光控相控阵波束接收网络

文中提出了一种基于光纤色散真时延技术的光控相控阵雷达多波束接收网络。该网络制作原理是根据光纤的色散特性,主要由密集波分复用器(DWDM)和光纤延时模块构成。DWDM 实现对多通道光合成,多个光开关和光纤延时环组成的光纤延时模块实现对合成的多路光载波进行延时量调节,从而实现波束扫描。依据原理方案,研制了一套16通道光接收、双波束形成网络,实现从-40°到+45°的16个不同波束指向扫描,切换速度≤30us。暗室测试证明了其波束形成能力。     

光子晶体光纤参量放大的理论模拟

光子晶体光纤具有高非线性系数和非常灵活的色散特性，通过调节光子晶体光纤的结构参量，可在具有高非线性系数的同时对光子晶体光纤的零色散波长(λ0)进行调节。利用光子晶体光纤的这些特性可实现在所需波长上的高效率的参量放大。本文采用厄密-高斯函数展开的方法，计算了六角形光子晶体光纤(HF)的零色散波长，发现当气孔间距在1．1μm和2．6μm之间时，光子晶体光纤的零色散波长在1．55μm附近，并给出了零色散波长时气孔间距和气孔大小的关系曲线。对光子晶体光纤中的参量放大(OPA)进行了理论模拟，计算表明在20m光子晶体光纤中，当峰值功率为10W时，参量放大的增益可达60dB，或可获得300nm增益带宽。     

利用参量放大效应测量光纤的非线性系数和色散参数

通过对理想条件下得出的光纤参量放大增益解析解和相位匹配关系表达式进行修正,得出在光纤有损耗 时,小信号峰值增益和光纤非线性系数成正比以及光纤色散参数和峰值增益波长与抽运光波长的差成反比两个近 似表达式。以此为基础提出:只要在直流抽运光作用下测出小信号峰值增益以及增益峰值波长与抽运波长之差, 然后通过简单的代数运算就可以得出光纤的非线性系数和色散参数。实验中,分别用两个不同波长的抽运光,对 一卷长度为1450m的高非线性色散平坦光纤(HNLF)的非线性系数和色散参数进行了测量。测得非线性系数为 γ=11.8W-1·km-1,色散斜率在1550nm附近为S=0.0157ps/(nm2·km)。其中,色散斜率测量值和商家给定的 值之间误差不超过5%。对在测量中抽运光和信号光之间由于拉曼放大作用所带来的增益谱不对称性进行了讨论。     

硅基光子集成宽带大色散延时芯片（特邀）

集成、宽带、大色散延时的器件在微波光子滤波、真延时相控阵天线等领域有着重要的应用,可以有效地降低系统尺寸和功耗。文中提出并实现了一种基于硅基光子集成的宽带大色散延时芯片,通过采用超低损耗波导结构和侧壁法向量调制结构实现了片上集成大色散波导光栅,色散值超过250 ps/nm, 最大群延时达到2440 ps,带宽大于9.4 nm,该芯片有望用于微波光子学、高速光纤通信系统等领域。     

色散平坦光子晶体光纤中实现光波变换的研究

基于四波混频(FWM)效应,在色散平坦光于品体光纤(PCF)中实现了全光波长变换.采用长度为30 m、具有小的反常色散值的高非线性色散平坦PCF对10 Gbit/s的信号进行了波长变换,当平均泵浦功率为26dBm时,在20 nm转换带宽内得到了-19.5 dB的转换效率;用具有小的正常色散值的高非线性色散平坦PCF替代原光纤,进行了实验与理论比较.研究结果表明:利用两种不同的光纤得到了儿乎相同的转换效率和转换带宽.     

可编程控制波长调谐的环形掺铒光纤激光器

提出了一种新型的可调谐光纤激光器,器件采用介质薄膜干涉滤波器进行波长可编程调谐,调谐范围超过38 nm(1 526.5～1 564.6 nm),中心波长可精确调谐到C波段指定的ITU-T波长栅格的标准中心波长处,3 dB带宽小于0.08 nm,25 dB带宽小于0.22 nm,波长稳定性优于0.01 nm,边模抑制比大于60 dB,最大输出光功率35.6 mW,功率稳定性优于±0.02 dB,阈值泵浦功率和斜率效率分别为5.8 mW和36.6%.     

基于光子晶体光纤的宽带相控阵雷达多波束形成技术

提出了基于光子晶体光纤（PCF）的光学多波束形成网络,利用光子晶体光纤的高色散值和色散平坦特性实现了光学真延时（TTD）,并采用光波分复用技术形成了多个射频波束的独立控制和扫描。仿真结果表明,通过改变工作波长能够有效实现射频信号的相对延时,且延时差与理论计算值相符。     

相控阵雷达天线延时技术的发展

介绍了相控阵雷达天线在大扫描角及大瞬时带宽应用场景下延时补偿技术的发展概况。对天线阵列的波束色散现象以及延时补偿技术对天线方向图的影响进行了分析,并介绍了国内外的一些延时方案。依据延时实现架构,将其分为微波延时、表面声波延时、光延时以及数字延时四类。重点对微波延时的几种不同类型的实现形式进行了描述,并根据微波延时线实现载体的不同,分为GaAs 芯片、射频电缆、印制板和微同轴四种。另外,针对延时拓扑电路进行理论推导分析,说明单延时路径在电路设计上的优势,并分析了基态链路对延时路径的幅度、相位补偿和介质材料对延时量的误差引入。对相控阵雷达天线在大扫描角及大瞬时带宽应用场景下的延时补偿技术研究有一定参考价值。     

利用正常色散微结构光纤产生平坦的超连续谱

利用1.7 ps、中心波长为1565 nm和重复率为10 GHz光脉冲入射到80 m具有小正常色散的色散平坦高非线性微结构光纤(HNL-MF)中,在通信波段获得平坦展宽超过100 nm的超连续谱.除了在泵浦波长附近几nm波长范围内具有小的谱峰外,超连续谱在1 512～1 612 nm内具有±3 dB的平坦度.同时研究了不同泵浦波长情况下超连续谱产生的情形,由于不同泵浦波长处光纤的色散斜率不同,因此对超连续谱对称性产生一定的影响,色散斜率越小,产生的谱的对称性也越好.     

基于光子晶体光纤和飞秒激光源的近红外波段宽带孤子和可见区高效色散波产生的实验

将钛宝石激光器产生的飞秒激光脉冲泵浦实验室自制的高非线性双折射光子晶体光纤,脉冲的中心波长为820 nm,位于光子晶体光纤的接近于零色散的反常色散区.实验结果表明:随着泵浦功率的增加,一阶孤子的中心波长发生了红移,同时产生的色散波的中心波长则发生蓝移进入可见光区.当泵浦功率达到0.45 W时,色散波与残余泵浦的输出功率比为42.67,色散波的带宽达到81 nm,而处于近红外波段的红移孤子带宽可达231 nm.利用高非线性光子晶体光纤产生近红外波段宽带孤子和可见区高效色敬波的实验对飞秒激光频率转换和光谱展宽具有很好的借鉴意义.     

波长可切换窄线宽单频掺镱光纤激光器（特邀）

基于光纤环形激光器,设计出由三端口环形器、偏振控制器、未泵浦保偏掺镱光纤和光纤布拉格光栅组成的滤波器件作为高精度滤波器对谐振腔内的模式个数进行抑制,通过调谐偏振控制器,在保偏掺镱光纤内形成的梳状光谱和动态光栅,实现了窄线宽、单、双波长可切换单频掺镱光纤激光器。单波长运行时,在1064.37 nm处测得激光器输出线宽346 Hz,光信噪比大于50 dB,30 min内该激光器波长及功率的不稳定性均在0.01 nm和0.2 dB范围内。通过调节偏振控制器,单波长和双波长可以实现互相切换,双波长分别位于1064.156 nm和1065.236 nm。该技术为超窄线宽激光器的双波长输出提供了新的途径。     

Wavelength-graded horizontal cavity laser array with postgrowthadjustment of wavelength

Wavelength-graded emission from a visible red GaInP-AlGaInP laser diode array has been achieved with the contradirectional surface-mode coupling technique. The wavelength control is attained by postgrowth adjustment of the thickness of the surface waveguide. The horizontal cavity lasers show both edge and surface emission (beam divergence 0.12°). The thermal red-shift of the wavelength is 0.028±0.002 nm/K. They show single-mode emission with a typical spectral linewidth of 0.09 nm and a sidemode suppression ratio up to 29 dB. The wavelength spacing between the individual lasers is 0.76±0.08 nm yielding a total range across the array of 5.4 nm (from 681.5 to 686.9 nm)     

1 015~1 046 nm可调谐飞秒掺镱光纤激光器

近年来,超快掺镱锁模光纤激光器由于其转换效率高、操作方便、免维护、尺寸紧凑等优点,被广泛应用于工业加工、医疗外科、多光子成像等领域。在激光器中补偿群速度色散是获得皮秒甚至飞秒脉冲的有效方法。通过利用光栅对与光谱滤波器,实现了对激光波长、腔内色散和光谱宽度的灵活调节。该激光器能输出稳定的锁模脉冲,对应的基本重复频率为19.41 MHz。在+ 0.0127 ps2色散时中心波长1015~1037 nm可调;在+0.007 ps2色散时中心波长1015~1045 nm可调以及在?0.0127 ps2色散时中心波长1020~1046 nm可调。同时,当净腔色散从反常色散到近零色散变化时,光谱带宽可从1.40 nm调到19.38 nm,对应的压缩后脉冲宽度可从1.03 ps调至175.9 fs。该方案具备连续调整激光器状态的能力,有望用于高功率大能量飞秒激光前端,可以满足对激光器有多种谱宽及波长的应用需求。     

Low-threshold four-wavelength DFB laser array for multigigabit/s high-density WDM systems applications

A high-speed four-wavelength distributed-feedback (DFB) laser array with narrow wavelength spacings ( approximately 3 nm), very low-threshold currents ( approximately 5 mA), and all wavelengths, and operating (1540-1550 nm) within the erbium-doped fiber amplifier bandwidth has been fabricated. Electrical crosstalk of less than -25 dB up to 5 GHz was measured and a small wavelength drift caused by heating effects was observed for adjacent lasers. However, neither the electrical crosstalk nor the thermal effect causes any sensitivity penalties in a high-speed wavelength-division multiplexing transmission system.<>     

Continuous True-Time-Delay System Employing a Novel Tunable Chirped Fiber Grating Delay Line and a Sampled Grating Based Multiwavelength Fiber Laser

A photonics true-time-delay system for phased array antenna beam steering employing a novel tunable chirped fiber grating delay line and a multi-wavelength erbium-doped fiber ring laser source based on a sampled grating filter is proposed. The tunable chirped fiber grating, which act as a continuous time-delay element, is achieved by bending a uniform fiber Bragg grating bonded at a slant onto the lateral surface of a simply supported beam. This technique allows the dynamic control of the chirp rate and spectral width of the grating without center wavelength shift. By adjusting the chirp rate of the fiber grating via bend strain, this kind of tunable chirped fiber grating could achieve very low and adjustable delay times, therefore provides higher angle resolution for scanning microwave beam, even the wavelengths of laser source are fixed and un-tunable. The true-time-delay system using proposed tunable chirped fiber grating delay element and sampled grating based laser source is constructed and demonstrated experimentally.     

利用非线性偏振旋转效应的可调谐多波长光纤激光器

提出了一种基于非线性偏振旋转(NPR)效应的可调谐多波长掺铒光纤(EDF)激光器,非线性偏振旋转诱导的强度相关非均匀损耗有效地抑制了均匀加宽增益介质掺铒光纤中的模式竞争,使光纤激光器在室温下产生稳定的多波长输出。其中利用保偏光纤和偏振相关隔离器组成的等效Lyot 双折射光纤滤波器作为波长选择器件,该滤波器可以通过选择合适的双折射光纤长度改变波长间隔,调节偏振控制器改变偏振态实现对波长的精密调谐。实验采用10 m长的保偏光纤(PMF),得到了波长间隔为0.35 nm、最多17个波长的稳定激光输出,并且实现了输出波长在4 nm范围内的连续可调谐。分别采用10:90、30:70和50:50的输出耦合器,激光信号分别从10%、30%和50%的端口输出,得到了最多17、14和13个波长的输出,其波长功率浮动分别为13 dB、10 dB和7 dB,另外,其最大输出功率分别为-7 dBm、-3 dBm和0 dBm。实验结果表明,输出耦合器输出端比例越大,输出波长就越少,各波长激光输出功率越平坦,且输出功率越高。     

Monolithic integration of thin film μ-heater array with 4-channel WDM transmitter

We integrated a μ-heater array with a multi-wavelength laser array for accurate control of the channel spacing. A μ-heater array was formed on a 4-channel laser array with asymmetric sampled gratings. The lasers showed threshold current of 9-13 mA and slope efficiency of around 0.21 W/A. High side mode suppression ratio over 44 dB was observed as well. With the μ-heaters, all the laser wavelengths were precisely controlled simultaneously. The laser wavelength was red shifted with the μ-heater and the tuning efficiency was 3.3 nm/W. However, thermal crosstalk between neighboring channels was observed and it was measured to be 1.1 nm/W.     

室温稳定多波长光纤激光器技术的研究新进展

室温稳定的多波长光纤激光器( MWFL)中最关键的技术是如何有效抑制掺杂光纤的均匀展宽效应。综述了国际上近年来提出的实现室温稳定多波长光纤激射的主要技术。介绍了近几年我们在该领域的一些创新性研究工作:提出了多种基于多谐振峰的光纤布拉格光栅(FBG) ,如多模光纤布拉格光栅、保偏光纤布拉格光栅、取样光纤布拉格光栅等的可开关多波长光纤激光器的新方法和新结构,实现了多种波长间隔小于2 nm,室温工作稳定性好、波长及波长间隔可调的可开关多波长光纤激光器;提出了基于非线性光纤环镜( NOLM)和非线性偏振旋转(NPR)效应的两种多波长掺铒光纤激光器(EDFL)实现技术,实现了室温稳定、功率谱分布平坦的宽带多波长激光输出,3 dB带宽内的波长个数可达50个,每个波长的功率波动在2 h内小于0 .1 dB。     

Monolithic multiple wavelength surface emitting laser arrays

A two-dimensional (2-D) surface emitting laser array emitting 140 unique, nonredundant, uniformly separated, single-mode wavelengths in the 980-nm regime is described. The wavelength separation between neighboring lasers is as small as 0.3 nm. A large total wavelength span of 43 nm was obtained without compromising the performance of the lasers. All 140 lasers have nearly the same threshold currents, voltages, and resistances. The techniques used are generic and can be readily extended to both longer and shorter wavelength lasers. The authors also report the first wavelength division multiplexing system experiment using part of this laser array. A BER (bit-error ratio) of 10 ^-9 at 155 Mb/s was obtained with simultaneous operation of four lasers at a wavelength separation of 1.5 nm. Negligible optical and electrical crosstalk was observed between the lasers     

Low-threshold 1.5 mu m DFB laser grown by GSMBE

GaInAsP 1.5 mu m DFB lasers with a low threshold current (17 mA) have been grown by gas source molecular beam epitaxy (GSMBE) in a two-step epitaxial process. The lasers exhibit single-mode emission for emitted power in excess of 10 mW with side mode suppression ratio of 40 dB and spectral linewidth of 15 MHz. In addition the dispersion of the lasing wavelength has been found to be as low as 1.7 nm.<>