Chapter 6
Effects of Quantisation
Abstract Fundamental quantum-physical effects are nowadays harnessed in practical devices through different means. On the one hand, quantum potential boxes can
be employed to alter electronic or photonic properties depending on the application.
From bulk to zero-dimensional structures, the quantisation of energy states for physical entities, such as electrons or photons, gets pronounced and the density of states
is strongly modified based on the dimensionality of the host system. Therefor, the
size of a confinement potential provided by a host structure is typically adjusted to
the length scale corresponding to the respective particle’s spatial extent, resulting in
a quantum structure. Generally, quantum structures can be beneficial for optoelectronic or quantum devices due to several aspects, such as strong spatial confinement,
tailored energy transport or storage, efficient lasing or nonclassical light generation,
and altered interactions of their particles with their environment or other particles. On
the other hand, the control of quantum coupling phenomena or the use of many-body
effects can enable novel devices or open up new pathways to a fundamental exploration of quantum effects, such as hybridisation, superposition, collective phenomena
and cavity quantum electrodynamics. Thus, this chapter aims at an introduction to
prominent effects of size reduction to the nanoscale for electronics or microscale for
photonics, as well as a summary of benefits and applications, giving examples from
optoelectronics and nanophotonics.
6.1 Miniaturisation Towards Quantum Structures
The reduction of a structure’s size brings obvious advantages with it, as for example
miniaturised devices strongly benefit from microscopic building blocks. In addition,
it is well understood that clusters of matter, such as nanoparticles or microparticles,
can act as noticeable scattering centers for propagating (electromagnetic) waves
when the structure size becomes more or less—in terms of the order of magnitude—
comparable to the wavelength. Similarly, apertures or device facets on that length
scale introduce considerable diffraction effects. However, more intriguing in terms
of miniaturisation remains the fact that the device physics gets influenced by the
size of a structure which can have a remarkable impact on various properties when
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
A. Rahimi-Iman, Semiconductor Photonics of Nanomaterials and Quantum Structures,
Springer Series in Solid-State Sciences 196,
https://doi.org/10.1007/978-3-030-69352-7_6
187
Effects of Quantisation
Abstract Fundamental quantum-physical effects are nowadays harnessed in practical devices through different means. On the one hand, quantum potential boxes can
be employed to alter electronic or photonic properties depending on the application.
From bulk to zero-dimensional structures, the quantisation of energy states for physical entities, such as electrons or photons, gets pronounced and the density of states
is strongly modified based on the dimensionality of the host system. Therefor, the
size of a confinement potential provided by a host structure is typically adjusted to
the length scale corresponding to the respective particle’s spatial extent, resulting in
a quantum structure. Generally, quantum structures can be beneficial for optoelectronic or quantum devices due to several aspects, such as strong spatial confinement,
tailored energy transport or storage, efficient lasing or nonclassical light generation,
and altered interactions of their particles with their environment or other particles. On
the other hand, the control of quantum coupling phenomena or the use of many-body
effects can enable novel devices or open up new pathways to a fundamental exploration of quantum effects, such as hybridisation, superposition, collective phenomena
and cavity quantum electrodynamics. Thus, this chapter aims at an introduction to
prominent effects of size reduction to the nanoscale for electronics or microscale for
photonics, as well as a summary of benefits and applications, giving examples from
optoelectronics and nanophotonics.
6.1 Miniaturisation Towards Quantum Structures
The reduction of a structure’s size brings obvious advantages with it, as for example
miniaturised devices strongly benefit from microscopic building blocks. In addition,
it is well understood that clusters of matter, such as nanoparticles or microparticles,
can act as noticeable scattering centers for propagating (electromagnetic) waves
when the structure size becomes more or less—in terms of the order of magnitude—
comparable to the wavelength. Similarly, apertures or device facets on that length
scale introduce considerable diffraction effects. However, more intriguing in terms
of miniaturisation remains the fact that the device physics gets influenced by the
size of a structure which can have a remarkable impact on various properties when
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
A. Rahimi-Iman, Semiconductor Photonics of Nanomaterials and Quantum Structures,
Springer Series in Solid-State Sciences 196,
https://doi.org/10.1007/978-3-030-69352-7_6
187