We demonstrate, for the first time, high-order harmonic generation from C60 by an intense femtosecond Ti:sapphire laser. Laser-produced plasmas from C60-rich epoxy and C60 films were used as the nonlinear media. Harmonics up to the 19th order were observed. The harmonic yield from fullerene-rich plasma is about 25 times larger compared with those produced from a bulk carbon target. Structural studies of plasma debris confirm the presence and integrity of fullerenes within the plasma plume, indicating fullerenes as the source of high-order harmonics.

We studied high-order harmonic generation from plasma that contains an abundance of indium oxide nanoparticles. We found that harmonics from nanoparticle-containing plasma are considerably more intense than from plasma produced on the In2O3 bulk target, with high-order harmonic energy ranging from 6 μJ (for the ninth harmonic) to 1 μJ (for the 17th harmonic) in the former case. The harmonic cutoff from nanoparticles was at the 21st order, which is lower than that observed using indium oxide solid target. By comparing the harmonic spectra obtained from solid and nanoparticle indium oxide targets, we concluded that intense harmonics in the latter case are dominantly generated from neutral atoms of the In2O3 nanoparticles.

We show experimental evidence that, for the intense high-order harmonics from nanoparticles, there is a strong contribution from neutral atoms. We present the results of studies on the harmonics generated in laser-produced plasmas containing various nanoparticles, including Cr2O3, In2O3, Ag, MnTiO3, Sn, Cu, and Au. These results are compared with the harmonics generated from plasma produced on the surface of bulk targets. The harmonic spectrum from nanoparticle and bulk In2O3 show that there is a lack in the resonant enhancement of the 13th harmonic for the former. Along with the relatively low cut-off for nanoparticle harmonics, these results show that it is the neutral atom in the nanoparticle that emits the intense harmonics. Structural studies of plasma debris confirm the presence and integrity of nanoparticles in the plasma plumes.

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This paper presents the study of the performance of a novel SU-8 waveguide on a quartz substrate for evanescent fluorescence spectroscopy. The sensitivity of the sensing platform (SU-8/quartz) was compared to an SU-8 waveguide on silica fabricated with the standard protocol. The physical properties of the SU-8/quartz waveguide resulting from a novel fabrication process allowed for a higher fluorescence coupling and lower optical losses than the SU-8/silica waveguide. The impact of the different indices of refraction of both waveguides on the fluorescence collection efficiency was calculated with three-dimensional finite-difference time-domain simulations by simulating randomly oriented and phased dimensionless current dipoles in the vicinity of their sensing layers. An evanescent fluorescence spectroscopy experiment was performed with different concentrations of Alexa-647 labeled-BSA proteins immobilized on the two polymer waveguides to compare the sensitivity of both sensing platforms. The SU-8/quartz waveguide revealed to have a higher calculated fluorescence collection efficiency and also a greater measured fluorescence light output compared to the SU-8/silica waveguide.