232
8 Conclusion and Outlook
benefit from advances in the field of functionalised nanomaterials, and light–matter
coupling phenomena. It is also worth noting that, among many pathways to the
use of novel materials for photonics, the employment of optical microcavities in
combination with quantum materials has become very attractive for cavity quantumelectrodynamics studies and nanophotonics, which nowadays go beyond the use of
common semiconductor materials and epitaxially-grown quantum structures. Such
concepts are for instance subject of the research activities jointly performed by the
author with partners from the Zhejiang University, Hangzhou, with eyes towards
efficient quantum emitters for future quantum communication purposes. The principal investigators performed, both, jointly and individually scientific activities to
identify new application potentials of 2D materials, as well as zero-dimensional
structures, and to investigate light–matter interactions as well as a variety of novel
materials in optical cavities. For instance, the author explored concepts to smoothly
tune the coupling regime from weak to strong across the exceptional point. Also, a
new approach was targeted to deliver good enough optical microresonators based on
fibre technologies and high-reflectivity interfaces for efficient in- and out-coupling
of signal from flexible and tunable light–matter-coupled systems, as produced and
studied in the Hangzhou nanophotonics laboratories and further investigated in Marburg. In addition, to bring 2D semiconductors closer to applications and to improve
the emission properties, photoluminescence (PL) enhancement was recently studied
using WS 2 on nano-fabricated optical microresonators, which are achieved from ring
patterns (in-plane Bragg gratings) in a dielectric substrate. This approach pursued
for controlled emission rates and profiles by the author, and jointly published with
co-workers from Frankfurt, Hangzhou, and Marburg, allows combining both vertical
and horizontal interference effects to improve both in-coupling into and out-coupling
of light from 2D materials. Such structures could be at the core of future on-chip
optical interconnects for light-based information processing purposes. Photodetectors, photovoltaics, nonlinear optics and light-emitting diodes involving 2D materials
could strongly benefit from these advances for the concept introduced.
In the context of strong light–matter interactions, polariton physics offers an exciting playground for the study of Bose–Einstein-like condensation phenomena, as well
as the related effects, such as superfluidity. Employing 2D materials in this domain
has further enriched the field due to spin- and valley-sensitivity of TMDCs. The
manipulation and control of hybrid quantum states in matter with external photons is
an interesting direction to continue polariton research, after having studied various
examples of polariton condensates, their generation and their correlations. Studies
by the author on polaritons and excitons in external fields were deepened in the past
years as summarised in this work.
Other international and domestic collaborations have so far enabled effective studies on semiconductor disk lasers, for instance with regard to the self-mode-locking
effect and performance boosts for single-frequency or THz-generating devices, as
well as on material spectroscopy and quantum optics. In one case, a record flux
from a single-photon source was achieved by combining self-built pulsed lasers with
quantum emitters from Berlin, Germany.
8 Conclusion and Outlook
benefit from advances in the field of functionalised nanomaterials, and light–matter
coupling phenomena. It is also worth noting that, among many pathways to the
use of novel materials for photonics, the employment of optical microcavities in
combination with quantum materials has become very attractive for cavity quantumelectrodynamics studies and nanophotonics, which nowadays go beyond the use of
common semiconductor materials and epitaxially-grown quantum structures. Such
concepts are for instance subject of the research activities jointly performed by the
author with partners from the Zhejiang University, Hangzhou, with eyes towards
efficient quantum emitters for future quantum communication purposes. The principal investigators performed, both, jointly and individually scientific activities to
identify new application potentials of 2D materials, as well as zero-dimensional
structures, and to investigate light–matter interactions as well as a variety of novel
materials in optical cavities. For instance, the author explored concepts to smoothly
tune the coupling regime from weak to strong across the exceptional point. Also, a
new approach was targeted to deliver good enough optical microresonators based on
fibre technologies and high-reflectivity interfaces for efficient in- and out-coupling
of signal from flexible and tunable light–matter-coupled systems, as produced and
studied in the Hangzhou nanophotonics laboratories and further investigated in Marburg. In addition, to bring 2D semiconductors closer to applications and to improve
the emission properties, photoluminescence (PL) enhancement was recently studied
using WS 2 on nano-fabricated optical microresonators, which are achieved from ring
patterns (in-plane Bragg gratings) in a dielectric substrate. This approach pursued
for controlled emission rates and profiles by the author, and jointly published with
co-workers from Frankfurt, Hangzhou, and Marburg, allows combining both vertical
and horizontal interference effects to improve both in-coupling into and out-coupling
of light from 2D materials. Such structures could be at the core of future on-chip
optical interconnects for light-based information processing purposes. Photodetectors, photovoltaics, nonlinear optics and light-emitting diodes involving 2D materials
could strongly benefit from these advances for the concept introduced.
In the context of strong light–matter interactions, polariton physics offers an exciting playground for the study of Bose–Einstein-like condensation phenomena, as well
as the related effects, such as superfluidity. Employing 2D materials in this domain
has further enriched the field due to spin- and valley-sensitivity of TMDCs. The
manipulation and control of hybrid quantum states in matter with external photons is
an interesting direction to continue polariton research, after having studied various
examples of polariton condensates, their generation and their correlations. Studies
by the author on polaritons and excitons in external fields were deepened in the past
years as summarised in this work.
Other international and domestic collaborations have so far enabled effective studies on semiconductor disk lasers, for instance with regard to the self-mode-locking
effect and performance boosts for single-frequency or THz-generating devices, as
well as on material spectroscopy and quantum optics. In one case, a record flux
from a single-photon source was achieved by combining self-built pulsed lasers with
quantum emitters from Berlin, Germany.