456
S. Perrin et al.
λ
λ
λ
λ
λ
λ
Fig. 17.9 Evolution of the axial position of the photonic jet intensity peak as a function of the
refractive index of the microsphere for different radii in air. The distance and the radii are expressed
in wavelengths λ. Five radius-dependent curves are represented, going from 1 λ to 9 λ, with an
increment of 2 λ. The black dots represent the position of the photonic jet on the interface of the
microsphere. An imaging system having a refractive index contrast higher than around 1.8 will
always provide a real image [101]
n = 1.5
Virtual imaging
Real imaging
1.0
0.5
0.0
n = 1.9
Photonic jet
Super-resolved image
1.0
0.5
0.0
(a.i)
(a.ii)
(b.i)
(b.ii)
Fig. 17.10 Image formation depending on the refractive index contrast between the microsphere
and the surrounding medium. The microbead is in contact with the object. (a.i) A soda–lime–glass
microsphere (n = 1.52) generates a photonic jet outside the microsphere in air. (a.ii) A virtual
image occurs. (b.i) Using a barium–titanate–glass microsphere (n = 1.90) in air, the focus spot
appears inside the microsphere. (b.ii) The image is real. In both cases, the super-resolved images
were experimentally measured using a 600-nm-period grating placed against the 32 µm-diameter
microspheres [101]. White scale bars represent 2 µm
S. Perrin et al.
λ
λ
λ
λ
λ
λ
Fig. 17.9 Evolution of the axial position of the photonic jet intensity peak as a function of the
refractive index of the microsphere for different radii in air. The distance and the radii are expressed
in wavelengths λ. Five radius-dependent curves are represented, going from 1 λ to 9 λ, with an
increment of 2 λ. The black dots represent the position of the photonic jet on the interface of the
microsphere. An imaging system having a refractive index contrast higher than around 1.8 will
always provide a real image [101]
n = 1.5
Virtual imaging
Real imaging
1.0
0.5
0.0
n = 1.9
Photonic jet
Super-resolved image
1.0
0.5
0.0
(a.i)
(a.ii)
(b.i)
(b.ii)
Fig. 17.10 Image formation depending on the refractive index contrast between the microsphere
and the surrounding medium. The microbead is in contact with the object. (a.i) A soda–lime–glass
microsphere (n = 1.52) generates a photonic jet outside the microsphere in air. (a.ii) A virtual
image occurs. (b.i) Using a barium–titanate–glass microsphere (n = 1.90) in air, the focus spot
appears inside the microsphere. (b.ii) The image is real. In both cases, the super-resolved images
were experimentally measured using a 600-nm-period grating placed against the 32 µm-diameter
microspheres [101]. White scale bars represent 2 µm