108
4 In the Field of Quantum Technologies
by the author’s team to analyse plastics, to detect microplastics or to specify debris in
tissue samples led to exciting insights into the possibilities involving LIPS, although
preliminary works have not reached an advanced stage to exploit this method systematically. Nevertheless, plasma parameters were studied for molybdenum samples
to improve the measurement capabilities collaboratively with partners [115]. The
molybdenum-I lines were corrected against self-absorption and the corrected values
of the temperature and the electron density were obtained.
4.2.2 Novel Coherent Light Sources
The field of semiconductor laser research is so vast, that these mentioned achievements in fact appear like a small drop in a large ocean. The selection of examples and
achievements is strongly related to the work of the author, and works by a plethora
of other research groups and institutions worldwide would be hardly adequately
reflected in this section if the goal was to provide a topical overview.
Lasers can be widely used in numerous domains, such as for industrial manufacturing, health care, scientific diagnostics and fabrication tools, information processing,
security applications and many more, and no attempt has been made to summarise
them accurately in this section. Instead, here, another aspect of coherent light source
engineering shall be briefly highlighted, that is the development of a platform not
based on stimulated emission of light but stimulated scattering of bosonic polaritons
into a macroscopically-occupied final state (an overview of the polariton condensation subject is for instance provided in [116]).
Polariton Laser as Energy-Efficient Coherent Light Source
Towards novel sources of coherent light, the polariton laser had been proposed [122,
123] and realised in multiple forms, both optically [124–134] and electrically pumped
[117, 118, 135, 136] (cf. Fig.4.4). Recently, even coherent polariton lasers were
demonstrated based on adjusted ground-state–reservoir interactions (e.g. in singlemode devices) [133], as promoted by the discrete emission modes in micropillars
[137]. The prospects of coherent polariton devices and their applications are for
instance further discussed in [138, 139]. More about the topic of polariton lasers,
the difference to conventional lasers and the identification of lasing in the strongcoupling regime is summarised in [120].
Spinor Polariton Condensates
To understand their properties better, studies on optically pumped polariton condensates (such as in [144–146]) in magnetic fields were performed [142, 143] in
continuation of previous works [118, 145, 147, 202]. This was pursued for instance
to shed light on the suppression of a Zeeman splitting at a critical magnetic field due
to the spin analogue of the Meissner effect—the “spin Meissner effect” [140] (cf.
Fig. 4.5)—for spinor condensates. Moreover, this was also pursued to analyse their
polarisation-resolved second-order coherence (g
(2)
σ ± (0)) as a function of the excitation
density and magnetic flux. In fact, polaritons in external fields offer many possibilities
to manipulate and control the hybrid quasi-particles formed in optical microcavities
(see for instance [148]).
4 In the Field of Quantum Technologies
by the author’s team to analyse plastics, to detect microplastics or to specify debris in
tissue samples led to exciting insights into the possibilities involving LIPS, although
preliminary works have not reached an advanced stage to exploit this method systematically. Nevertheless, plasma parameters were studied for molybdenum samples
to improve the measurement capabilities collaboratively with partners [115]. The
molybdenum-I lines were corrected against self-absorption and the corrected values
of the temperature and the electron density were obtained.
4.2.2 Novel Coherent Light Sources
The field of semiconductor laser research is so vast, that these mentioned achievements in fact appear like a small drop in a large ocean. The selection of examples and
achievements is strongly related to the work of the author, and works by a plethora
of other research groups and institutions worldwide would be hardly adequately
reflected in this section if the goal was to provide a topical overview.
Lasers can be widely used in numerous domains, such as for industrial manufacturing, health care, scientific diagnostics and fabrication tools, information processing,
security applications and many more, and no attempt has been made to summarise
them accurately in this section. Instead, here, another aspect of coherent light source
engineering shall be briefly highlighted, that is the development of a platform not
based on stimulated emission of light but stimulated scattering of bosonic polaritons
into a macroscopically-occupied final state (an overview of the polariton condensation subject is for instance provided in [116]).
Polariton Laser as Energy-Efficient Coherent Light Source
Towards novel sources of coherent light, the polariton laser had been proposed [122,
123] and realised in multiple forms, both optically [124–134] and electrically pumped
[117, 118, 135, 136] (cf. Fig.4.4). Recently, even coherent polariton lasers were
demonstrated based on adjusted ground-state–reservoir interactions (e.g. in singlemode devices) [133], as promoted by the discrete emission modes in micropillars
[137]. The prospects of coherent polariton devices and their applications are for
instance further discussed in [138, 139]. More about the topic of polariton lasers,
the difference to conventional lasers and the identification of lasing in the strongcoupling regime is summarised in [120].
Spinor Polariton Condensates
To understand their properties better, studies on optically pumped polariton condensates (such as in [144–146]) in magnetic fields were performed [142, 143] in
continuation of previous works [118, 145, 147, 202]. This was pursued for instance
to shed light on the suppression of a Zeeman splitting at a critical magnetic field due
to the spin analogue of the Meissner effect—the “spin Meissner effect” [140] (cf.
Fig. 4.5)—for spinor condensates. Moreover, this was also pursued to analyse their
polarisation-resolved second-order coherence (g
(2)
σ ± (0)) as a function of the excitation
density and magnetic flux. In fact, polaritons in external fields offer many possibilities
to manipulate and control the hybrid quasi-particles formed in optical microcavities
(see for instance [148]).