Prof. Dr. André Eckardt
Gutachter: Prof. Dr. Jonas Ola Oscar Larson
Tag der wissenschaftlichen Aussprache: 22. April 2022
Berlin 2022
iii
Declaration of Authorship
I declare that this thesis is my own work and has not been submitted to this or any other
academic institution for any other degree or qualification.
Chapters 4through 6are adapted from my published papers (referenced in the chapters)
and all the writing, calculations and figure production was done by me.
I declare that I have acknowledged all main sources of help and appropriately referenced
the published work of others.
v
TECHNISCHE UNIVERSITÄT BERLIN
Abstract
Faculty II - Mathematics and Natural Sciences
Institute for Theoretical Physics
Nonequilibrium Bose condensation in a pumped dye-filled photonic cavity
by Martina Vlaho
An effectively two-dimensional photon gas trapped in a dye-filled microcavity can un-
dergo thermalization and equilibrium-like Bose-Einstein condensation. However, given
the inherently driven-dissipative nature of this system, it can exhibit a complex interplay
between the thermalizing influence of the environment given by the dye solution and the
pump and loss processes driving the system out of equilibrium. We first consider a ho-
mogeneously pumped photon gas and investigate how its steady state is affected when
varying the pump power, the cavity lifetime and the cutoff frequency. Depending on the
parameter regime, the selection of modes that acquire large occupation can be related ei-
ther to lasing of (typically multiple) modes or to a quasiequilibrium condensation in the
ground state. We calculate and explain the phase diagram of the system, with a particular
emphasis on the role played by mode competition that occurs in the regime of weak cavity
loss. We then consider the case where the system is driven asymmetrically (by a relatively
narrow off-centered pump beam) and find that it features a robust and controllable mech-
anism for two-mode emission. Namely, after the system starts lasing in the dominantly
pumped excited mode, in a second transition a photon condensate is formed in the ground
mode, when the pump power is increased further. This effect is a consequence of the redis-
tribution of excited dye molecules via the lasing mode in combination with thermalization.
We demonstrate how this effect can be controlled further by tailoring the effective trans-
verse potential for the photons. This allows for the threshold pump power to be tuned
by orders of magnitude. For this scenario we formulate a simplified, analytically solvable
model which gives a very good agreement, both qualitative and quantitative, with the full
original model.
Loading more pages...