Search

Abstract Commercially available polymer films of a particular brand (Desmat CT100), identified as Polyethylene Terephthalate (PET), was shown to be very effective as Nuclear Track Detectors (NTDs) with a very high detection threshold (Z/ β ≈ 140). It makes this particular brand of PET films an ideal choice as an NTD for rare event (e.g. strangelets) search in cosmic rays as well as in particle accelerators. Charge response and other properties of PET films from different batches of the Desmat CT100 brand as well as PET films from two other manufacturers, Plus Print and Office Plus were studied to check for consistency. Those studies show no significant difference among different batches of PET films for the Desmat CT100 brand. But statistically significant differences in charge response are seen between PET films from different manufacturers despite similarities in their chemical composition. Highlights • Charge response of PET films (used as NTDs for rare event search) from three different manufacturers were checked for consistency. • Those studies show no significant difference among different batches of PET films for the Desmat CT100 brand. • But statistically significant differences in charge response are seen between PET films from different manufacturers. • Shows the need to stick to one particular brand of films for large area NTD arrays. [ABSTRACT FROM AUTHOR]

A unique delay-dependent dynamic switching of optical nonlinearity in terms of saturation absorption (SA) and excited state absorption (ESA) in graphene oxide (GO) and reduced graphene oxide (RGO2 and RGO100) is achieved with an optical pump and white light super-continuum probe only above a threshold pump intensity. Infrared and chemical reduction are used to obtain RGO2 and RGO100 respectively. The switching regime of probe wavelength can be modulated by varying either pump wavelength or degree of reduction. When pumped at 415 nm, the threshold pump intensity to obtain switching property decreases to 9 GW/cm 2 for RGO2 from 18 GW/cm 2 in GO and the tunability range shifts from 471 to 526 nm for as grown GO to 519–623 nm in maximally reduced RGO2. Though the saturation intensity of intrinsic non-degenerate two photon absorption (nd-TPA) is found to be lower in GO (4.3 GW/cm 2 ) than RGO2 (18.2 GW/cm 2 ), nd-TPA coefficient increases from 0.0015 cm/GW (GO) to 0.0026 cm/GW (RGO2) with increasing reduction. The detailed kinetics of the scattering processes show variation as a function of pump power, probe wavelength and degree of reduction. A model band diagram based on amorphous-carbon model and a Tauc analysis are used to explain the unusual nonlinear optical properties. [ABSTRACT FROM AUTHOR]

Femtosecond (fs) laser excited second harmonic (SH) and multiphoton absorption (MPA) induced UV luminescence generation behaviour of Zinc oxide (ZnO) nanofibers is reported here. The used nanofibers are grown by seed assisted chemical bath deposition technology over glass substrates and are excited by a near-infrared (NIR) Ti: Sapphire laser emitting pulses of wavelength 812 nm and duration 100 fs. The peak wavelength of SH and MPA induced UV luminescence signals are found to be 406 nm and 398 nm respectively. Due to good optical quality, no defect level related MPA induced visible luminescence is observed in nanofibers. In comparison to this, ZnO nanostructures grown over plane substrate without seed layer shows very less SH and MPA induced UV luminescence. However in this case, the defect level related MPA induced visible luminescence was found to be very high. Applications like ultrafast pulse diagnostics, NIR induced photodynamic therapy etc. require high SH and MPA induced UV luminescence and low defect level related visible luminescence. So the ZnO nanofibers can be a potential candidate for these applications. [ABSTRACT FROM AUTHOR]