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H. Pinhas et al.
two nanostructures since there the described doughnut-like shaping of the PSF will
not occur similar to the Gaussian PSF. Thus, the gap between the two nanostructures
should be smaller than the size of the PSF. Another issue is how the biosample is
placed on top of the nanostructure. To make sure that the probe’s beam will penetrate
into the samples and reach the nanostructure, its chosen wavelength should be long
enough (e.g. near IR) to have sufficient penetration depth.
9.6 Silicon Wafers Imaging
As in the silicon nanostructures concepts described in the earlier sections, the same
approach can be applied on silicon wafers for failure analysis application [32]. As
explained before, an IR laser beam in silicon can be shaped by changing the silicon
complex refractive index locally via another laser beam absorbed in the silicon which
acts as a pump. This change is induced by the change in the free charge carriers (FCC)
density in the silicon due to the absorbed pump beam.
As mentioned earlier, spatial frequencies higher than the ordinary diffractionlimited Gaussian shape PSF frequencies are induced. Moreover, it is important to
note that the proposed mechanism is nonlinear because the absorption coefficient for
the probe is proportional to the power of the pump; therefore the total absorption
of the probe is exponentially related to the absorption coefficient according to the
Beer–Lambert law. Thus, the intensity of the probe is exponentially dependent on
the intensity of the pump. The result of this technique is the improvement in the PSF
of the IR beam.
Here we propose to perform the shaping of the IR beam’s PSF in two modes: First
is to induce a hole at its center. This is generated by applying a narrower Gaussian
pump beam at its center [32], as seen in Fig. 9.12a. For this mode the PSF has a
shape requiring post-processing (decoding) in order to reconstruct the super-resolved
image.
The second mode is to apply a pump beam having a doughnut-like shape which
will yield a central narrow part in the IR beam to pass through, and the rest of the
beam will be blocked (see Fig. 9.12b). Then, no post-processing is required and the
sample is scanned with a narrower probe PSF having Gaussian-like shape. Owing to
the absorption mechanism in both modes, we generate higher spatial frequencies in
the PSF of the probe, which leads to the extraction of the nanometric features of the
sample.
In previous works [33–36] we presented the development of an all-optical silicon
slab temporal data modulator applied on an IR laser probe beam, while the modulation
is generated via a second pulsed green laser pump beam. The pump laser generated
H. Pinhas et al.
two nanostructures since there the described doughnut-like shaping of the PSF will
not occur similar to the Gaussian PSF. Thus, the gap between the two nanostructures
should be smaller than the size of the PSF. Another issue is how the biosample is
placed on top of the nanostructure. To make sure that the probe’s beam will penetrate
into the samples and reach the nanostructure, its chosen wavelength should be long
enough (e.g. near IR) to have sufficient penetration depth.
9.6 Silicon Wafers Imaging
As in the silicon nanostructures concepts described in the earlier sections, the same
approach can be applied on silicon wafers for failure analysis application [32]. As
explained before, an IR laser beam in silicon can be shaped by changing the silicon
complex refractive index locally via another laser beam absorbed in the silicon which
acts as a pump. This change is induced by the change in the free charge carriers (FCC)
density in the silicon due to the absorbed pump beam.
As mentioned earlier, spatial frequencies higher than the ordinary diffractionlimited Gaussian shape PSF frequencies are induced. Moreover, it is important to
note that the proposed mechanism is nonlinear because the absorption coefficient for
the probe is proportional to the power of the pump; therefore the total absorption
of the probe is exponentially related to the absorption coefficient according to the
Beer–Lambert law. Thus, the intensity of the probe is exponentially dependent on
the intensity of the pump. The result of this technique is the improvement in the PSF
of the IR beam.
Here we propose to perform the shaping of the IR beam’s PSF in two modes: First
is to induce a hole at its center. This is generated by applying a narrower Gaussian
pump beam at its center [32], as seen in Fig. 9.12a. For this mode the PSF has a
shape requiring post-processing (decoding) in order to reconstruct the super-resolved
image.
The second mode is to apply a pump beam having a doughnut-like shape which
will yield a central narrow part in the IR beam to pass through, and the rest of the
beam will be blocked (see Fig. 9.12b). Then, no post-processing is required and the
sample is scanned with a narrower probe PSF having Gaussian-like shape. Owing to
the absorption mechanism in both modes, we generate higher spatial frequencies in
the PSF of the probe, which leads to the extraction of the nanometric features of the
sample.
In previous works [33–36] we presented the development of an all-optical silicon
slab temporal data modulator applied on an IR laser probe beam, while the modulation
is generated via a second pulsed green laser pump beam. The pump laser generated