102
4 In the Field of Quantum Technologies
in the Glauber state |α).
4 A fundamental and theoretical overview can be obtained
for instance through [5].
Their temporal and spatial coherence properties render coherent light sources
indispensable tools in modern optics and light-based techniques. Numerous excellent
descriptions of laser theory and technology exist in the vast pool of literature (see for
instance [6]), and it is not the aim of this section to deliver a comprehensive summary
of this field. Instead, a bridge to semiconductor lasers shall be offered, which allows
the summary of specific investigations in this domain.
4.2.1 Semiconductor Lasers: From Efficient Nanolasers to
Powerful External–Cavity Lasers
Miniaturisation and diversification of employable gain materials have played important roles in the achievement of compact devices, higher efficiencies and wavelength
versatility. In addition, semiconductor lasers can be well integrated in electronic
devices. In fact, numerous scientists have been awarded with Nobel prices for their
foundational works that enabled new lasers and laser technologies. The class of semiconductor lasers can be further separated into two main types of lasers, which are
known as edge emitters and surface emitters, according to the optical output direction
obtained from the respective device with regard to the semiconductor chip. Among
the vertical emitters, one typically finds laser diodes in the form of VCSELs,
5 and
their siblings with external cavity referred to as VECSELs,
6 which are predominantly optically-pumped semiconductor disk lasers (SDLs). A review on the recent
advances in VECSELs is given in [49], and the interested reader is further referred
to [50–52].
Semiconductor Laser Development
While major aims in the semiconductor laser community can be defined as achieving
ultra-low-threshold or even threshold-less lasers [53–56], or ecologically–friendly
(“green”) diode lasers [57], or the ultimate nanolaser [58], others target ultrashort
pulse generation or high output powers. One key element for very efficient devices are
high-quality microresonators (see [59]). Another key element for optimised light–
matter interactions are low-dimensional quantum structures, which can be incorporated into low-mode-volume optical cavities, such as in the case of quantum-dot
micropillar [60] or quantum-dot microdisk [61] lasers, to name but a few.
In contrast to the ultra-efficiency schemes, ensemble-quantum-dot systems in
VECSELs combined with appropriate thermal management can even show record
high output powers from a single laser chip with optically-pumped quantum-dots
4 The quantum mechanical description of photon correlations and optical coherence was first provided by Glauber [45–47], after which the coherent state was named, and Sudarshan [48].
5 Acronym for vertical-cavity surface-emitting laser.
6 Acronym for vertical-external-cavity surface-emitting laser.
4 In the Field of Quantum Technologies
in the Glauber state |α).
4 A fundamental and theoretical overview can be obtained
for instance through [5].
Their temporal and spatial coherence properties render coherent light sources
indispensable tools in modern optics and light-based techniques. Numerous excellent
descriptions of laser theory and technology exist in the vast pool of literature (see for
instance [6]), and it is not the aim of this section to deliver a comprehensive summary
of this field. Instead, a bridge to semiconductor lasers shall be offered, which allows
the summary of specific investigations in this domain.
4.2.1 Semiconductor Lasers: From Efficient Nanolasers to
Powerful External–Cavity Lasers
Miniaturisation and diversification of employable gain materials have played important roles in the achievement of compact devices, higher efficiencies and wavelength
versatility. In addition, semiconductor lasers can be well integrated in electronic
devices. In fact, numerous scientists have been awarded with Nobel prices for their
foundational works that enabled new lasers and laser technologies. The class of semiconductor lasers can be further separated into two main types of lasers, which are
known as edge emitters and surface emitters, according to the optical output direction
obtained from the respective device with regard to the semiconductor chip. Among
the vertical emitters, one typically finds laser diodes in the form of VCSELs,
5 and
their siblings with external cavity referred to as VECSELs,
6 which are predominantly optically-pumped semiconductor disk lasers (SDLs). A review on the recent
advances in VECSELs is given in [49], and the interested reader is further referred
to [50–52].
Semiconductor Laser Development
While major aims in the semiconductor laser community can be defined as achieving
ultra-low-threshold or even threshold-less lasers [53–56], or ecologically–friendly
(“green”) diode lasers [57], or the ultimate nanolaser [58], others target ultrashort
pulse generation or high output powers. One key element for very efficient devices are
high-quality microresonators (see [59]). Another key element for optimised light–
matter interactions are low-dimensional quantum structures, which can be incorporated into low-mode-volume optical cavities, such as in the case of quantum-dot
micropillar [60] or quantum-dot microdisk [61] lasers, to name but a few.
In contrast to the ultra-efficiency schemes, ensemble-quantum-dot systems in
VECSELs combined with appropriate thermal management can even show record
high output powers from a single laser chip with optically-pumped quantum-dots
4 The quantum mechanical description of photon correlations and optical coherence was first provided by Glauber [45–47], after which the coherent state was named, and Sudarshan [48].
5 Acronym for vertical-cavity surface-emitting laser.
6 Acronym for vertical-external-cavity surface-emitting laser.