Gao Feng, Wang Yang, Xu Liang, Feng Zhenhua, Wu Qiong, Zhang Baohui, Liu Jingyao, Tang Jiang, Tang Ming, Liu Huan, Fu Songnian, Ruan Yinlan, Ebendorff-Heidepriem Heike, Liu Deming
Opt Express. 2018 Feb 19;26(4):3903-3914. doi: 10.1364/OE.26.003903.
The development of highly efficient light-controlled functional fiber elements has become indispensable to optical fiber communication systems. Traditional nonlinearity-based optical fiber devices suffer from the demerits of complex/expensive components, high peak power requirements, and poor efficiency. In this study, we utilize colloidal quantum dots (CQDs) to develop a light-controlled optical fiber interferometer (FI) for the all-optical control of the transmission spectrum. A specially designed exposed-core microstructure fiber (ECMF) is utilized to form the functional structure. Two types of PbS CQDs with absorption wavelengths around 1180 nm and 1580 nm, respectively, are deposited on the ECMF to enable the functional FI. The wavelength and power of control light are key factors for tailoring the FI transmission spectrum. A satisfactory recovery property and linear relationship between the spectrum shift and the power of control light at certain wavelength are achieved. The highest wavelength shift sensitivity of our light-controlled FI is 4.6 pm/mW, corresponding to an effective refractive index (RI) change of 5 × 10 /mW. We established a theoretical model to reveal that the RI of the CQD layer is governed by photoexcitation dynamics in CQD with the light absorption at certain wavelength. The concentration of charge carriers in the CQD layer can be relatively high under light illumination owing to their small size-related quantum confinement, which implies that low light power (mW-level in this work) can change the refractive index of the CQDs. Meanwhile, the absorption wavelength of quantum dots can be easily tuned via CQD size control to match specific operating wavelength windows. We further apply the CQD-based FI as a light-controllable fiber filter (LCFF) in a 50-km standard single-mode fiber-based communication system with 12.5-Gbps on-off keying direct modulation. Chirp management and dispersion compensation are successfully achieved by using the developed LCFF to obtain error-free transmission. CQDs possess excellent solution processability, and they can be deposited uniformly and conformally on various substrates such as fibers, silicon chips, and other complex structure surfaces, offering a powerful new degree of freedom to develop light control devices for optical communication.
高效光控功能光纤元件的发展已成为光纤通信系统不可或缺的一部分。传统的基于非线性的光纤器件存在组件复杂/昂贵、峰值功率要求高以及效率低等缺点。在本研究中，我们利用胶体量子点（CQD）开发了一种用于全光控制传输光谱的光控光纤干涉仪（FI）。采用一种特殊设计的裸芯微结构光纤（ECMF）来形成功能结构。分别将两种吸收波长约为1180 nm和1580 nm的PbS CQD沉积在ECMF上，以实现功能化的FI。控制光的波长和功率是调整FI传输光谱的关键因素。在特定波长下，实现了令人满意的恢复特性以及光谱位移与控制光功率之间的线性关系。我们的光控FI的最高波长位移灵敏度为4.6 pm/mW，对应于5×10⁻⁵ /mW的有效折射率（RI）变化。我们建立了一个理论模型来揭示CQD层的RI受CQD中光激发动力学以及特定波长下光吸收的支配。由于其与尺寸相关的小量子限制，CQD层中的电荷载流子浓度在光照下可以相对较高，这意味着低光功率（本工作中为毫瓦级）就可以改变CQD的折射率。同时，量子点的吸收波长可以通过控制CQD尺寸轻松调整，以匹配特定的工作波长窗口。我们进一步将基于CQD的FI应用于基于50 km标准单模光纤且采用12.5 Gbps开关键控直接调制的通信系统中作为光控光纤滤波器（LCFF）。通过使用所开发的LCFF成功实现了啁啾管理和色散补偿，从而获得无误码传输。CQD具有出色的溶液加工性，并且它们可以均匀且保形地沉积在各种基材上，如光纤、硅芯片和其他复杂结构表面，为开发用于光通信的光控器件提供了一个强大的新自由度。
