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.     

Riemann-Hilbert method and N-soliton for two-component Gerdjikov-Ivanov equation

We consider the Riemann–Hilbert method for initial problem of the vector Gerdjikov–Ivanov equation, and obtain the formula for its N-soliton solution, which is expressed as a ratio of (N + 1) × (N + 1) determinant and N × N determinant. Furthermore, by applying asymptotic analysis, the simple elastic interactions of N-soliton are confirmed, and the shifts of phase and position are also explicitly displayed.     

All-optical switches based on 3 × 3 generalized multimode interference structure

Multimode interference in optical waveguide is attractive for optical signal processing in recent years. In this paper, we propose and design a 3 × 3 all-optical switch using 3 × 3 General Interference Multimode Interference (GI-MMI) structures. Nonlinear directional couplers based on the Kerr effect in two arms of the structure are used as phase shifters. We use chalcogenide glass on silica platform for designing the device structure. The switching states of the device can be controlled by adjusting the optical control signals at the phase shifters in the two arms. The transfer matrix method (TMM) and beam propagation method (BPM) are used for designing and optimizing the device structure.     

Plasmonic all-optical bistable device based on nematic liquid crystal

Low-power all-optical bistable liquid crystal (LC) devices are reported in which surface plasmons propagate along a metallic grating. The threshold switching illumination was 1.4 mW/mm² in the device with the twisted-nematic LC cell. This is a lower value than for all-optical bistable devices reported previously. This low-power bistability device can be used in two-dimensional optical memories or spatial light modulators.     

All-optical switching and strong coupling using tunable whispering-gallery-mode microresonators

We review our recent work on tunable, ultra-high quality factor whispering-gallery-mode bottle microresonators and highlight their applications in non-linear optics and in quantum optics experiments. Our resonators combine ultra-high quality factors of up to Q=3.6×10⁸, a small mode volume, and near-lossless fiber coupling, with a simple and customizable mode structure enabling full tunability. We study, theoretically and experimentally, non-linear all-optical switching via the Kerr effect when the resonator is operated in an add–drop configuration. This allows us to optically route a single-wavelength cw optical signal between two fiber ports with high efficiency. Finally, we report on progress toward strong coupling of single rubidium atoms to an ultra-high Q mode of an actively stabilized bottle microresonator.     

Photoinduced Birefringence and Broadband All-Optical Photonic Switch in a Bacteriorhodopsin/Polymer Composite Film

Photoinduced birefringence with large optical nonlinearity in a bacteriorhodopsin/polymer composite film is observed. A high refractive index change of 8.5×10^-5 photoinduced by 476nm pumping beam is reached at the low intensity of 6.5mW/cm². Based on it, a broadband all-optical photonicswitch is realized with an optical controlling switch system. Because of controlling beam's selectivity in switching, the transporting beams of different wavelengths with different intensities and shapes can be modulated by adjusting the wavelength and intensity of the controlling beam.     

All-optical serial switcher

We present a device that is capable of switching a sequence of equally spaced pulses between two or more outputs, according to the switching information carried from the first pulse, that behaves as an addresser. The device acts as an all-optical serial switcher and it is based on the properties of a soliton beam in a transverse refractive index profile. We further study the interaction force between solitons.     

光致异构聚合物中光学空间孤子的垂直全光调控

用数值方法研究了在具有光致异构非线性的聚合物中光学空间孤子的垂直全光调控.结果表明，对于调控光和信号光是相干的情况，被调控的信号光会产生散射甚至坍塌、微偏转等现象，其作用强弱依赖于两束光的初始相位之差、调控光光强、调控光入射位置等.这种垂直全光调控效应有望应用于全光开光、光集成等方面. 关键词： 光折变空间孤子 孤子相互作用 垂直调控 光致异构     

Carrier concentration dependence of optical Kerr nonlinearity in indium tin oxide films

Optical Kerr nonlinearity (n₂) in n-type indium tin oxide (ITO) films coated on glass substrates has been measured using Z-scans with 200-fs laser pulses at wavelengths ranging from 720 to 780 nm. The magnitudes of the measured nonlinearity in the ITO films were found to be dependent on the carrier concentration with a maximum n₂-value of 4.1×10^-5 cm²/GW at 720-nm wavelength and an electron density of N_d=5.8×10²⁰ cm^-3. The Kerr nonlinearity was also observed to be varied with the laser wavelength. By employing a femtosecond time-resolved optical Kerr effect (OKE) technique, the relaxation time of OKE in the ITO films is determined to be ∼1 ps. These findings suggest that the Kerr nonlinearity in ITO can be tailored by controlling the carrier concentration, which should be highly desirable in optoelectronic devices for ultrafast all-optical switching. PACS 42.65.An; 42.65.Hw; 78.40.Fy     

平面波导型对称星型耦合器的优化设计

通过有限差分波束传播法(FD-BPM)研究了N×N平面波导型星型耦合器的优化设计思想和方法,并通过17×17星型耦合器的模拟设计证明了它的可行性.给出了在输出端引入辅助波导的方法,以提高输出波导阵列的均匀性.并通过模拟计算,分析了圆心缩入程度和锥形区的形状对输出结果的影响.此法也同样适合于N值更大的星型耦合器.     

Design of an insensitive-polarization all-optical switch based on multimode interference structures

This paper presents a new design for an insensitive-polarization all-optical switch using 2 × 2 multimode interference (MMI) couplers. The switching structure can operate at central operating wavelength 1550 nm for both polarizations. A nonlinear directional coupler is used to realize the phase shifter and therefore switching mechanism is obtained. The transfer matrix method and beam propagation method are used to design and optimize the whole device structure.     

Wavelength-conversion type picosecond optical switching using a waveguide QPM-SHG/DFG device

We report picosecond all-optical switching in optical communication band using a LiNbO₃ waveguide quasi-phase matched second-harmonic generation/difference-frequency generation device. Analysis based on the beam propagation method showed that 1 ps switching with 3.1% efficiency is feasible with 10 W peak control pulse power. Switching efficiency of ?22 dB was demonstrated using control pulses of 10 ps width and 2 W peak power.     

All-optical switching in an antiwaveguiding structure

We consider a multichannel optical switch based on a combination of a nonlinear antiwaveguide and several parallel waveguides. The switching is controlled by a perpendicular laser beam focused on the surface of the device. We perform numerical simulations and consider in detail the 1 N switching in such a structure.     

New Criterion for Designing Silica Multimode Interference Power Splitters

We introduce a new criterion for designing 1 × N silica multimode interference power splitters using overlapping-image multimode interference analysis. This criterion requires that widths of multimode waveguides in the devices should be greater than 2 times the product of port number N and effective widths of output waveguides. Better device uniformity can be achieved when the new criterion is satisfied.     

A Novel Proposal for an All-Optical “and” Logic Gate Using Two-Dimensional Photonic Crystals

We present a novel proposal for an all-optical AND logic gate. It is designed based on line and point defects in two-dimensional photonic crystal (PC) rods in air with square lattice. Material of the rods is silicon with dielectric constant 11.56. Dimension of the proposed device is equal to 12.155×12.155 μm. The device elaborated has a simple structure consisting of two inputs – a main output and two idler outputs. Bit rate of the device is equal to 3·10¹² bit/s. Maximum contrast ratio is 5.84 dB. It is a good candidate for optical integrated circuits.     

Ultra-fast all-optical switching in MEH-PPV photonic crystals with resonantly enhanced nonlinearity

Photonic crystal all-optical switching is realized in two-dimensional nonlinear photonic crystals made of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]. Organic polymer films are fabricated by a slow evaporation method. Under resonant excitation, the organic matrix provides very large third-order nonlinear optical susceptibility. An operating pump energy as low as 514 pJ/cm² and a high switching efficiency of 70% are achieved for the photonic crystal optical switching. A switching time of 45.6 ps is maintained due to fast Forster transfer of excitons.     

All optical switching in henna thin film

The optical nonlinearity in henna (Lawson (2- hydroxyl-1,4 naphthoquinone) film was utilized to demonstrate all optical switching. The nonlinear absorption of the henna film was calculated by measuring the transmission of the laser beam (λ = 488 nm) as a function of incident light intensities. The observed nonlinear absorption is attributed to a two-photon absorption process. The pump and probe technique was used to demonstrate all optical switching. The switching characteristics can be utilized to generate all-optical logic gates such as simple inverter switches (NOT) NOR, AND NAND logic functions.     

Miniaturized 90° light path conversion device fabricated from UV-curable resin for optical interconnection

A new 90° light path conversion device incorporating a core element and a hybrid comb-clad that combines air and polymer components is proposed for optical interconnection. The device has a large refractive index difference (Δn) between the core and the hybrid comb-clad, which enables a small curvature radius. Extension to an array of M layers × N channels is straightforward. Ray-tracing simulations indicate that the bending loss is as small as 0.21 dB at the small curvature radius of 0.25 mm. Prototypes were fabricated by the photomask transfer method from two types of UV-curable resin; these prototypes exhibited 90° bending loss of 1.65 dB at a core curvature radius of 0.25 mm.     

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.     

Picosecond cascadable inverter gate using second harmonic pumping

The possibility to realize one all-optical picosecond inverter or one NOR gate has been demonstrated several times. However, the difficult problem of cascading this device (i.e. to use one gate output for driving another gate) is still open. We report in this communication a first step towards simply cascadable logical NOR gates by demonstrating the possible operation of an all-optical inverter which uses an intermediate frequency doubling of the input signal. This implies that a cascadable all-optical NOR gate operating in an “effective” one-wavelength mode (i.e. with an intermediate frequency doubling) is possible. Experiments are carried out on a II–VI compound, namely CdSe, at liquid nitrogen temperature. The inverter operation is investigated around the wavelength 673 nm. The switching energy of the non-linear optical material in this work was 30 μJ/cm² at 337 nm (0.3 pJ/μm²).