In this work, we present an observation of laser induced periodic surface structures (LIPSS) on graphene. LIPSS on other materials have been observed for nearly 50 years, but until now, not on graphene. Our findings for LIPSS on multi-layer graphene were consistent with previous reports of LIPSS on other materials, thus classifying them as high spatial frequency LIPSS. LIPSS on multi-layer graphene were generated in an air environment by a linearly polarized femtosecond laser with excitation wavelength λ of 840 nm, pulse duration τ of ∼150 fs, and a fluence F of ∼4.3–4.4 mJ/cm². The observed LIPSS were perpendicular to the laser polarization and had dimensions of width w of ∼30–40 nm and length l of ∼0.5–1.5 μm, and spatial periods Λ of ∼70–100 nm (∼λ/8–λ/12), amongst the smallest of spatial periods reported for LIPSS on other materials. The spatial period and width of the LIPSS were shown to decrease for an increased number of laser shots. The experimental results support the leading theory behind high spatial frequency LIPSS formation, implying the involvement of surface plasmon polaritons. This work demonstrates a new way to pattern multi-layer graphene in a controllable manner, promising for a variety of emerging graphene/LIPSS applications.

In this paper we study several temperature sensing techniques using the same thermographic phosphor: luminescence intensity ratio, lifetime, rise time. Moreover, we analyze some recently presented techniques, based on host luminescence intensity ratio method and delayed gate intensity ratio technique. We have selected YVO ₄ :Eu ³⁺ nano powder as an appropriate material for this study, because it has easily detectable luminescence rise time and host luminescence. The material was prepared using simple solution combustion synthesis. The time resolved analysis of emission spectra was achieved using the streak camera system. We present a very detailed analysis of measured lifetimes and rise times of all emission lines and their temperature dependence. We propose a multi-mode temperature sensing technique based on the concept of luminescence detection part of the temperature sensor capable of switching between several measurements modes to obtain the best sensitivity in desired range of operation.