We report on the first experimental study of the layer-to-layer compression and enhanced optical properties of few-layer graphene nanosheet by applying ion irradiation. The deformation of graphene layers is investigated both theoretically and experimentally. It is observed that after the irradiation of energetic ion beams, the space between separate graphene layers is reduced due to layer-to-layer compression, resulting in tighter contact of the graphene sheet with the surface of the substrate. This processing enables enhanced interaction of the graphene with the evanescent-field wave near the surface, which induces reinforced polarization-dependent light absorption of the graphene. Utilizing the ion-bombarded graphene nanosheets as saturable absorbers, we have realized efficient Q-switched waveguide lasing with enhanced performance through the interaction of the graphene and evanescent field.
We report on the guided-wave second-harmonic generation in a KTiOPO4 nonlinear optical waveguide fabricated by a 17 MeV O5+ ion irradiation at a fluence of 1.5×1015 ions/cm2. The waveguide guides light along both TE and TM polarizations, which is suitable for phase-matching frequency doubling. Second harmonics of green light at a wavelength of 532 nm have been generated through the KTiOPO4 waveguide platform under an optical pump of fundamental wave at 1064 nm in both continuous-wave and pulsed regimes, reaching optical conversion efficiencies of 5.36%/W and 11.5%, respectively. The propagation losses have been determined to be ∼3.1 and ∼5.7 dB/cm for the TE and TM polarizations at a wavelength of 632.8 nm, respectively.
Structural, magnetic, and magneto-transport properties in C:Ni (30 at.%) nanocomposite films grown by ion
beam cosputtering at 500 °C are investigated by means of transmission electron microscopy, superconducting
quantum interference device magnetometry and electrical transport measurements. The C:Ni film shows a
superparamagnetic behavior with a large coercivity field of 250 Oe at 5 K compared with bulk Ni metals.
Anomalous Hall effect is observed in C:Ni nanocomposites, which is attributed to the scattering of spin-polarized
carriers by the magnetic Ni nanoparticles in the carbon matrix.