244
8 Conclusion and Outlook
technique by the group of P. J. Klar in Giessen promises benefits to such developments [126–129]. Using metallic or other-type nanoparticles, and depositing them
on the surface of the 2D material, may allow one to tune the optical response of 2D
materials, with eyes towards improving the optoelectronic properties of 2D devices
such as detectors or solar cells.
2D-Materials Synthesis and Stacking
The development as well as improvement of 2D materials syntheses remains a key
goal of FNMS-COOP project partners working together with J. He at the National
Center for Nanoscience and Technology (short: Nanocenter) in Beijing. The demonstration of high-quality large-area synthesised monolayer and multilayer crystals and
their comparison with their mechanically exfoliated counterparts will improve the
capabilities in terms of nanodevice fabrication. Direct synthesis of vdW heterostructures remains one goal on that path. Also, the development of improved electrical
contacting schemes is currently under investigation. Future endeavours will address
van-der-Waals epitaxy, which is necessary for more complex vertical and horizontal
alignment of different 2D materials, and which requires joint characterisation efforts.
Such research is beneficial to activities in both host countries of the cooperation group
regarding 2D devices.
High-Quality Tunable Open Optical Microcavities
For practical photonic devices, concepts of optics and materials sciences need to be
combined. This typically leads to fascinating light–matter interaction studies, where
quantum emitters are placed inside optical microcavities or waveguide structures.
Microcavities confine the light field in a small mode volume (with high free spectral
range (FSR)) and bring cavity photons into coupling with excitons in the respective
quantum material by tuning individual modes into resonance with each other. Indeed,
if the resonator quality (Q-factor) and the FSR are too small, the cavity mode is not
sharp enough (and, thus, photon lifetimes not long enough) and the optical resonances are not separated enough, respectively, to enable the clear observation of the
desired light–matter coupling effects. Recently, collaborative work has demonstrated
a new approach to produce optical microresonators based on fibre technologies for
nanophotonics [112], offering the team different variations of open tunable microcavities with Q-factors between few hundreds up to few thousands. As part of ongoing
project activities, high-quality 2D materials and different colloidal quantum dots are
going to be employed inside these fibre-based microcavities and optical properties
of such structures systematically investigated by the author and co-workers (group
of W. Fang in Hangzhou) jointly with eyes towards weak and strong coupling, and
single-photon generation.
Strong Light–Matter Coupling with 2D Materials
Quasi-particle formation in light–matter-coupled microresonators gives access to the
intriguing physics of Bose–Einstein condensates at elevated temperatures up to room
temperature, provided that the underlying matter excitations for the so-called cavity–
polaritons, the excitons, prevail at the respective temperature and at the needed particle densities for stimulated scattering effects [45, 48]. 2D materials have promised a
8 Conclusion and Outlook
technique by the group of P. J. Klar in Giessen promises benefits to such developments [126–129]. Using metallic or other-type nanoparticles, and depositing them
on the surface of the 2D material, may allow one to tune the optical response of 2D
materials, with eyes towards improving the optoelectronic properties of 2D devices
such as detectors or solar cells.
2D-Materials Synthesis and Stacking
The development as well as improvement of 2D materials syntheses remains a key
goal of FNMS-COOP project partners working together with J. He at the National
Center for Nanoscience and Technology (short: Nanocenter) in Beijing. The demonstration of high-quality large-area synthesised monolayer and multilayer crystals and
their comparison with their mechanically exfoliated counterparts will improve the
capabilities in terms of nanodevice fabrication. Direct synthesis of vdW heterostructures remains one goal on that path. Also, the development of improved electrical
contacting schemes is currently under investigation. Future endeavours will address
van-der-Waals epitaxy, which is necessary for more complex vertical and horizontal
alignment of different 2D materials, and which requires joint characterisation efforts.
Such research is beneficial to activities in both host countries of the cooperation group
regarding 2D devices.
High-Quality Tunable Open Optical Microcavities
For practical photonic devices, concepts of optics and materials sciences need to be
combined. This typically leads to fascinating light–matter interaction studies, where
quantum emitters are placed inside optical microcavities or waveguide structures.
Microcavities confine the light field in a small mode volume (with high free spectral
range (FSR)) and bring cavity photons into coupling with excitons in the respective
quantum material by tuning individual modes into resonance with each other. Indeed,
if the resonator quality (Q-factor) and the FSR are too small, the cavity mode is not
sharp enough (and, thus, photon lifetimes not long enough) and the optical resonances are not separated enough, respectively, to enable the clear observation of the
desired light–matter coupling effects. Recently, collaborative work has demonstrated
a new approach to produce optical microresonators based on fibre technologies for
nanophotonics [112], offering the team different variations of open tunable microcavities with Q-factors between few hundreds up to few thousands. As part of ongoing
project activities, high-quality 2D materials and different colloidal quantum dots are
going to be employed inside these fibre-based microcavities and optical properties
of such structures systematically investigated by the author and co-workers (group
of W. Fang in Hangzhou) jointly with eyes towards weak and strong coupling, and
single-photon generation.
Strong Light–Matter Coupling with 2D Materials
Quasi-particle formation in light–matter-coupled microresonators gives access to the
intriguing physics of Bose–Einstein condensates at elevated temperatures up to room
temperature, provided that the underlying matter excitations for the so-called cavity–
polaritons, the excitons, prevail at the respective temperature and at the needed particle densities for stimulated scattering effects [45, 48]. 2D materials have promised a