60
M. I. Stockman
pumped PbS semiconductor quantum dots [260]. There have also been experimental
investigations reporting the stimulated emission effects of SPs in plasmonic metal
nanoparticles surrounded by gain media with dye molecules [275, 276].
The full loss compensation and amplification of the long-range SPPs at λ =
882 nm in a gold nanostrip waveguide with a dyes solution as a gain medium has
been observed [277]. Another example of full loss compensation has recently been
obtained for thin (∼20 nm thickness) gold stripes (width ∼1 µm) surrounded by a
gain medium containing donor–acceptor with a Fögrster energy transfer to increase
the Stokes shift and decrease absorption at the probe frequency.
At the present time, there have been a number of the successful experimental
observations of the spaser and SPP spasers (the so-called nanolasers). An electricallypumped nanolaser with semiconductor gain medium have been demonstrated [253]
where the lasing modes are SPPs with a one-dimensional confinement to a ∼50 nm
size. Other electrically-pumped nanolasers (SPP spasers) have recently been fabricated and their lasing observed based on a diode with an intrinsic InGaAs gain
media and silver nanocavities as plasmonic cores [278–280]. The latest of these
nanolasers [280] operates at a room temperature and has a relatively small cavity
volume V c ≈ 0.67λ 3 , where vacuum wavelength λ = 1591 nm. This volume is
still much larger than the modal volumes of the spasers with tighter confinement,
especially SP-mode spasers—see below.
A nanolaser with an optically-pumped semiconductor gain medium and a hybrid
semiconductor/metal (CdS/Ag) SPP waveguide has been demonstrated with an
extremely tight transverse (two-dimensional) mode confinement to ∼10 nm size
[254]. This has been followed by the development of CdS/Ag nanolasers generating a visible single mode at a room temperature with a tight one-dimensional
confinement (∼20 nm) and a two-dimensional confinement in the plane of the structure to an area ∼1 µm 2 [255]. A highly efficient SPP spaser in the communication
range (λ = 1.46 µm) with an optical pumping based on a gold film and an InGaAs
semiconductor quantum-well gain medium has recently been reported [256].
Another class of spasers observed are random spasers comprised of a rough metal
nanofilm as a plasmonic component and a dye-doped polymeric film as a gain medium
[281]. The spasing in such systems competes with loss compensation for SPPs propagating at the interface—see also Sect. 1.5.7.
Historically, the first spaser observed was a nanoparticle spaser [252]. This spaser
is a chemically synthesized gold nanosphere of radius 7 nm surrounded by a dielectric shell of a 21 nm outer radius containing immobilized dye molecules. Under
nanosecond optical pumping in the absorption band of the dye, this spaser develops
a relatively narrow-spectrum and intense visible emission that exhibits a pronounced
threshold in pumping intensity. The observed characteristics of this spaser are in
an excellent qualitative agreement and can be fully understood on the basis of the
corresponding theoretical results described below in Sect. 1.5.5.
M. I. Stockman
pumped PbS semiconductor quantum dots [260]. There have also been experimental
investigations reporting the stimulated emission effects of SPs in plasmonic metal
nanoparticles surrounded by gain media with dye molecules [275, 276].
The full loss compensation and amplification of the long-range SPPs at λ =
882 nm in a gold nanostrip waveguide with a dyes solution as a gain medium has
been observed [277]. Another example of full loss compensation has recently been
obtained for thin (∼20 nm thickness) gold stripes (width ∼1 µm) surrounded by a
gain medium containing donor–acceptor with a Fögrster energy transfer to increase
the Stokes shift and decrease absorption at the probe frequency.
At the present time, there have been a number of the successful experimental
observations of the spaser and SPP spasers (the so-called nanolasers). An electricallypumped nanolaser with semiconductor gain medium have been demonstrated [253]
where the lasing modes are SPPs with a one-dimensional confinement to a ∼50 nm
size. Other electrically-pumped nanolasers (SPP spasers) have recently been fabricated and their lasing observed based on a diode with an intrinsic InGaAs gain
media and silver nanocavities as plasmonic cores [278–280]. The latest of these
nanolasers [280] operates at a room temperature and has a relatively small cavity
volume V c ≈ 0.67λ 3 , where vacuum wavelength λ = 1591 nm. This volume is
still much larger than the modal volumes of the spasers with tighter confinement,
especially SP-mode spasers—see below.
A nanolaser with an optically-pumped semiconductor gain medium and a hybrid
semiconductor/metal (CdS/Ag) SPP waveguide has been demonstrated with an
extremely tight transverse (two-dimensional) mode confinement to ∼10 nm size
[254]. This has been followed by the development of CdS/Ag nanolasers generating a visible single mode at a room temperature with a tight one-dimensional
confinement (∼20 nm) and a two-dimensional confinement in the plane of the structure to an area ∼1 µm 2 [255]. A highly efficient SPP spaser in the communication
range (λ = 1.46 µm) with an optical pumping based on a gold film and an InGaAs
semiconductor quantum-well gain medium has recently been reported [256].
Another class of spasers observed are random spasers comprised of a rough metal
nanofilm as a plasmonic component and a dye-doped polymeric film as a gain medium
[281]. The spasing in such systems competes with loss compensation for SPPs propagating at the interface—see also Sect. 1.5.7.
Historically, the first spaser observed was a nanoparticle spaser [252]. This spaser
is a chemically synthesized gold nanosphere of radius 7 nm surrounded by a dielectric shell of a 21 nm outer radius containing immobilized dye molecules. Under
nanosecond optical pumping in the absorption band of the dye, this spaser develops
a relatively narrow-spectrum and intense visible emission that exhibits a pronounced
threshold in pumping intensity. The observed characteristics of this spaser are in
an excellent qualitative agreement and can be fully understood on the basis of the
corresponding theoretical results described below in Sect. 1.5.5.