2 Ultrafast Laser Enabling Versatile Fabrication of Surface …
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can both provide Cu surfaces with more effective light trapping effects and consequently reach lower reflectance. For the denser micro cone arrays with nanowires, a
reflectance valley of ~0.6% at around the wavelength of 17 µm has been realized,
which is one of the lowest experimental results reported on metal surfaces to the best
of our knowledge to date. In addition to that, such a near-unity infrared antireflection
property has no obvious wavelength dependence, which is broadband effective with
hemispherical reflectance steadily below 3% attained over the 14–18 µm wavelength
range. In Fig. 2.31b, it is further shown that the average reflectance within the 10–
15, 15–20, and 20–25 µm spectra is all below 10%, indicating that nearly 90% of
surface reflection has been eliminated by the macro-micronano-nanowire multiscale
antireflection structures.
2.7 Applications and Outlook
2.7.1 Photothermal Conversion
As mentioned in Sect. 2.1, we aim to study the photon absorption as well as conversion properties of the metal surface micro-nano structures. It has been shown in the
former sections that SMNS with outstanding antireflection properties over broad
spectrum as well as broad incident angle ranges has been successfully fabricated
through the ultrafast laser-assisted micro-nano structuring approaches we developed. Such extraordinary antireflection properties can greatly enhance the photon
trapping capability of metal surfaces and improve their photo absorption efficiency.
After that, the absorbed photon energies can be utilized through various means,
among which photothermal conversion is one most direct way. In this section, we
take the photothermal conversion process as an application instance of the excellent
antireflection SMNS we fabricated.
Here, we selected four kinds of typical SMNS for comparison. As shown in
Fig. 2.32a–d, when the four kinds of SMNS are produced, the Cu surfaces get darker
gradually from Structure 1 to Structure 4, indicating increased light absorption on Cu
surfaces. Based on the SEM and laser confocal microscope characterizations, these
structures can be classified into two groups. Structures 1 and 2 are constituted of
uniform arrays of micro cones as well as micro holes among them. Both the cones and
holes have clear contours. On the surfaces of the micro cones, there exist plenty of submicro scale features like corrugations and particles. Structure 2 has higher cones and
deeper holes than Structure 1, which is accountable for the contrast in their brightness
under the same SEM conditions. Structures 3 and 4 feature with particles ranging
from nano to micro scales, which distribute randomly and hierarchically on the copper
surfaces and are a highly disordered structural form. Particularly in Structure 4, the
particle architectures are more prominent while the minimum structural features are
105
can both provide Cu surfaces with more effective light trapping effects and consequently reach lower reflectance. For the denser micro cone arrays with nanowires, a
reflectance valley of ~0.6% at around the wavelength of 17 µm has been realized,
which is one of the lowest experimental results reported on metal surfaces to the best
of our knowledge to date. In addition to that, such a near-unity infrared antireflection
property has no obvious wavelength dependence, which is broadband effective with
hemispherical reflectance steadily below 3% attained over the 14–18 µm wavelength
range. In Fig. 2.31b, it is further shown that the average reflectance within the 10–
15, 15–20, and 20–25 µm spectra is all below 10%, indicating that nearly 90% of
surface reflection has been eliminated by the macro-micronano-nanowire multiscale
antireflection structures.
2.7 Applications and Outlook
2.7.1 Photothermal Conversion
As mentioned in Sect. 2.1, we aim to study the photon absorption as well as conversion properties of the metal surface micro-nano structures. It has been shown in the
former sections that SMNS with outstanding antireflection properties over broad
spectrum as well as broad incident angle ranges has been successfully fabricated
through the ultrafast laser-assisted micro-nano structuring approaches we developed. Such extraordinary antireflection properties can greatly enhance the photon
trapping capability of metal surfaces and improve their photo absorption efficiency.
After that, the absorbed photon energies can be utilized through various means,
among which photothermal conversion is one most direct way. In this section, we
take the photothermal conversion process as an application instance of the excellent
antireflection SMNS we fabricated.
Here, we selected four kinds of typical SMNS for comparison. As shown in
Fig. 2.32a–d, when the four kinds of SMNS are produced, the Cu surfaces get darker
gradually from Structure 1 to Structure 4, indicating increased light absorption on Cu
surfaces. Based on the SEM and laser confocal microscope characterizations, these
structures can be classified into two groups. Structures 1 and 2 are constituted of
uniform arrays of micro cones as well as micro holes among them. Both the cones and
holes have clear contours. On the surfaces of the micro cones, there exist plenty of submicro scale features like corrugations and particles. Structure 2 has higher cones and
deeper holes than Structure 1, which is accountable for the contrast in their brightness
under the same SEM conditions. Structures 3 and 4 feature with particles ranging
from nano to micro scales, which distribute randomly and hierarchically on the copper
surfaces and are a highly disordered structural form. Particularly in Structure 4, the
particle architectures are more prominent while the minimum structural features are