Palestrante
Descrição
Graphene oxide (GO) has gained attention in the graphene family owing to its optical and electrical properties.(1) Moreover, it is low-cost and water-soluble compared to graphene, thus holding a great potential for large-scale and cost-effective production of graphene-based materials. GO-based composites have been exploited for several applications, including ultrafast lasers, optical limiting and multimode optical recording and have been realized mostly in thin films.(2) However, the development of GO-based composites from polymers used for direct laser writing, which would enable the fabrication of 3D photonic micro/nanodevices, has been far less explored. In this work, we investigate the mechanisms underlying a mode filtering effect observed in polymer microcavities containing graphene oxide aiming at the development of on-chip integrable photonic devices. We have fabricated the microcavities by means of two-photon polymerization via direct laser writing.(3) They exhibit good structural quality and smooth sidewall surfaces (cavity loaded Q-factor of 2×10$^4$ at 1550 nm). The presence of graphene oxide in the microcativities is confirmed by Raman spectroscopy. To investigate the influence of saturable absorption in the GO-doped microcavities, we carried out nonlinear measurements through the femtosecond Z-scan technique with excitation at 1550 nm. By modeling the photo-carrier dynamics with a two-level system, we found the saturation intensity to be 500 MW/cm$^2$, which is three orders of magnitude higher than the intracavity intensity achieved with the pump levels employed to excite the microcavities. This result shows that the mode filtering effect may be prompted by other mechanisms. We have been currently studying the influence of thermal optical nonlinearities by Z-scan technique carried out with continuous-wave excitation and our preliminary results suggest that laser-induced thermal lens effects may be playing a major role in the mode filtering observed in the GO-doped polymer microcavities.
Referências
1 BONACCORSO, F. et al, Graphene photonics and optoelectronics. Nature Photonics, v. 4, n. 9, p. 611-622, 2010.
2 STANKOVICH, S. et al, Graphene-based composite materials.Nature, v. 442, n. 100, p. 282-286, 2006.
3 TOMAZIO, N. B. et al. Femtosecond laser fabrication of high-Q whispering gallery mode microresonators via two-photon polymerization. Journal Polymer Scence Part B: polymer Physics, v. 55, n.7,p. 569-574, 2017.
| Apresentação do trabalho acadêmico para o público geral | Sim |
|---|---|
| Subárea | Óptica e Lasers |
