1 Nanoplasmonics: From Present into Future
77
specific spaser with the chosen set of parameters, this gain is ≈60, which is more
than sufficient for the digital information processing. Thus this spaser can make
a high-gain, ∼10 THz-bandwidth logical amplifier or dynamical memory cell with
excellent prospects of applications.
The last but not the least regime to consider is that of the pulse pumping in the
bistable spaser. In this case, the population inversion (n 21 = 0.65) is created by a
short pulse at t = 0 and simultaneously initial SP population N n is created. Both are
simulated as the initial conditions in Eqs. (1.67)–(1.70). The corresponding results
are displayed in Figs. 1.30g, h.
When the initial SP population exceeds the critical one of N n = 1 (the blue,
green, and red curves), the spaser responds with generating a short (duration less
than 100 fs) pulse of the SP population (and the corresponding local fields) within
a time 100 fs (panel g). Simultaneously, the inversion is rapidly (within ∼100 fs)
exhausted (panel h).
In contrast, when the initial SP population N n is less than the critical one (i.e., N n <
1 in this specific case), the spaser rapidly (within a time 100 fs) relaxes as N n → 0
through a series of realaxation oscillations—see the black and magenta curves in
Fig. 1.30g. The corresponding inversion decays in this case almost exponentially
with a characteristic time ∼1 ps determined by the enhanced energy transfer to the
SP mode in the metal—see the corresponding curves in panel (h). Note that the SP
population decays faster when the spaser is above the generation threshold due to the
stimulated SP emission leading to the higher local fields and enhanced relaxation.
1.5.7 Compensation of Loss by Gain and Spasing
1.5.7.1 Introduction to Loss Compensation by Gain
A problem for many applications of plasmonics and metamaterials is posed by losses
inherent in the interaction of light with metals. There are several ways to bypass,
mitigate, or overcome the detrimental effects of these losses, which we briefly discuss
below.
(i) The most common approach consists in employing effects where the losses are
not fundamentally important such as surface plasmon polariton (SPP) propagation used in sensing [23], ultramicroscopy [16, 19], and solar energy conversion [26]. For realistic losses, there are other effects and applications that
are not prohibitively suppressed by the losses and useful, in particular, sensing
based on SP resonances and surface enhanced Raman scattering (SERS) [23,
178, 242, 289, 290].
(ii) Another promising idea is to use superconducting plasmonics to dramatically
reduce losses [74, 291–293]. However, this is only applicable for frequencies
below the superconducting gaps, i.e., in the terahertz region.
77
specific spaser with the chosen set of parameters, this gain is ≈60, which is more
than sufficient for the digital information processing. Thus this spaser can make
a high-gain, ∼10 THz-bandwidth logical amplifier or dynamical memory cell with
excellent prospects of applications.
The last but not the least regime to consider is that of the pulse pumping in the
bistable spaser. In this case, the population inversion (n 21 = 0.65) is created by a
short pulse at t = 0 and simultaneously initial SP population N n is created. Both are
simulated as the initial conditions in Eqs. (1.67)–(1.70). The corresponding results
are displayed in Figs. 1.30g, h.
When the initial SP population exceeds the critical one of N n = 1 (the blue,
green, and red curves), the spaser responds with generating a short (duration less
than 100 fs) pulse of the SP population (and the corresponding local fields) within
a time 100 fs (panel g). Simultaneously, the inversion is rapidly (within ∼100 fs)
exhausted (panel h).
In contrast, when the initial SP population N n is less than the critical one (i.e., N n <
1 in this specific case), the spaser rapidly (within a time 100 fs) relaxes as N n → 0
through a series of realaxation oscillations—see the black and magenta curves in
Fig. 1.30g. The corresponding inversion decays in this case almost exponentially
with a characteristic time ∼1 ps determined by the enhanced energy transfer to the
SP mode in the metal—see the corresponding curves in panel (h). Note that the SP
population decays faster when the spaser is above the generation threshold due to the
stimulated SP emission leading to the higher local fields and enhanced relaxation.
1.5.7 Compensation of Loss by Gain and Spasing
1.5.7.1 Introduction to Loss Compensation by Gain
A problem for many applications of plasmonics and metamaterials is posed by losses
inherent in the interaction of light with metals. There are several ways to bypass,
mitigate, or overcome the detrimental effects of these losses, which we briefly discuss
below.
(i) The most common approach consists in employing effects where the losses are
not fundamentally important such as surface plasmon polariton (SPP) propagation used in sensing [23], ultramicroscopy [16, 19], and solar energy conversion [26]. For realistic losses, there are other effects and applications that
are not prohibitively suppressed by the losses and useful, in particular, sensing
based on SP resonances and surface enhanced Raman scattering (SERS) [23,
178, 242, 289, 290].
(ii) Another promising idea is to use superconducting plasmonics to dramatically
reduce losses [74, 291–293]. However, this is only applicable for frequencies
below the superconducting gaps, i.e., in the terahertz region.