CC BY
12LD-I-2
Surface enhanced spectroscopy and sensing enabled by femtosecond-laser-printed plasmonic metasurfaces
Aleksandr Kuchmizhak'-2
1-Institute of Automation and Control Processes FEB RAS, 5 Radio Str., 690041 Vladivostok, Russia 2-Far Eastern Federal University, 6 Sukhanova Str., 690041 Vladivostok, Russia
Ultrafast deposition of energy of a tightly focused femtosecond (fs) laser pulse into the thin substrate-supported noble metal films initiates a sequence of physical processes that start from a local solid-liquid transition following by surface morphology modification and resolidification. As a result of single-pulse fs-laser irradiation at below-threshold fluence, the unique 3D surface morphologies - nanobumps and nanojets - can be imprinted on the surface of the noble-metal films [1]. Within a certain range of laser processing parameters, formation of such 3D plasmonic nanostructures proceeds without ablation (i.e. ejection and redeposition of any material) resulting in extremely good printing reproducibility. This feature allows realization of novel practically relevant designs of plasmonic metasurfaces consisting of ordered arrays of nanobump and nanojets. Here, we highlight our recent results related to optical, nonlinear optical and sensing application of such laser-printed plasmonic metasurfaces, in particular, for tailoring spontaneous emission of IR-emitting HgTe quantum
Figure 1. (a) Diffuse reflectance spectra of MIM sandwich (red curve) and bare 50-nm thick Au film on a glass substrate (yellow curve). (b) Series of side-view SEM images of the MIM surface textured at elevated pulse energy (from 1.1 to 1.8 nJ). (c) Corresponding bright-field optical image of the square-shape laser-patterned areas (200 x 200 ^m2) processed at elevated pulse energies E as well as reflectance spectra (d) of these areas. (e) HCV color space with markers indicating the colors of the pristine MIM sandwich
and the patterned areas from (c). (f) Bright-field optical image of the laser-patterned area (E=1.8nJ) visualized with microscope objective at NA=0.3 and 0.8. (g) Bright-field optical image of the patterned area (400 x 80 ^m2) arranged to form "FEFU" letters. The nanobumps were imprinted at pulse energy E=1.8 nJ and periodicity of 1 ^m.
dots [2], enhancement of second-harmonic generation [3], as well as for molecular and gas sensing based of surface-enhanced IR absorption [4]. Finally, we demonstrate that by patterning the top layer of a metal-insulator-metal (MIM) sandwich designed to support Fabry-Perot mode in the visible spectral range with the nanobumps and nanojets one can realize facile strategy for high-resolution color printing (Fig. 1a). We found that by changing the 3D shape of the nanobumps and nanojets through variation of the pulse energy and beam focusing conditions one can gradually tune the reflected color from reddish brown to pure green (Fig. 1b-f). Up-scalable ablation-free laser fabrication method paves the way towards various applications ranging from large-scale structural color printing to optical sensors and security labeling at a lateral resolution of 25,000 dots per inch.
[1] F. Korte, et.al., Towards nanostructuring with femtosecond laser pulses, Applied Physics A 77 (2), 229-235 (2003).
[2] A.A. Sergeev, et.al., Tailoring spontaneous infrared emission of HgTe quantum dots with laser-printed plasmonic arrays, Light: Science & Applications 9 (1), 1-10 (2020).
[3] A.B. Cherepakhin, et.al., Laser-printed hollow nanostructures for nonlinear plasmonics, Applied Physics Letters 117 (4), 041108 (2020).
[4] D Pavlov, et.al., Coaxial hole array fabricated by ultrafast femtosecond-laser processing with spatially multiplexed vortex beams for surface enhanced infrared absorption, Applied Surface Science 541, 148602 (2021).
