Abstract
In this paper, we report on the time-dependent strain-wave-induced changes in the reflection and diffraction of a gold plasmonic grating. We demonstrate efficient excitation of strain waves using enhanced absorption at and around the surface plasmon polariton resonance. In addition, we observe that the strain-wave-induced changes in the reflection and diffraction of the grating show an approximately quadratic dependence on pump fluence when probed at a wavelength of 400 nm. We tentatively attribute this non-linear behavior to strain-induced nonlinear changes of the interband transition energy. Using a model that calculates the permittivity of the gold taking into account the d to s/p interband transition, we deduce that the interband transition energy would have to change by about 0.013 eV to account for the measured changes in reflection.
Highlights
The ability of ultrafast lasers to generate strain waves in thin metal layers has been investigated extensively in the past.1–3 Compared to light, the advantage of laser-induced strain waves is that they can travel through optically opaque materials, giving access to a multitude of material properties and physical phenomena.4–22 Laserinduced strain waves find applications in many fields, such as the detection of buried structures23–27 and photo-acoustic imaging.28,29 They show promise for applications in the semiconductor manufacturing industry for wafer alignment
We showed that the detection of laserinduced strain waves can be enhanced by probing the effect that they have on a surface plasmon polariton (SPP) resonance
For all pump-probe measurements discussed below, the beam diameters at the surface of the sample of both pump and probe were kept constant with a full width at half maximum (FWHM) beam diameter of 600 and 300 μm, respectively
Summary
The ability of ultrafast lasers to generate strain waves in thin metal layers has been investigated extensively in the past. Compared to light, the advantage of laser-induced strain waves is that they can travel through optically opaque materials, giving access to a multitude of material properties and physical phenomena. Laserinduced strain waves find applications in many fields, such as the detection of buried structures and photo-acoustic imaging. They show promise for applications in the semiconductor manufacturing industry for wafer alignment. The advantage of laser-induced strain waves is that they can travel through optically opaque materials, giving access to a multitude of material properties and physical phenomena.. Laserinduced strain waves find applications in many fields, such as the detection of buried structures and photo-acoustic imaging.. Laserinduced strain waves find applications in many fields, such as the detection of buried structures and photo-acoustic imaging.28,29 They show promise for applications in the semiconductor manufacturing industry for wafer alignment. The presence of strain waves can be detected by measuring changes in the optical properties of the material or by measuring the physical displacement of surfaces and interfaces caused by these waves. There is a clear need to enhance the optical response to laser-induced strain waves
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