1 Nanoplasmonics: From Present into Future
55
The work of Ref. [212] has fully implemented the idea of Ref. [210] on the spatialphase-modulation control of the SPP wavefronts to position a SPP nanofocus at a
desired location at the surface. However, it employs only CW excitation and does
not exploit a potential femtosecond temporal degree of freedom to achieve such a
nanofocusing at a predetermined moment of time as in Ref. [210].
1.5 Quantum Nanoplasmonics: Spaser and Nanoplasmonics
with Gain
1.5.1 Introduction to Spasers and Spasing
Not just a promise anymore [241], nanoplasmonics has delivered a number of important applications: ultrasensing [242], scanning near-field optical microscopy [190,
243], SP-enhanced photodetectors [53], thermally assisted magnetic recording [244],
generation of extreme uv [138], biomedical tests [242, 245], SP-assisted thermal cancer treatment [246], plasmonic enhanced generation of extreme ultraviolet (EUV)
pulses [138] and extreme ultraviolet to soft x-ray (XUV) pulses [247], and many
others—see also Ref. [23].
To continue its vigorous development, nanoplasmonics needs an active device—
near-field generator and amplifier of nanolocalized optical fields, which has until
recently been absent. A nanoscale amplifier in microelectronics is the metal-oxidesemiconductor field effect transistor (MOSFET) [248, 249], which has enabled
all contemporary digital electronics, including computers and communications and
enabled the present day technology as we know it. However, the MOSFET is limited by frequency and bandwidth to 100 GHz, which is already a limiting factor
in further technological development. Another limitation of the MOSFET is its high
sensitivity to temperature, electric fields, and ionizing radiation, which limits its use
in extreme environmental conditions and nuclear technology and warfare.
An active element of nanoplasmonics is the spaser (Surface Plasmon Amplification by Stimulated Emission of Radiation), which was proposed [31, 250] as a
nanoscale quantum generator of nanolocalized coherent and intense optical fields.
The idea of spaser has been further developed theoretically [139–141, 251]. Spaser
effect has recently been observed experimentally [252]. Also a number of SPP spasers
(also called nanolasers) have been experimentally observed [253–256].
Spaser is a nanoplasmonic counterpart of laser: it is a quantum generator and
nanoamplifier where photons as the generated quanta are replaced by SPs. Spaser
consists of a metal nanoparticle, which plays a role of the laser cavity (resonator),
and the gain medium. Figure 1.25 schematically illustrates geometry of a spaser
introduced in the original article [31], which contains a V-shaped metal nanoparticle
surrounded by a layer of semiconductor nanocrystal quantum dots.
55
The work of Ref. [212] has fully implemented the idea of Ref. [210] on the spatialphase-modulation control of the SPP wavefronts to position a SPP nanofocus at a
desired location at the surface. However, it employs only CW excitation and does
not exploit a potential femtosecond temporal degree of freedom to achieve such a
nanofocusing at a predetermined moment of time as in Ref. [210].
1.5 Quantum Nanoplasmonics: Spaser and Nanoplasmonics
with Gain
1.5.1 Introduction to Spasers and Spasing
Not just a promise anymore [241], nanoplasmonics has delivered a number of important applications: ultrasensing [242], scanning near-field optical microscopy [190,
243], SP-enhanced photodetectors [53], thermally assisted magnetic recording [244],
generation of extreme uv [138], biomedical tests [242, 245], SP-assisted thermal cancer treatment [246], plasmonic enhanced generation of extreme ultraviolet (EUV)
pulses [138] and extreme ultraviolet to soft x-ray (XUV) pulses [247], and many
others—see also Ref. [23].
To continue its vigorous development, nanoplasmonics needs an active device—
near-field generator and amplifier of nanolocalized optical fields, which has until
recently been absent. A nanoscale amplifier in microelectronics is the metal-oxidesemiconductor field effect transistor (MOSFET) [248, 249], which has enabled
all contemporary digital electronics, including computers and communications and
enabled the present day technology as we know it. However, the MOSFET is limited by frequency and bandwidth to 100 GHz, which is already a limiting factor
in further technological development. Another limitation of the MOSFET is its high
sensitivity to temperature, electric fields, and ionizing radiation, which limits its use
in extreme environmental conditions and nuclear technology and warfare.
An active element of nanoplasmonics is the spaser (Surface Plasmon Amplification by Stimulated Emission of Radiation), which was proposed [31, 250] as a
nanoscale quantum generator of nanolocalized coherent and intense optical fields.
The idea of spaser has been further developed theoretically [139–141, 251]. Spaser
effect has recently been observed experimentally [252]. Also a number of SPP spasers
(also called nanolasers) have been experimentally observed [253–256].
Spaser is a nanoplasmonic counterpart of laser: it is a quantum generator and
nanoamplifier where photons as the generated quanta are replaced by SPs. Spaser
consists of a metal nanoparticle, which plays a role of the laser cavity (resonator),
and the gain medium. Figure 1.25 schematically illustrates geometry of a spaser
introduced in the original article [31], which contains a V-shaped metal nanoparticle
surrounded by a layer of semiconductor nanocrystal quantum dots.