5 Light–Nanomatter Chiral Interaction in Optical-Force Effects
123
edges of metallic structures, as the longitudinal localized component is dominant
there. However, optical force is significantly sensitive to the spatial distribution of
the field, which includes both the transverse traveling component and longitudinal
localized one. This sensitivity feature can be utilized to observe the 3D field distribution by using a microscope. Our numerical simulations showed that the optical-force
microscope satisfactorily visualized the 3D NF-CD.
The second topic is the rotational-motion control of NPs in the nanoscale area,
and this control is realized using the chiral interaction between the circularly polarized light and metallic nanocomplex. We theoretically demonstrated that the conversion between the spin angular momentum and orbital angular momentum using
the aforementioned interaction induced the rotational motion of NPs. Furthermore, it
was shown that by performing the balance control between the dissipation force and
gradient force via nonlinear optical responses, we could switch the rotation direction
of NPs.
The studies introduced in this chapter confirmed the essential roles of optical-force
effects to research the chiral interactions at the metallic nanostructures that sustain
LSP. It is important for various kinds of technologies to analyze molecular substances
and control the mechanical motion of nanostructures via chiral interactions. The
present results might stimulate further study of microscopic chiral interactions in
various research domains.
Acknowledgements The authors thank Y. Togawa, S. Hashiyada, H. Okamoto and K. Sasaki for
their fruitful discussions. This work was supported in part by JSPS KAKENHI Grant Number
JP16H06504 for Scientific Research on Innovative Areas “Nano-Material Optical-Manipulation”.
Appendix 1
Balance Between Dissipative Force and Gradient Force Under a Strong Near
Field [25]
To understand the balance between the dissipative force and gradient force exerted
on an NP under a strong near field, we considered the time-averaged optical force as
follows:
F(ω) =
1
2
Re
V
dr[∇E(r, ω)
∗
] · P NP (r, ω)
.
(5.12)
Here, we consider an evanescent field with a simple profile as follows:
E(r, ω) = E(x, y)e
i(k 1 +ik 2 )z
,
(5.13)
where k 1 and k 2 denote the wavenumber and extinction coefficients along the zdirection, respectively. The induced polarization is represented using complex susceptibility as follows:
123
edges of metallic structures, as the longitudinal localized component is dominant
there. However, optical force is significantly sensitive to the spatial distribution of
the field, which includes both the transverse traveling component and longitudinal
localized one. This sensitivity feature can be utilized to observe the 3D field distribution by using a microscope. Our numerical simulations showed that the optical-force
microscope satisfactorily visualized the 3D NF-CD.
The second topic is the rotational-motion control of NPs in the nanoscale area,
and this control is realized using the chiral interaction between the circularly polarized light and metallic nanocomplex. We theoretically demonstrated that the conversion between the spin angular momentum and orbital angular momentum using
the aforementioned interaction induced the rotational motion of NPs. Furthermore, it
was shown that by performing the balance control between the dissipation force and
gradient force via nonlinear optical responses, we could switch the rotation direction
of NPs.
The studies introduced in this chapter confirmed the essential roles of optical-force
effects to research the chiral interactions at the metallic nanostructures that sustain
LSP. It is important for various kinds of technologies to analyze molecular substances
and control the mechanical motion of nanostructures via chiral interactions. The
present results might stimulate further study of microscopic chiral interactions in
various research domains.
Acknowledgements The authors thank Y. Togawa, S. Hashiyada, H. Okamoto and K. Sasaki for
their fruitful discussions. This work was supported in part by JSPS KAKENHI Grant Number
JP16H06504 for Scientific Research on Innovative Areas “Nano-Material Optical-Manipulation”.
Appendix 1
Balance Between Dissipative Force and Gradient Force Under a Strong Near
Field [25]
To understand the balance between the dissipative force and gradient force exerted
on an NP under a strong near field, we considered the time-averaged optical force as
follows:
F(ω) =
1
2
Re
V
dr[∇E(r, ω)
∗
] · P NP (r, ω)
.
(5.12)
Here, we consider an evanescent field with a simple profile as follows:
E(r, ω) = E(x, y)e
i(k 1 +ik 2 )z
,
(5.13)
where k 1 and k 2 denote the wavenumber and extinction coefficients along the zdirection, respectively. The induced polarization is represented using complex susceptibility as follows: