光学谐振系统中慢光特性研究

针对两环形腔与直波导耦合的系统,考虑光纤耦合器的插入损耗,发现两个耦合器反射值的不同匹配,却可以在谐振处得到相同的透过率峰值,因此可以不必限定某两个具体反射值,通过数值模拟得到中心频率处透过率峰值与群折射率的反比关系.由于群延迟与群折射率相对应,所以群延迟的增加势要以牺牲峰值透过率为代价.将增益介质加入到三环形腔与直波导耦合的系统中,可以使结构的色散响应由反常色散转化为正常色散,同样体现出慢光的特性.在频域和时域范围内分别对群延迟做了定量的分析. 关键词： 慢光 透过率 有效相移 群延迟     

一种包含非线性光学效应的硅基微环稳态模型

微环谐振器是集成光学中的关键器件,它的实际滤波特性会受到输入光功率的影响,但长期以来,微环谐振器的稳态模型仅包含线性光学作用。考虑微环谐振器反馈波导中的光学非线性引入的损耗和相移,以及微环耦合器中光学非线性引入的耦合比改变等因素,推导了考虑自相位调制、双光子吸收和热光效应的微环谐振器的非线性模型。重点讨论了双光子吸收和光学非线性引入的耦合器耦合比改变对微环谐振器陷波深度的影响,仿真结果表明,在热光效应和自相位调制产生谐振谱线频移的同时,功率相关的耦合器耦合比的改变对微环谐振器陷波深度的影响较大。     

微环耦合谐振光波导中的色散控制模型与数值仿真

本文利用传输矩阵法得到了微环耦合谐振光波导的色散关系,讨论了耦合损耗、传输损耗及耦合系数对微环耦合谐振光波导色散的影响,改变耦合损耗、传输损耗及耦合系数可控制其色散曲线的形状、位置、以及带宽,色散曲线的变化及控制对微环耦合谐振光波导在滤波、光信号延迟及缓存等方面的应用有重要意义. 关键词： 光波导 微环光波导 传输矩阵法     

光脉冲在微环耦合谐振光波导中传输线性特性的数值仿真

利用传输矩阵法得到了微环耦合谐振光波导色散关系的一般表达式,并由色散关系出发讨论了光脉冲在微环耦合谐振光波导中传输时的线性特性,包括带宽、群速度、色散和线性相位变化,这些特性对微环耦合谐振光波导在光通信和光传感领域的应用有重要意义. 关键词： 微环光波导 光脉冲线性特性 传输矩阵法 数值仿真     

基于新型三环谐振器的诱导透明效应分析

针对谐振式微腔的应用需求, 提出了一种新型三环谐振式微腔结构, 类似于原子系统中的电磁诱导透明, 耦合诱导透明(CRIT)效应在一个新的光学微腔系统中已被实验证明. 该结构在硅基上由三个尺寸完全一样的微环腔组成, 通过理论分析、制备和实验测试, 能够观察到CRIT现象, 其频谱具有低群速的狭窄透明峰, 与光栅耦合器的耦合效率为34%, 并且谐振器的品质因数达到了0.65×10⁵, 同时, 失谐的谐振波长可以通过温度变化来控制, 这在旋转传感、光滤波器、光存储器等方面的应用有重要意义.     

一种改进的2×2 SOI Mach-Zehnder热光开关

本文设计并制作了基于强限制多模干涉耦合器的2×2 SOI马赫-曾德热光开关.这种光开关采用了深刻蚀结构的多模干涉耦合器和输入/输出波导,较大地提高了干涉耦合器的性能并减少了连接耦合损耗.同时,在调制臂区域采用浅刻蚀结构,保持其单模调制状态.深刻蚀多模干涉耦合器具有优越的特性,在实验中测得不均衡度只有0.03 dB,插入损耗－0.6 dB.基于这种耦合器的新型热光开关,其插入损耗为－6.8 dB,其中包括光纤-波导耦合损耗－4.3 dB,开关时间为6.8 μs.     

集成马赫-曾德尔热光耦合器的可调谐振环优化设计

根据耦合模理论,推导出可调谐光波导谐振环的光强和相位传递函数的表达式,并分析了可调谐谐振环的传输特性.结果表明,谐振环中集成的马赫-曾德尔耦合器的参量设定和调谐方式直接影响谐振环的谐振频率移动范围和调制功率.通过改变耦合器参量对谐振环进行优化设计,在中心波长为1550 am附近,谐振环半径2 cm,传输损耗0.08 dB/cm的情况下,实现了清晰度和最佳谐振深度的调谐,谐振频率的移动范围低于0.027 GHz,降低了谐振环对频率调制器的调频要求,同时降低了耦合器的调制功率.     

平面环形谐振腔微光学陀螺结构设计与优化

提出具有高群有效折射率的双环级联作为核心元件的谐振式平面光波导陀螺结构, 基于光学Sagnac原理得到了双微环耦合谐振式光学陀螺理论灵敏度与群有效折射率的一般表达式和双环与单环陀螺系统的灵敏度关系, 并由耦合模理论方法得到了双环系统耦合器的两个透射系数对应的群有效折射率变化情况. 在环腔半径R₁=R₂=100 μm、环腔传输损耗系数t₁=t₂=0.95的情况下, 针对环与环之间耦合器和环与波导之间耦合器透射系数对群有效折射率的不同影响, 得到了最大群有效折射率的产生条件. 采用文中参数(R=100 μm, t=0.95)计算的单环谐振式陀螺灵敏度为(10⁴-10⁵)°/h, 而双环级联谐振系统理论灵敏度能够达到10 °/h. 该研究对微环耦合谐振腔在角速度检测上的应用有重要的意义.     

具有高阶耦合色散系数三芯光纤耦合器非线性光开关特性的研究

利用两种方法研究了高速光脉冲在具有交叉相位调制的等边三角形排列结构的非线性三芯光纤耦合器中传输和开关特性.首先利用变分原理得到三纤芯中传输转移系数随距离变化的方程,然后利用分裂步长傅里叶方法求得了光脉冲的数值解.变分法和数值模拟的结果表明：当一阶模间色散系数较小时,光脉冲仍能在三芯之间周期性耦合传输,并且表现出良好的开关特性,但是随着一阶模间色散系数的增大,脉冲耦合传输的周期性和陡峭的开关特性都遭到破坏,光脉冲在传输中发生分裂;二阶耦合色散系数和初始啁啾都能使光脉冲传输时的耦合长度变短、光脉冲在三纤芯之间 关键词： 三芯光纤耦合器 模间色散系数 耦合长度 开关阈值功率     

用于光纤激光器阵列锁相的光纤环特性研究

光纤环特性对基于公共光纤环的光纤激光器锁相阵列的性能具有重要影响.介绍了利用公共光纤环构建光纤激光器锁相阵列的结构、特征以及光纤环的作用.建立了研究该光纤环特性的理论模型,分别采用光强叠加和光场叠加法分析了光纤环的能量传输与谐振选模特性,并在考虑输入光波谱宽的情况下证明了两种方法的一致性.研究表明增加成环耦合器的耦合比可以增强锁相阵列各单元激光器间的能量耦合,且在光纤环损耗较低时不会明显降低输出功率和组合效率.实验中观察到了光纤环的滤波选模效应,而输出功率随着耦合比的增加有规律的略微减小.两者均与理论分析结果一致.     

Control of slow light in a ring-out-ring structure

This paper proposes a ring-out-ring structure of coupled optical resonators to yield coupled-resonator-induced transparency (CRIT). Considering the insertion loss of the coupler,it theoretically deduces the transmission and the effective phase shift. The influences of the insertion loss of the coupler on the transmittance,the effective phase shift,the group index and the CRIT linewidth are fully studied. We find that the increase in multiple m can effectively enhance the normal dispersion and the group index of the proposed structure. Moreover,the specific expression of the group index at resonance is theoretically deduced and discussed for the proposed structure with two rings. The result shows that the multiple m between the lengths of ring 1 and ring 2 can enhance the group index to m times that of the structure with two equal-sized rings at resonance. The control of slow light in the proposed structure is important for applications of highly sensitivity gyroscopes,optical delay lines and optical buffers,etc.     

Integrated ferroelectric millimeter-wave phase shifters with a periodic structure

Integrated phase shifters with a periodic structure that includes BaSrTiO₃ ferroelectric varactors parallel-and series-connected to the transmission line are investigated theoretically and experimentally. The phase shifters are designed for the frequency range 26–32 GHz. The dispersion characteristics and insertion losses in the transmission line of the phase shifters are analyzed with regard to the dependence of the capacitance and loss tangent of the varactors on control voltage and temperature. It is shown that parasitic amplitude modulation in the phase shifters can be suppressed if the connection scheme of the varactors takes into account the voltage dependence of the their loss tangent. In the phase shifters with series-connected varactors, the temperature dependence of the phase shift is much weaker than in those with parallel-connected varactors.     

基于二维多模干涉效应的N×N光开关模型

报道了由两个N×N三维多模干涉耦合器和一段阵列相移波导组成的三维光开关.首先利用导模传输法分析了三维多模干涉耦合器的一般成像原理,并推导出了其成像位置以及相位矩阵.在此基础上,通过场传输矩阵法建立了光开关的传输方程.利用该传输方程计算得到了光开关工作时,阵列相移波导的相位条件,并通过三维有限差分光束传输法进行仿真验证,给出了光开关工作时的插损、串扰指标,以及光开关输出功率随相移波导相位变化的关系.     

泵浦光和信号光之间的相位漂移对级联PSA光传输系统传输性能影响的研究

本文研究相敏光放大器(PSA)中泵浦光相位不能完全跟踪信号光相位时,即两者之间存在相位漂移时,对以PSA作为光中继放大器的高速光纤通信系统传输性能的影响.通过计算机系统仿真,我们得到在不同的相位漂移下,高速信号脉冲眼图劣化度随光纤色散变化的曲线,以及不同传输速率下信号眼图劣化度随放大器相位漂移量变化的曲线.由仿真结果可知,如相位漂移控制在一定范围内,其对系统性能几乎没有影响.但超出此范围时,则系统性能迅速劣化.     

Control of dispersion in fiber coupled resonator-induced transparency structure

Induced transparency phenomena and strong dispersion can be produced in a coupled resonator induced transparency(CRIT) structure.In this paper,we investigate the influences of structure parameters,such as amplitude reflection coefficient and loss,on transmission spectrum and dispersion of CRIT structure,and further study the control of dispersion in the structure.The results show that in the CRIT structure,adjusting the loss of resonators is an effective method of controlling dispersion and producing simultaneous normal and abnormal dispersion.When we choose approximate amplitude reflection coefficients of the two couplers,the decrease of transmittance due to loss could be effectively made up.In the experiment,we achieve the control of dispersion and simultaneous strong normal and abnormal dispersion in the CRIT structure comprised of fiber.The results indicate the CRIT structure has potential applications in optical signal processing and optical communication.     

Efficient Integrated Graphene Photonics in the Visible and Near‐IR

Graphene photonics has emerged as a promising platform for providing desirable optical functionality. However, graphene's monolayer‐scale thickness fundamentally restricts the available light matter interaction, posing a critical design challenge for integrated devices, particularly in wavelength regimes where graphene plasmonics is untenable. While several plasmonic designs have been proposed to enhance graphene light interaction in these regimes, they suffer from substantial insertion loss due to metal absorption. Here we report a non‐resonant metamaterial‐based waveguide platform to overcome the design bottleneck associated with graphene device. Such metamaterial structure enables low insertion loss even though metal is being utilized. By examining waveguide dispersion characteristics via closed‐form analysis, it is demonstrated that the metamaterial approach can provide optimized optical field that overlaps with the graphene monolayer. This enables graphene‐based integrated components with superior optical performance. Specifically, the metamaterial‐assisted graphene modulator can provide 5‐fold improvement in extinction ratio compared to Si nanowire, while reducing insertion loss by one order magnitude compared to plasmonic structures. Such a waveguide configuration thus allows one to maximize the optical potential that graphene holds in the telecom and visible regimes.     

Survey of systems experiments demonstrating dispersion compensation technologies

Chromatic dispersion compensation is an integral part of WDM transmission system design. Compensator properties such as insertion loss, dispersion slope and effective mode area have a large impact on WDM system performance due to nonlinear optical propagation effects. Dispersion compensator imperfections, such as multi-path interference, group delay ripple, insertion loss ripple and limited per-channel compensation bandwidth, place additional limitations on the achievable transmission distance and capacity. In this paper, a survey of key WDM transmission system experiments is undertaken to 1) review the development of chromatic dispersion compensation technologies, 2) discuss the device characteristics that most impact system design for each technology, and 3) hopefully enable the reader to better evaluate compensator technologies for specific applications.     

Ka波段的反射型模拟电调移相器设计

为了能对射频信号进行连续相位调制,设计了Ka波段新型小型化的模拟电调移相器,该电路基于90°分支线电桥与并联结构变容二极管实现电路大范围移相,利用四分之一波长微带线实现电路匹配及阻抗变换,通过并联补偿电阻平衡其插入损耗波动,并对其进行了详细分析与探讨。仿真及实测结果表明:该移相器在29~31GHz频段范围内,可获得180°左右的相移量,插入损耗优于6.5dB,插入损耗波动在1dB内,相移误差小于10°。