250
T. C. Jagadale and S.-W. Chu
Figure 10.3c shows that as the excitation wavelength is closer to plasmonic resonance peak, the required intensity for saturation is smaller, suggesting that the
saturable scattering is dominated by surface plasmon resonance of GNS.
10.3.2 Nonlinear Scattering in Various Plasmonic Structures
In addition to gold nanospheres, we found that the nonlinear scattering is ubiquitous
in various plasmonics materials and structures [23]. Here we give some examples
of gold nanorods (GNR), silver nanosphere (SNS), and gold bowtie antenna. These
studies not only help to extend the applicable wavelength ranges but also clarifies
the mechanism of nonlinear scattering.
The GNR used in our study has 60 nm length and 10 nm width, resulting in a strong
resonance peak at ~800 nm that are preferred for deep-tissue imaging applications.
By using a 785 nm excitation, which is close to the peak, Fig. 10.4a shows a clear
nonlinear behaviour in GNRs. The threshold of saturation in scattering locates at
about 3 × 10
5 W/cm
2 , while the onset of reverse saturation in scattering occurs at 7 ×
10
5 W/cm
2 . Inset in Fig. 10.4a shows that scattering signal is linearly proportional
to the excitation at lower excitation intensities. Figure 10.4b presents the PSF of
a single GNR at excitation intensity that is adequate to induce saturation, but not
reverse saturation, manifesting that nonlinear effect starts at the centre of focus under
Fig. 10.4 a Scattering intensity at different 785 nm excitation intensities of a GNR; b PSF profile at
5.2 × 10 5 W/cm 2 demonstrating saturation in a single GNR; c scattering intensity of a single 80 nm
SNS at different 473 nm excitation intensities; d PSF profiles at 7.8 × 10 5 W/cm 2 demonstrating
saturation in a single SNS; e statistical threshold intensities for nonlinear scattering of SNS with
different excitation wavelengths; f demonstration of nonlinear scattering in gold nanoantenna.
Reproduced from [23] with permission from American Chemical Society
T. C. Jagadale and S.-W. Chu
Figure 10.3c shows that as the excitation wavelength is closer to plasmonic resonance peak, the required intensity for saturation is smaller, suggesting that the
saturable scattering is dominated by surface plasmon resonance of GNS.
10.3.2 Nonlinear Scattering in Various Plasmonic Structures
In addition to gold nanospheres, we found that the nonlinear scattering is ubiquitous
in various plasmonics materials and structures [23]. Here we give some examples
of gold nanorods (GNR), silver nanosphere (SNS), and gold bowtie antenna. These
studies not only help to extend the applicable wavelength ranges but also clarifies
the mechanism of nonlinear scattering.
The GNR used in our study has 60 nm length and 10 nm width, resulting in a strong
resonance peak at ~800 nm that are preferred for deep-tissue imaging applications.
By using a 785 nm excitation, which is close to the peak, Fig. 10.4a shows a clear
nonlinear behaviour in GNRs. The threshold of saturation in scattering locates at
about 3 × 10
5 W/cm
2 , while the onset of reverse saturation in scattering occurs at 7 ×
10
5 W/cm
2 . Inset in Fig. 10.4a shows that scattering signal is linearly proportional
to the excitation at lower excitation intensities. Figure 10.4b presents the PSF of
a single GNR at excitation intensity that is adequate to induce saturation, but not
reverse saturation, manifesting that nonlinear effect starts at the centre of focus under
Fig. 10.4 a Scattering intensity at different 785 nm excitation intensities of a GNR; b PSF profile at
5.2 × 10 5 W/cm 2 demonstrating saturation in a single GNR; c scattering intensity of a single 80 nm
SNS at different 473 nm excitation intensities; d PSF profiles at 7.8 × 10 5 W/cm 2 demonstrating
saturation in a single SNS; e statistical threshold intensities for nonlinear scattering of SNS with
different excitation wavelengths; f demonstration of nonlinear scattering in gold nanoantenna.
Reproduced from [23] with permission from American Chemical Society