Numerical analysis of amplification characteristics of ErxY2 − xSiO5

The gain characteristics of Er_xY_2 − xSiO₅ waveguide amplifiers have been investigated by solving rate equations and propagation equations. The gain at 1.53 μm as a function of waveguide length, Er³⁺ concentration and pump power is studied pumping at three different wavelengths of 654 nm, 980 nm and 1480 nm, respectively. The optimum Er³⁺ concentrations of 1 × 10²¹ cm^− 3-2 × 10²¹ cm^− 3 with the high gain are obtained for all three pump wavelengths. Pumping at 654 nm wavelength is shown to be the most efficient one due to weak cooperative upconversion. A maximum 16 dB gain at 1 mm waveguide length under a 30 mW pump with Er³⁺ concentration of 1 × 10²¹ cm^− 3 is demonstrated pumping at 654 nm wavelength.     

Semiconductor optical amplifiers at 2.0‐µm wavelength on silicon

A semiconductor optical amplifier at 2.0‐µm wavelength is reported. This device is heterogeneously integrated by directly bonding an InP‐based active region to a silicon substrate. It is therefore compatible with low‐cost and high‐volume fabrication infrastructures, and can be efficiently coupled to other active and passive devices in a photonic integrated circuit. On‐chip gain larger than 13 dB is demonstrated at 20 °C, with a 3‐dB bandwidth of ∼75 nm centered at 2.01 µm. No saturation of the gain is observed for an on‐chip input power up to 0 dBm, and on‐chip gain is observed for temperatures up to at least 50 °C. This technology paves the way to chip‐level applications for optical communication, industrial or medical monitoring, and non‐linear optics.

     

基于色散器件的波束形成网络中的色散限制

利用强度—频率混合调制模型研究了基于色散器件的波束形成网络中色散导致的相位误差的变化规律.基于相位误差的分析,得到了0.5 ps延时精度下系统对最大色散值的限制,并指出存在最优的频率调制系数使系统色散容限最大;随着强度调制系数增大,频率调制系数的最优值也增大.     

外调制激光器输出功率高精度控制技术研究

为了研究高速1550 nm微波光纤链路的高精度外调制特性,针对多量子阱分布反馈激光器的物理模型讨论了输出功率、阈值电流与温度的依赖关系,建立了相应的恒温恒功率控制电路,使激光器输出功率稳定在±0.005 dB以内,调制输出3 dB谱宽为0.5 nm,边模平坦,边模抑制比大于30 dB。另外设计了自动增益控制电路和附加相位调制电路,对外调制阶段的光功率进行控制。实验结果表明,采用1550 nm激光器及上述控制电路构成相应的外调制微波光纤链路系统,可有效地提高光发射模块输出光功率的稳定性,克服了直接调制带来的光谱展宽和消光比不稳定的缺点,实现了微波信号的高线性低失真传输。     

A novel highly efficient grating coupler with large filling factor used for optoelectronic integration

A novel highly efficient grating coupler with large filling factor and deep etching is proposed in silicon-on-insulator for near vertical coupling between the rib waveguide and optical fibre.The deep slots acting as high efficient scattering centres are analysed and optimized.As high as 60% coupling efficiency at telecom wavelength of 1550-nm and 3-dB bandwidth of 61 nm are predicted by simulation.A peak coupling efficiency of 42.1% at wavelength 1546-nm and 3-dB bandwidth of 37.6 nm are obtained experimentally.     

Light propagation in periodic photonic structures formed by photo-orientation and photo-polymerization of nematic liquid crystals

Propagation of linearly polarized light beams in a nematic liquid crystal cell with distinguished regions of different molecular orientation has been analyzed. Specifically, combination of the planar/homogenic and homeotropic alignment, forming thus spatially limited regions characterized by a different LC molecular orientation, has been tested, as achieved by means of the photo-orientation and photo-polymerization processes, independently. An influence of molecular orientation on the light beam propagation has been checked for different directions of the linear polarization. Thanks to the molecular reorientation induced by the low frequency external electric field and also to the reorientational nonlinearity taking place in NLCs, propagation direction of the light beam can be additionally controlled by the electric bias and/or optical power, respectively. Proposed structural solutions and techniques, related to the photo-orientation and photo-polymerization processes described in this communication, give rise to the novel LC geometries and structures. The latter act as promising candidates for new practical photonic applications as they are expected to be of a particular importance for integrated optic elements and devices.     

A bidirectional 60 GHz RoF system based on FWM in a semiconductor optical amplifier

In this study, a bidirectional 60 GHz RoF systems based on four-wave mixing (FWM) in semiconductor optical amplifier (SOA) is proposed. Two key techniques are included in such a scheme, namely, generation of 60 GHz modulating signals and distribution of 60 GHz local oscillator. The analytical model is theoretically analyzed and then confirmed by numerical simulations. Results of this study demonstrate that such a scheme can offer realistic solutions to support future mobile broad-band applications.     

Microwave Photonic Link with Carrier Suppression for Increased Dynamic Range

Theoretical analysis and experimental investigation of microwave photonic links with bias-shifted Mach-Zehnder modulators are presented. An optical amplifier is used to increase link gain and reduce noise figure. The combination of modulator bias shift away from quadrature and optical amplification reduces the link noise figure by more than 15 dB. For modulation frequencies from 2 to 18 GHz, the third-order limited spurious-free dynamic range (SFDR3) of these links is greater than 120 dB, normalized to a 1-Hz bandwidth. Conventional links based on Mach-Zehnder modulators are limited to SFDR3 values of approximately 110 dB, normalized to a 1-Hz bandwidth. This level of performance is achieved without electronic or optical linearization.     

MicroRNA快速检测系统的设计

为了实现MicroRNA的快速检测,设计了一种便携式MicroRNA快速检测仪.基于等温滚环扩增技术,采用光电检测方法,检测标志物受激发出的荧光光强,建立特征荧光分析检测系统.通过改变激发光强度、MicroRNA试剂浓度等参量,验证了该仪器可测量的MicroRNA的浓度范围为0.01~0.1μmol,可检测出的最低检出限为7个拷贝数,MicroRNA浓度与荧光信号强度之间为线性关系(R2=0.999 1).     

基于互逆光纤色散的微波光子雷达系统设计和实现

提出一种基于互逆光纤色散的微波光子雷达系统设计方案,既可以产生宽带线性调频信号,又可以实现线性调频信号的光域脉冲压缩.在发射端利用互逆色散光纤产生线性调频信号.在接收端,雷达回波信号通过马赫-曾德调制器调制到预啁啾的光信号上,然后经过色散光纤的进一步色散.最终在探测器端可以得到目标回波信号脉冲压缩后的结果.该方案无需脉冲压缩过程中数字化和离线处理,且具有脉冲压缩比的调谐作用.理论、数值仿真和实验证明了该设计方案能有效进行线性调频信号的光域脉冲压缩.实验产生了C波段下时宽1.2ns,带宽3.2GHz的线性调频信号,并通过互逆色散光纤将该信号压缩到了0.09ns,脉冲压缩比达13.3.