Controllable four-wave mixing response in a dual-cavity hybrid optomechanical system

We systematically investigate the four-wave mixing(FWM) spectrum in a dual-cavity hybrid optomechanical system,which is made up of one optical cavity with an ensemble of two-level atoms and another with a mechanical oscillator. In this work, we propose that the hybrid dual-cavity optomechanical system can be employed as a highly sensitive mass sensor due to the fact that the FWM spectrum generated in this system has a narrow spectral width and the intensity of the FWM can be easily tuned by controlling the coupling strength(cavity–cavity, atom–cavity). More fascinatingly, the dual-cavity hybrid optomechanical system can also be used as an all-optical switch in view of the easy on/off control of FWM signals by adjusting the atom-pump detuning to be positive or negative. The proposed schemes have great potential applications in quantum information processing and highly sensitive detection.     

Dynamical switching and memory via incoherent pump assisted optical bistability

We analyze the dynamical behavior of all-optical switching and memory based on tunable optical bistability in a three-level Λ-type atomic system driven by a probe field circulating in an optical ring cavity, a coherent coupling field and an incoherent pump field outside cavity. Owing to the incoherent pump process, the absorption and Kerr nonlinearity near the atomic resonance change dramatically as a result of varied population distribution and atomic coherence, and then the switch-up and switch-down thresholds, as well as the width (or area) of bistable curve, can be manipulated effectively. By tuning the intensity of either coherent coupling field or incoherent pump field, we can make the system output flip between the lower and upper branches of different bistable hysteresis loops while the cavity input keeps to a constant value. Accordingly, all-optical switching and memory can be implemented via dynamical control of the bistable behavior under the assistance of incoherent pump. The proposed scheme can find potential applications in all-optical communication and computation.     

Tunable interaction-free all-optical switching in a five-level atom-cavity system

A scheme is proposed for tunable all-optical switching based on the double-dark states in a five-level atom-cavity system. In the scheme, the output signal light of the reflection and the transmission channels can be switched on or off by manipulating the control field. When the control light is coupled to the atom-cavity system, the input signal light is reflected by the cavity. Thus, there is no direct coupling between the control light and the signal light. Furthermore, the position of the double-dark states can be changed by adjusting the coherent field, and,thus, the switching in our scheme is tunable. By presenting the numerical calculations of the switching efficiency,we show that this type of the interaction-free all-optical switching can be realized with high switching efficiency.     

Low-light-level all-optical switching

We propose an all-optical switch that utilizes the technique of storage and retrieval of light pulses. A single photon (probe pulse) switched by another (switching pulse) is feasible, and the on-off ratio can be as large as 10 dB. We have experimentally demonstrated that the energy of the retrieved probe pulse is reduced to about 10% because of the presence of a switching pulse with an energy per unit area of one photon per lambda(2)/(2pi). The achieved result does not depend on the coupling intensity, the atomic optical density, or the width and shape of the switching pulse.     

基于半导体光纤环形腔激光器的新型全光AND门和NOR门

提出了一种新型的基于半导体光纤环形腔激光器(SFRL)中同时发生的四波混频效应和交叉增益调制效应同时实现全光AND门和NOR门方案，并建立了这种全光逻辑门完整的宽带理论模型.通过数值模拟的方法，研究了输入信号光峰值功率及SFRL中两个耦合器的耦合比对这种全光逻辑门输出特性的影响. 关键词： 半导体光纤环形腔激光器 全光逻辑门 四波混频 交叉增益调制     

基于自相位调制和交叉相位调制的全光开关特性研究

提出一种优化含有掺铒光纤放大器的非线性Sagnac干涉仪全光开关的新方法,建立了基于自相位调制和交叉相位调制两种解析模型,讨论了掺铒光纤放大器的小信号增益和饱和输出功率对开关性能的影响.分析表明掺铒光纤放大器的性能参量对开关所需要的Sagnac环中光子晶体光纤长度产生限制.当采用相同长度的光子晶体光纤时,基于交叉相位调制方式的全光开关与基于自相位调制方式的全光开关相比能够显著降低开关功率.采用分布傅里叶法数值求解非线性薛定谔方程,优化了开关结构,讨论了重复频率为40 GHz脉宽为5 ps的高斯型信号脉冲在开关时沿Sagnac环的传输特性.模拟结果表明,通过合理选择高非线性光子晶体光纤长度和掺铒光纤放大器的性能参量能够实现超低开关功率（＜1 mW）的开关操作.     

Proposal for all-optical controllable switch using dipole induced transparency (DIT)

We propose a novel all-optical controllable switch using photonic crystal cavity. For doing this work, the dipole induced transparency phenomenon realized through interaction of light with multilevel nanocrystals is used. Multilevel nanocrystals are doped to photonic crystal rods. Using the proposed structure and applying the control field, the absorbing medium converts to transparent one and switching operation is obtained. Analytical relation for evaluation of the proposed device considering quantum optical effects is presented and studied by investigation of effects of parameters on switching characteristics. We show that high quality all-optical switching operation can be obtained.     

All-optical subpicosecond magnetic switching in NiO(001)

Combining optical control theory with ab initio quantum chemistry and electronic crystal field theory we explore the laser induced femtosecond spin dynamics. We propose a scenario for ultrafast all-optical magnetic switching that results from the combination of spin-orbit coupling with appropriately shaped short laser pulses. We find that the application of the theory to the multiplet states within the gap of NiO(001) predicts for the first time the possibility of all-optical spin switching within 100 fs. The switching can be observed using any of the multiplets as the intermediate state.     

拉曼放大辅助波长可选择的全光开关

使用3-dB耦合器组成M-Z干涉仪,在M-Z干涉仪的一臂加入高非线性光纤(HNLF)组成的反向拉曼放大器,改变放大器的泵浦波长及强度,可实现波长可选择的全光开关。其功能可用于波分复用(WDM)系统,对不同波长的上、下载选择有很大的应用意义。理论分析了实现这一功能的可行性和参数选择,考虑拉曼放大并伴有交叉相位调制(XPM)引起信号光的相移,推导分析了在引入放大的同时又引入相移,怎样选择放大和相位匹配问题,来实现波长可选择的光开关的要求。     

Observation of switching phenomena in a nonether polyphenylquinoxaline planar waveguide with two-wavelength nonlinear prism coupling

We present research on nonether polyphenylquinoxaline film waveguides, and a scheme for an all-optical switching operation of waveguides is suggested. We use the m-line spectroscopy technique to characterize the guiding modes in the waveguide, and the switching phenomenon is observed with two-wavelength nonlinear prism coupling. The measured response time of the switching signal is less than 10(-9) s.     

Optimized all-optical amplitude reshaping by exploiting nonlinear phase shift in fiber for degenerated FWM

We describe a novel performance optimization method for all-optical amplitude reshaping via degenerated four-wave mixing(FWM) in highly nonlinear optical fiber.The proposed optimization method is achieved by judiciously configuring the FWM operational condition and exploiting the nonlinear phase shift induced by self-and cross-phase modulations to properly influence the FWM conversion efficiency.Through the proposed scheme,fully functional and prevailing reshaping performance,including significant amplitude jitter suppression and extinction ratio improvement,is obtained within a single FWM stage.Results of the present theoretical calculation and numerical simulation verify the feasibility and advantages of the proposed scheme.     

Manipulation of tunneling induced transparency windows and optical switching features in fivefold quantum dot molecules

Transient and steady-state behavior of the probe absorption in a multiple quantum dot (QD) molecule composed of five quantum dots molecules (with a center dot and four satellite dots) is explored with application in all-optical switching. We find that the absorption spectra of the light pulse can be efficiently modified via the effect of inter-dot tunnel couplings of QDs and incoherent pumping field. Results show that depending on the values of system parameters, at least one and at most four tunneling induced transparency (TIT) windows can be established in the multiple QD medium. We then investigate the dynamical behavior of the probe absorption-amplification as well as the optical switching in pulsed regime. By adjusting the incoherent pumping rate, the required switching time for changing the gain to the absorption or vice versa is then estimated approximately to be 20.7 nanosecond (ns), that is an appropriate time for such a QDM-based switch.     

Integrated CMOS system and thermally actuated optical switch for wavelength modulation/lock in communication network

The advancement of communication technology and growth of internet traffic have continuously driven the fast evolution of networks. Compared to the traditional optoelectronic switch, all-optical switch provides high throughput, rich routing functionalities, and excellent flexibility for rapid signal exchange in fiber optical network. Among various all-optical switches, thermal actuated ring switch provides the advantages of high accuracy, easy actuation, and reasonable switching speed. However, when scale up, thermal ring switch may encounter issues related to fabrication error, non-accurate wavelength response, and large terminal numbers in the control circuit. In this research, we propose the employment of an integrated CMOS control circuit to compensate the fabrication error and tune as well as lock the wavelength in a thermal-actuated ring-type optical switch through a frequency modulation scheme. Additional functionalities can also be added in this circuit by tailoring externally the roundtrip loss or coupling constants of the ring. The design concept can be easily scaled up for large array optical switch system without much change in the terminal numbers thanks to the three-dimensional hierarchy of control circuit design, which effectively reduces the terminal numbers into the cubic root of the total control unit numbers. The integrated circuit has been designed, simulated, as well as fabricated, and demonstrated a decent performance with free spectral range (FSR) equal to 1.5 nm at 1534 nm and very accurate wavelength modulation to 0.3 nm within 0.01 nm fluctuation for thermal actuated ring type optical switch.     

Optical Switching in Silicon Nanowaveguide Ring Resonators Based on Kerr Effect and TPA Effect

We analyze theoretically the 1 × 2 low-power all-optical switching in silicon nanowaveguide ring resonators （RR） based on the Kerr effect and two-photon absorption （TPA）, and give a comparison between both the all-optical switches. The calculation shows that the switching power of the TPA-RR switch is 3 orders smaller than that of the Kerr-RR switch. The switching time for both the switches is about 100ps.     

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.     

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.     

一种新型全光开关

提出了一种用指数型变耦合系数定向耦合器同高斯型变耦合系数定向耦合器级联所构成的新型全光开关。理论分析及数值模拟均表明,它同用常系数定向耦合器级联所得的器件相比,具有一个很大的优点,即可以消除开关曲线在过开关区中的振荡,因而具有更好的开关特性;同时,它同用高斯型变耦合系数定向耦合器级联所得的器件相比,具有陡峭的动态开关区(即功率透过率从0逐渐升至1的区域)。综上所述,该级联耦合器更加适合于做全光开关,且在满足一定的开关曲线的要求下,可以通过改变各级联耦合器的参量以改变单元耦合器的数目。     

Omnidirectional and controllable switching behavior in a multiple photonic quantum well system with single-negative material heterostructure

We propose and demonstrate theoretically omnidirectional and controllable switching behavior by combining the advantages of the controllable properties of a photonic quantum well system and the omnidirectional resonant defect modes of single-negative material heterostructures. Our numerical results reveal that the frequency positions of strong localized states are different for odd numbers and even numbers of wells, which can be used to design an all-optical switch by adding or reducing one well. Furthermore, the frequency position can be adjusted by modifying the width of the wells. Compared to conventional all-optical switches, the frequency position of the proposed switch is not only adjustable, but it is also insensitive to the incidence angle of light. The proposed method thus provides a simple way of designing an omnidirectional and controllable all-optical switch.     

双光子吸收对光子晶体定向耦合全光开关的影响

 利用时域有限差分方法,在非线性条件下,考虑双光子吸收效应的同时,建立了分析2维光子晶体定向耦合波导光开关的模型。数值计算结果表明,对于长度较短的波导耦合器件,在强控制光和非线性条件下,双光子吸收效应会对波导的耦合作用产生一定的影响,从而改变入射光的透射特性,使光开关控制的动态过程发生变化。故而在设计全光开关器件时,对强控制光条件下的非线性双光子吸收效应有必要作为影响因素考虑进去。     

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.