All-optical switching at ultralow light levels

We report an experimental demonstration of all-optical switching at ultralow light levels in coherently prepared Rb atoms. A signal light pulse is switched on and off by a control light pulse at different frequencies in a four-level atomic system based on multiphoton interferences. We observed a switching efficiency of 55% with the signal and control light pulses containing approximately 20 photons each, corresponding to a control energy density of approximately 10(-5) photons per atomic cross section lambda(2)/(2pi).     

Compact all-optical switch for WDM networks based on Raman effect in silicon nanowavegide

We propose an all-optical switching scheme based on Raman gain in a silicon nanowaveguide suitable for multichannel optical communication. Raman gain is used for amplification of a control pulse with a higher wavelength, which depletes the tuned channel signal. Separation between control and signal pulses should be equal to the Raman shift in silicon. By employing a 3 mm channel nanowaveguide, we demonstrate a channel attenuation of about 12 dB, while the suppression ratios for the first and second neighboring channels are about 1.6 dB and 1 dB, respectively. This scheme can be used as an all-optical switch in dense wavelength division multiplexing networks. Moreover, we demonstrate that the depleted channel can be retrieved by a control pulse with lower wavelength in which the pulse amplifies the channel in contrast to the prior situation.     

Controlling waveform of light pulse with light in optical fibers

We present our experimental demonstration of controlling waveform of a signal pulse by using two beams of continuous wave (CW) generated by stimulated Brillouin scattering (SBS) in optical fibers with different frequencies. Waveform of the signal pulse is modulated in an “all-optical” way according to total input power. This method is only suitable for light pulse with nanosecond width. We provide a new method for controlling light with light.     

Light‐switching‐light optical transistor based on metallic nanoparticle cross‐chains geometry incorporating Kerr nonlinearity

In this research work, we propose all‐optical transistor based on metallic nanoparticle cross‐chains geometry. The geometry of the proposed device consists of two silver nanoparticle chains arranged along the x‐ and z‐axis. The x‐chain contains a Kerr nonlinearity, the source beam is set at the left side of the later, while the control beam is located at the top side of the z‐chain. The control beam can turn ON and OFF the light transmission of an incoming light. We report a theoretical model of a very small all‐optical transistor proof‐of‐conceptmade of optical ‘light switching light'concept. We show that the transmission efficiency strongly depends on the control beam and polarization of the incoming light. We investigate the influence of a perfect reflector and reflecting substrate on the transmission of the optical signal when the control beam is turned ON and OFF. These new findings make our unique design a potential candidate for future highly‐integrated optical information processing chips.     

Optical bistability in low-dimensional semiconductor heterostructures under cw pump laser and infrared pulse signals

We have investigated theoretically the optical bistability (OB) and optical multistability in quantum-well (QW) semiconductor heterostructures. The effect of a cw pump laser field and a control infrared pulse signal on OB is discussed. It is found that the OB threshold can be controlled by varying the strength of applied fields. It is also shown that OB can be switched to optical multistability or vice versa just using an appropriate relative phase of applied fields. This investigation may open up some new possibilities for applications in all-optical switching in quantum-well structures.     

研制超宽带全光取样示波器设备

全光取样示波器是研究与开发超高速光通信系统和光子交换网络的关键性测试仪器设备. 本文简介了我们自行设计和研制出的超宽带全光取样示波器设备的实验样机系统, 并报道了我们已取得的初步实验结果. 采用自主研发的高稳定性被动锁模飞秒光纤激光器作为该光学示波器的光脉冲取样源, 我们通过利用高度非线性光纤中的四波混频效应, 成功地实现了对脉宽为1.8ps、重复频率分别为10GHz和40GHz的光脉冲信号的全光取样. 然后通过数字信号处理和计算机图形处理, 得到了再现后的超短光脉冲信号波形, 并测出了其脉冲宽度值为2.3ps. 借助于该光学取样示波器实验样机, 我们还成功地完成了对脉宽为1.8ps、经过伪随机数据序列调制后的10Gbit/s和40Gbit/s光数据信号眼图的精确测量. 这是我国首次报道有关超宽带全光取样示波器设备的实际研制工作及其相应的实验测试结果. 所得到的有关超短光脉冲信号波形的测试结果也与用70GHz宽带电子示波器和超快光电探测器组成的常规光电测量系统所获得的结果进行了比较, 清楚地表明了我们研制出的全光取样示波器实验样机比后者具有更高的时间分辨率和更大的测量带宽.     

All-Optical WDM Buffer System Realized by NOLM and Feedback Loop Structure

We propose an all-optical WDM buffer for optical packet switching system, which consists of NOLM and feedback loop. The proposed structure provides more than 40 turn buffering and nice output of buffered data when selected by control signal.     

级联二阶非线性铌酸锂全光开关的研制

以基于准位相匹配和频与差频级联二阶非线性[X^(2)：X^(2)]基础上的全光开关的理论分析作指导,进行了周期极化铌酸锂晶体(PPLN)和退火质子交换光波导(APE)的实验制备,利用所研制的PPLN-APE器件,以自行研制的工作波长为1．54μm的被动调Q掺钴铝酸镁激光器作为控制光源,以工作波长为1．5μm的连续二极管激光器为信号光源进行了级联二阶非线性全光开关实验。当控制光峰值功率为3kw,信号光功率为1mW时,实现13％的开关效率,分析了进一步提高全光开关性能的途径。     

Nonlinear All-Optical Switching Device by Using the Spatial Soliton Collision

We propose a new nonlinear all-optical switching device by using the spatial solitons collision. This is 1 × N switching device controlled by two control beams. The numerical results show that this device could really function as a 1 × N all-optical switching device. This device is a potential key component in the application of optical signal processing and optical computing systems.     

Dual-channel all-optical switching with tunable frequency in a five-level double-ladder atomic system

A scheme of five-level double-ladder-type atomic system is proposed with the aim of implementing dual-channel all-optical switching. Two transitions in the five-level atomic medium independently interact with the two orthogonally (circularly) polarized components from a weak linearly-polarized probe beam, while two other atomic transitions are coherently driven by a control beam and a switching signal beam. We demonstrate that the switching on/off of two orthogonally polarized beams at different frequencies can be achieved by adjusting the magnitude of the external magnetic field, which expands the frequency range of an optical signal switching operation and may improve its practicability.     

Demonstration of an all-optical switching operation using an optical fiber grating coupler

An optical fiber grating coupler (FGC) is a fused optical fiber coupler with a tapered region in which refractive index-modulated gratings are written. In the FGC, the light with specific wavelength satisfying the Bragg condition of the grating can be dropped to one output port and other lights are transmitted to another output port when lights with various wavelengths are launched into the input port. The FGC can operate as an all-optical switch by controlling the Bragg wavelength of the grating using a third order nonlinear optical effect caused by a control light that are launched with a signal light. In this paper, an all-optical switching operation due to a third order nonlinear optical effect in an FGC is first demonstrated for a signal light with 1.55 μm-wavelength to be changed from one port of the FGC to another one by the 720 W peak of a control light from a Nd:YAG laser with 1.06 μm-wavelength. The switching efficiency obtained was 7%. It was clarified that a longer pulse length of the control light compared to the grating length is required to obtain a large Bragg wavelength shift for the switching. It was also clarified that the Bragg wavelength shift is caused by a third order nonlinear effect and a photothermal effect. A contribution of the photothermal effect was estimated. We also estimated the switching efficiency for pump power in the FGC switch.     

Generation of 40-GHz control signals from flag pulses for switching all-optical gates for use with optical packets

We demonstrate an all-optical circuit capable of generating 40-GHz control signals from flag pulses that can be used to define the switching state of all-optical gates for use with optical packets. The circuit comprises a Fabry-Perot filter and a semiconductor optical amplifier, and with a single pulse it can generate 12 control pulses with 0.64-dB amplitude modulation. With two and three flag pulses the number of control pulses becomes 36 and 54, respectively.     

Asymmetric Nonlinear Optical Loop Mirror for All Optical Clock Extraction in Self-clocked Optical Transparent OTDM Network

１ＩｎｔｒｏｄｕｃｔｉｏｎＡｓａｅｆｅｃｔｉｖｅｗａｙｔｏｔａｋｅｆｕｌａｄｖａｎｔａｇｅｓｏｆｔｈｅｂａｎｄｗｉｄｔｈｏｆｔｈｅｆｉｂｅｒ,ｏｐｔｉｃａｌｔｉｍｅｄｉｖｉｓｉｏｎｍｕｌｔｉｐｌｅｘｉｎｇ（ＯＴＤＭ）ｔｅｃｈｎｏｌｏｇｙｈａｓｂｅｎｗ...     

相移干涉计量中相移器的原路相干相位检测标定

A new all-optical clock extraction scheme based on an asymmetric nonlinear optical loop mirror (NOLM) is proposed and demonstrated experimentally. The proposed scheme can operate at a relatively low switching power (only 0.3 Pπ is required for the clock pulse, where Pπ means the required switching power for the maximum switching in the asymmetric NOLM) and a relatively low input clock to data ratio (2～2.5). The proposed scheme is promising for clock extraction in the future ultrahigh-speed self-clocked OTDM network.     

利用腔内四能级原子相干效应实现全光学信号存储

在光学腔与四能级原子组成的非线性光学双稳系统中，利用调谐于不同能级附近的控制信号光脉冲可以使光学腔模产生“IT”或“负”的非线性相移，从而实现了光学双稳迟滞曲线的受控移动及双稳“高态”与“低态”之间的可控跃变，基于上述效应，完成了光学信号的全光存储与腔输出状态的低功率控制开关．这一结果为全光及量子信息处理提供了新的可供利用的物理机制．     

Nonlinear All-Optical Switching Device by Using the Spatial Soliton Collision

We propose a new nonlinear all-optical switching device by using the spatial solitons collision. This is 1 × N switching device controlled by two control beams. The numerical results show that this device could really function as a 1 × N all-optical switching device. This device is a potential key component in the application of optical signal processing and optical computing systems.     

All-optical sampling exploiting nonlinear polarization rotation in a single semiconductor optical amplifier

An all-optical sampling scheme using a single semiconductor optical amplifier is proposed for analog signal processing. The analog optical signal is sampled by the probe pulse train through the nonlinear polarization rotation arising in the semiconductor optical amplifier. Conversion efficiency and total harmonic distortion are presented to evaluate the sampling linearity. In the experiment, 40 GSa/s all-optical sampling for 2.5 GHz analog optical signal is successfully demonstrated with commercially available fiber-pigtailed components. The results show that the fundamental conversion efficiency and the total harmonic distortion are 1.35 and 2.01% at the operating power of 5 mW, respectively. The proposed all-optical sampling requires only one semiconductor optical amplifier and has low power consumption, which is simple and has potential for photonic integration.     

Ultrafast all-optical signal processing with Symmetric Mach–Zehnder type all-optical switches

We present Symmetric Mach–Zehnder (SMZ) type all-optical switches: an SMZ all-optical switch, a polarization-discriminating SMZ (PD-SMZ) all-optical switch, and a delayed interference signal wavelength converter (DISC). These switches are capable of ultrafast, low control power, and low chirp switching, which is not restricted by slow relaxation of highly efficient nonlinearities. High repetition operation unrestricted by slow relaxation is also possible for these switches. This is because of a push–pull modulation scheme or sometimes called a differential phase modulation scheme. These three devices are similar, but different in some important aspects, thus a comparison is made among the three. Then semiconductor optical amplifiers (SOAs) are discussed as a nonlinear phase shifter for these devices. Then, ultrafast all-optical signal processing using SOA based SMZs is demonstrated. Error-free demultiplexing from 168 to 10.5 Gbit/s is presented, in which a hybrid-integrated SMZ (HI-SMZ) is used as a demultiplexer. In pulse regeneration experiment, the signal pulses at 84 Gbit/s are regenerated by the PD-SMZ and the regenerated pulses are demultiplexed to 10.5 Gbit/s by the HI-SMZ to verify error-free operation. The retiming capability of this scheme is quantitatively demonstrated. Also presented is error-free all-optical wavelength conversion at 168 Gbit/s using the DISC. These results represent the fastest error-free operations reported to date in each category.     

Experimental Study on Optical Limiting and Transient All-optical Switching Properties of a Cubanelike Transition-metal Cluster Compound (n-Bu4N)3[MoAg3BrI3S4]

１ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｒｅｃｅｎｔｙｅａｒｓ,ｔｈｅｐｏｔｅｎｔｉａｌｏｆｒｅｖｅｒｓｅｓａｔｕｒａｂｌｅａｂｓｏｒｐｔｉｏｎ（ＲＳＡ）ｍａｔｅｒｉａｌｓｉｎｏｐｔｉｃａｌｌｉｍｉｔｉｎｇａｎｄｏｐｔｉｃａｌｓｗｉｔｃｈｉｎｇｈａｖｅｇｒａｄ...     

光梯度力驱动的纳米硅基光开关

通过一道光改变另一道光的传输路线是光子集成网络中重要而长远的目标, 然而, 由于硅材料的光学非线性较弱, 在硅材料上实现开关的全光控制难以实现. 因此本文提出了一种由光梯度力驱动的纳米硅基光开关, 实现了硅基光开关的全光控制. 该光开关由一个部分悬空的微环谐振器和一个交叉波导结构构成, 当通入一道控制光时, 悬空的微环谐振器在光梯度力的作用下发生弯曲, 微环谐振器的谐振波长随之发生变化, 从而实现光信号的传输路线发生改变. 该光开关利用纳米光子制造技术在标准绝缘体上硅晶圆上制造, 实验数据得出其最小消光比为10.67 dB, 最大串扰为 -11.01 dB, 开关时间分别为180 ns和170 ns. 该光开关具有尺寸小, 响应速度快, 低损耗和可拓展等优点, 在片上集成光路、高速信号处理以及下一代光纤通信网络中具有潜在应用.