【作者】 高震森；

【导师】 李淳飞；

【作者基本信息】 哈尔滨工业大学 ， 光学， 2008， 硕士

【摘要】 光速控制是近年来光子学领域的一个研究热点,人们先后在冷原子蒸汽、红宝石晶体和半导体量子点等介质中实现了光速控制。由于其在光学延迟线、全光缓存、全光开关等方面的潜在应用,在光纤与微环波导中实现光速控制更具有实际意义。本论文详细研究了在光纤中利用相干布居数振荡、受激布里渊散射和光纤参量放大技术实现光速的控制,另外,还探讨了在微环波导中的光速控制方法。相干布居数振荡技术具有结构简单,易于实现的特点,而且利用掺饵光纤可以实现对通信波长1550nm的光速控制。以半经典理论和速率方程理论为基础,理论研究了信号光功率、光纤长度和掺杂浓度对1550nm信号光自延迟效应的影响以及利用980nm泵浦光对信号光群速度的控制。在10m长的掺饵光纤中,实验观察到了最大延迟时间为7.2ms,对应的最小群速度为1.39×103m/s。通过加入980nm泵浦光来调节相干布居数,在泵浦功率为50mW以上时,观察到了慢光向快光的转变,成功实现了利用泵浦光功率来控制信号光的群速度的目的,实验结果与理论预言相一致。受激布里渊散射是一种三阶非线性效应,由于其阈值较低,在光纤中较易实现,但是其增益带宽较窄,不利于实际应用。通过采用泵浦增宽和双泵浦激光技术,即可增加其带宽和减小脉冲畸变。另外,本文提出利用光纤参量放大技术在小信号增益情况下实现对信号光群速度的控制。通过改变泵浦光功率或泵浦波长,可实现对ps量级脉冲的光速控制,这种技术有可能应用于传输速率为Gbit/s的光纤通信系统中。最后,根据波导耦合方程,本文系统地理论研究了基于单环、双环和串联微环波导的光速控制特性。研究表明,单个微环波导在谐振状态时可以实现慢光和快光,但其透射率较低,如利用双环结构,则可以弥补这一缺陷,在对光速控制的同时,实现高透射;串联微环结构具有光子带隙特征,在带隙中心处,当环间耦合系数较小时,随着环数的增加,群速度逐渐减小;在光子带边处,群延时迅速变大,光速控制效果显著增强,这为实际利用微环波导制作光速控制器件奠定了理论基础。更多还原

【Abstract】 Group velocity control is of great research interest in the area of photonics during the last several years, and many researchers have realized it in the cold atom, ruby, semiconductor quantum dots and so on. However, the optical fiber and ring resonator optical waveguide have attracted much attention due to their potential applications in the area of optical delay line, optical buffer and optical switching. This dissertation presents a numerical and experimental study on the group velocity control based on the coherent population oscillation, stimulated brillouin scattering and optical parametric amplification in the optical fiber and ring resonator optical waveguide.Coherent population oscillation exhibits several merits such as simple configuration, easy implementation and able to control the pulse in the 1550nm telecommunication window. We theoretically studied the influence of signal power, fiber length, doped ion concentration on the self-delay effect of the signal pulse and the group velocity control using an additional 980nm pump laser. We observed a maximum delay of 7.2ms corresponding to the slowest group velocity of 1.39×103m/s in an Er3+ doped fiber of 10m. We then used the 980nm pump to tune the coherent population, and observed the transition process from slow light to fast light when the pump power is over 50mW. We successfully realized the idea of control the group velocity of the signal light by the pump power of another light and the experimental result consistent with the theory prediction very well.Stimulated brillouin scattering is a third-order nonlinear effect, and it is easy to be generated in optical fiber because of the low threshold. However, this technique is not suitable for practical application due to the low gain bandwidth. By broadening the pump spectrum or using the two pump laser techniques, the bandwidth can be greatly increased and the pulse distortion can be alleviated as well. Additionally, we proposed a new technique to control the group velocity based on the fiber optical parametric amplification in the small signal regime. We can tune the group velocity of a pulse with picosecond width only by tuning the pump power or wavelength which may find its application in the optical communication system with transmission data-rate of Gbit/s.Finally, we studied the group velocity control based on the single ring resonator, two ring resonators, and coupled ring resonators optical waveguide based on the waveguide coupled-mode equation. The numerical results shown that although the single ring resonator can realize slow and fast light when it is tuned on resonance, the amplitude transmission is too low to be used in practical but it can be made up by the two resonators which can also control the group velocity very well with high transmission. The coupled ring resonators exhibit photonic band gap characteristic and the larger the number of the rings, the more group delay we can achieve when the coupling coefficients is rather small in the center of the pass band. The group velocity control can be greatly enhanced on the edge of the band gap. All the above mentioned theory laid a solid foundation for the fabrication of ring resonator to control the group velocity.更多还原