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Frontiers in Guided Wave Optics and Optoelectronics Part 11

Tham khảo tài liệu 'frontiers in guided wave optics and optoelectronics part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 19 Optical Deposition of Carbon Nanotubes for Fiber-based Device Fabrication Ken Kashiwagi and Shinji Yamashita Department of Electronic Engineering The University of Tokyo Japan 1. Introduction Since carbon nanotubes CNTs have been applied to a passive mode-locker or a saturable absorber Set et al. 2004a Set et al. 2004b applications of CNTs in photonics field have been intensively investigated. Their quasi-one-dimensional structures produce their distinctive characteristics their strong third-order nonlinearity and ultrafast recovery time shorter than 1ps Chen et al. 2002 Ichida et al. 2002 . These characteristics are attractive for future ultrafast photonic networks and can be used in ultrafast photonic devices such as ultrafast all-optical switches and all-optical logic gates. Since CNTs are nano-sized material one of the largest problems to realize CNT-based devices is handling issue. Optical deposition method has an advantage in efficiency over the other handling methods such as spraying Set et al. 2004a Set et al. 2004b direct synthesis Yamashita et al. 2004 and polymer embedding methods Sakakibara et al. 2005 . These methods mostly require complicated processes large-scale setups and dissipate significant numbers of CNTs. A simpler and more cost effective handling technique of CNTs is required for mass productive CNT-based optical devices. We proposed optical CNT deposition technique to solve the problem. The light injection into CNT-dispersed solution from an optical fiber end deposited CNTs onto core region of the optical fiber end. We realized a passively mode-locked fiber laser using the CNT-deposited fiber as a saturable absorber or a passive mode-locker. However the technique requires very precise control of the light injection power to deposit uniform and less scattering CNT layer because highly uniform CNT solution which has very small CNT entanglements is required. Smaller CNT entanglements require higher injection power. High power injection makes