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.     

Nonlinear directional coupler based on Rb:KTP-waveguides

We propose the use of KTP-based waveguides for all-optical switching. The passing of subnanosecond light pulses through the Rb:KTP nonlinear directional coupler is investigated. The nonlinear switching of 40% of light power from the one channel to another is observed at 5 kW input power.     

Photosensitivity of As2S3 chalcogenide thin films at 1.5 microm

Chalcogenide glasses are promising candidates for all-optical switching and various nonlinear applications. However, we show that As2S3 thin films are photosensitive at wavelengths in the 1.5-microm telecommunication window. This sensitivity is evidenced by the formation of self-written waveguides in slabs, where channels as narrow as 1 microm are created. We also show the detrimental effects of such photosensitivity in ridge waveguides. This photosensitivity seems to occur only in thin-film form and not in bulk samples or fibers.     

Nonlinear directional coupler in periodically poled lithium niobate

Nonlinear wave propagation was investigated experimentally in coupled waveguides by means of the cascaded nonlinearity in quasi-phase-matched second-harmonic generation. With a specially designed wave-vector-mismatch distribution along the propagation axis, cascading was optimized for low fundamental depletion. High-contrast, ultrafast all-optical switching with switching powers of tens of watts was observed.     

Coupled-Soliton All-Optical Logic Device with Two Parallel Tapered Waveguides

In this article, a new all-optical logic device by using the interaction of spatial solitons has been proposed. The operation of the proposed device is based on the evolution of a nonlinear guided wave propagating along two parallel tapered waveguides with a Kerr-type nonlinear medium between them. The numerical results show that this device could be potentially useful in several all-optical logic functions (AND, OR, and XOR).     

Coupled-Soliton All-Optical Logic Device with Two Parallel Tapered Waveguides

In this article, a new all-optical logic device by using the interaction of spatial solitons has been proposed. The operation of the proposed device is based on the evolution of a nonlinear guided wave propagating along two parallel tapered waveguides with a Kerr-type nonlinear medium between them. The numerical results show that this device could be potentially useful in several all-optical logic functions (AND, OR, and XOR).     

Photonic switching in GaAlAs optical strip waveguides by photo-induced electroabsorption

GaAlAs strip waveguides embedded in unbiased pn-junctions are employed for all-optical switching. The underlying physical mechanism is a combination of the photovoltaic effect and the conventional Franz-Keldysh effect, thus it is called the photo-induced Franz-Keldysh effect or photo-induced electroabsorption. Experimental as well as theoretical results are given and show good agreement. In the experiments the transmitted light power of a probe beam is switched by 3 dB due to an injected control beam at input light power levels of about 0.5 mW each. The dynamics of this all-optical switch is limited by RC time constants.     

High speed logic gate using two-photon absorption in silicon waveguides

The switching speed of conventional silicon-based optical switching devices based on plasma dispersion effect is limited by the lifetime of free carriers which introduce either phase or absorption changes. Here we report an all-optical logic NOR gate which does not rely on free carriers but instead uses two-photon absorption. High speed operation was achieved using pump induced non-degenerate two-photon absorption inside the submicron size silicon wire waveguides. The device required low pulse energy (few pJ) for logic gate operation.     

纳米光子学全光开关研究进展

全光开关是全光网络和数字光信息处理的基本器件,该器件主要基于非线性光学原理．自激光发明以来,对该器件的研究已历时半个世纪．虽然全光开关的基础研究十分活跃,研究成果丰硕,但是至今尚未做出实用器件．文章分析了全光开关面临的困难,指出只有在极小的时空条件下,也就是采用飞秒激光驱动的纳米尺寸器件,才有可能研制出低开关功率、高开关速度、低插入损耗的实用的全光开关器件．文章简要介绍了近10年来纳米全光开关的研究成果,包括纳米尺寸干涉仪开关（空间开关）、量子限制光双稳触发器（时间开关）、半导体光放大器的波长转换器（波长开关）、光子晶体带隙移动开关和表面等离子体激元开关（强度开关）等5类16种典型的纳米全光开关器件．     

Enhanced all-optical tuning of leaky eigenmodes in photonic crystal waveguides

We demonstrate all-optical switching in an active two-dimensional photonic crystal waveguide, observing as large as 16 nm blueshifts of a leaky eigenmode at 839 nm and switching ratios of almost 70%. These results are larger than those previously observed in similar experiments performed on passive photonic crystal waveguides; the enhancement is due to resonant photogeneration of carriers by In(0.12)Al(0.2)Ga(0.68)As quantum wells in the core of the waveguide. The effective change in the refractive index of the structure is approximately10(-2), with a rise time of approximately1 ps and a decay time of approximately10 ps, potentially allowing high-speed switching and fast modulation rates.     

MZ-MMI-based all-optical switch using nonlinear coupled waveguides

We propose an all-optical switch (AOS) based on Mach-Zehnder (MZ) and Multi-mode interference (MMI) using nonlinear closely coupled waveguides. The device operates by switching between two states of coupled waveguides. In first state the refractive index of waveguides are same and light field will completely couple to nonlinear waveguide in half length of coupler and will back in the second half. We will have π phase difference in this procedure and the input field will appear in Bar-state output. In the second state the refractive index of nonlinear waveguide increase with high intensity control field. In this case, we have lower coupling and change in phase. But, we choose the best refractive index change to obtain the phase change of multiple of 2π necessary for Cross-state in output. The beam propagation method is used to simulate the device operation.     

The propagation of wave beams in 2D cascade-induced lattices

A new method of 2D periodic lattices excitation in quadratically nonlinear media with cascade interaction is suggested. It is shown that in such structures the all-optical management of laser beams could be carried out. The possibility of switching waveguides and changing the final energy distribution among channels using the phenomenon of discrete diffraction is demonstrated.     

Shaping and switching of polychromatic light in arrays of periodically curved nonlinear waveguides

We overview our recent theoretical results on spatio-spectral control, diffraction management, and broadband all-optical switching of polychromatic light in periodically curved one and two dimensional arrays of coupled optical waveguides. In particular, we show that polychromatic light beams and patterns produced by white-light and supercontinuum sources can experience wavelength-independent normal, anomalous, or zero diffraction in specially designed structures. We also demonstrate that in the nonlinear regime, it is possible to achieve broadband all-optical switching of polychromatic light in a directional waveguide coupler with special bending of the waveguide axes. Our results suggest novel opportunities for creation of all-optical logical gates and switches which can operate in a very broad frequency region, e.g., covering the entire visible spectrum. Presented at 9-th International Workshop on Nonlinear Optics Applications, NOA 2007, May 17–20, 2007, Świnoujście, Poland     

On the concept of a resonant tunneling photonic nanotriode

The concept of a resonant tunneling photonic nanotriode that allows the mutual all-optical control of cross-cut light flows is developed. The concept is based on the strong resonant interaction between the quasi-localized eigenmode of nonlinear planar dielectric waveguides and incident beams. It is demonstrated that small variations of input guided wave intensities may result in deep modulation of beam reflection and transmission coefficients.     

Design of ultra compact all-optical XOR and AND logic gates with low power consumption

We propose a novel ultra-compact all-optical XOR and AND logic gates without using nonlinear optics. In order to realize these devices, we adopt photonic crystal waveguides (PCWs) based on multi-mode interference devices. Numerical results show that the operating bandwidth of the ON to OFF logic-level contrast ratio of not less than 6.79 dB is 35 nm for XOR logic gate and 9 nm for AND logic gate. Proposed logic gates have the potential to be key components for an optical packet switching system due to their small feature sizes and low power consumption.     

Highly efficient second-harmonic generation in buried waveguides formed by annealed and reverse proton exchange in periodically poled lithium niobate

Efficient three-wave mixing devices have numerous applications, including wavelength conversion, dispersion compensation, and all-optical switching. Second-harmonic generation (SHG) is a useful diagnostic for near-degenerate operation of these devices. With buried waveguides formed in periodically poled lithium niobate by annealed and reverse proton exchange, we demonstrate what is believed to be the highest normalized conversion efficiency (150%/W cm(2)) for SHG in the 1550-nm communications band reported to date.     

Enhanced linear and nonlinear optical phase response of AlGaAs microring resonators

We have constructed and characterized several optical microring resonators with scale sizes of the order of 10 microm. These devices are intended to serve as building blocks for engineerable linear and nonlinear photonic media. Light is guided vertically by an epitaxially grown structure and transversely by deeply etched air-clad sidewalls. We report on the spectral phase transfer characteristics of such resonators. We also report the observation of a pi-rad Kerr nonlinear phase shift accumulated in a single compact ring resonator evidenced by all-optical switching between output ports of a resonator-enhanced Mach-Zehnder interferometer.     

Strong optical non-linearities for efficient all-optical switching in GaAlAs waveguides

The light intensity transmission of GaAlAs strip waveguides is sensitively dependent on the strength of the electric field inside the waveguide, when the photon energy is close to the band gap (Franz-Keldysh effect). In a waveguide embedded in a pn-junction the transmitted light itself induces the field changes through the photoelectric effect. This photo-induced Franz-Keldysh effect causes a non-linear intensity transmission of the waveguide. Light power levels far below 1 mW are sufficient to give strong non-linearities. Possible application schemes for modulation and all-optical switching in integrated optics and optoelectronics are discussed.     

Phase-controlled all-optical switching based on coherent population oscillation in a two-level system

We theoretically propose a scheme of phase-controlled all-optical switching due to the effect of degenerate four-wave mixing (FWM) and coherent population oscillation (CPO) in a two-level system driven by a strong coupling field and two weak symmetrically detuned fields. The results show that the phase of the FWM field can be utilized to switch between constructive and destructive interference, which can lead to the transmission or attenuation of the probe field and thus switch the field on or off. We also find the intensity of the coupling field and the propagation distance have great influence on the performance of the switching. In our scheme, due to the quick response in semiconductor systems, a fast all-optical switching can be realized at low light level.     

Integrated all-optical nonlinear device for re- configurable add/drop and wavelength shifting of WDM signals

A novel configuration is proposed for an all-optical device performing two key functionalities in a communication network based on wavelength-division-multiplexing (WDM): reconfigurable add/drop and wavelength shifting of single channels. The device is based on guided second-order nonlinear interactions, such as sum-frequency generation and difference-frequency generation, between the WDM channels and a suitable pump beam. A directional coupler and two parallel waveguides allow the spatial separation between the main WDM signal and the dropped or wavelength-shifted channel for a subsequent routing in the desired path. A first numerical simulation provided a cross-talk level in the dropped channel lower than -41 dB and a wavelength-shifting range of more than 40 nm. Received: 18 May 2001 / Published online: 30 October 2001