All-optical Bistable Switching Research Articles

All-optical bistable switching, hard-limiter and wavelength-controlled power source

In this paper, an all-optical bistable switching operation of resonant-tunneling devices with ultra-small photonic crystal cavity was demonstrated. The whole structure was based on a square lattice photonic crystal formed by rods of refractive index nr= 3.4 in an air background. The cavity was surrounded by eight nonlinear rods of refractive index nL0= 3.1 and nonlinear Kerr coefficient n2= 9 × 10–17 W/m2. Nonlinear finite difference time domain method was used to get a bistability hysteresis loop. Next, all-optical wavelength controlled power source (WCPS), hard-limiter and switching operation based on optical nonlinearity were shown. And that small cavity structure has a small length of 12 mm. Considering the numerous applications and small length, this proposed structure has various potential function in all-optical circuits. Keywords

Optical bistability and multistability driven by external magnetic field in a dielectric slab doped with nanodiamond nitrogen vacancy centres

The theoretical investigation of controlling the optical bistability (OB) and optical multistability (OM) in a dielectric medium doped with nanodiamond nitrogen vacancy centres under optical excitation are reported. The shape of the OB curve from dielectric slab can be tuned by changing the external magnetic field and polarization of the control beam. The effect of the intensity of the control laser field and the frequency detuning of probe laser field on the OB and OM behaviour are also discussed in this paper. The results obtained can be used for realizing an all-optical bistable switching or development of nanoelectronic devices.

Low-cross-talk and high-contrast all optical bistable switching based on coupled defects in a nonlinear photonic crystal cross-waveguide geometry

We present a photonic crystal all-optical bistable switch configuration consisting of crossing perpendicular waveguides geometry with instantaneous Kerr nonlinearity. A microcavity is added to the signal waveguide which is coupled with the defect at the waveguide intersection to increase the transmission contrast. We demonstrate with the finite-difference time-domain method that such a configuration can function as a low crosstalk and high contrast all-optical switch.

Optical bistability based on Fano resonances in single- and double-layer nonlinear slab waveguide gratings

In this paper, we numerically investigate all-optical bistable switching at low input intensity based on Fano resonances available in nonlinear slab waveguide gratings with narrow slits. Fano resonances with various quality factors (Q-factors) in the single- and double-layer slab waveguide gratings are designed and their characteristics are studied by the finite-difference time-domain method. Dependencies on wavelengths of operation, various switching intensities, contrast, and bandwidth of all-optical bistabilities are observed. Comparing nonlinear characteristics of single- and double-layer grating configurations, the latter provides more bistable efficiency with the low input intensities needed and high contrast with high Q-factors at certain operating wavelengths. Both grating configurations in this work provide interesting venues for highly efficient Fano resonance-based all-optical bistable switching devices.

Controlled optical bistability switching in a diode-pumped Tm,Ho:LLF laser

We report on the experimental demonstration of stable all-optical switching between two steady state values of optical bistability from a laser diode end-pumped quasi-three-level Tm,Ho:LLF laser in the 2 μm spectral region. The width of the hysteresis cycle and jump power values can be efficiently controlled by changing the length of the cavity, which is very important to adjust and optimize the optical switching process. The all-optical bistable switching effect is realized by only adding short positive and negative trigger pulses to the pump light. This is, to our knowledge, the first observation of all-optical bistable switching in a rare earth doped solid state laser.

All-optical bistable switching based on photonic crystal slab nanocavity using nonlinear Kerr effect

In this paper, we propose all-optical bistable switching based on a two-dimensional (2D) photonic crystal slab nanocavity using the nonlinear Kerr effect with improved optical properties such as on/off ratio and switching power. The nonlinear properties of different kinds of nanocavity-based L3 structures are characterized. Using the 2D finite-difference time-domain method, we present a new structure of nanocavities for all-optical switching. The device has on/off ratio greater than 15 dB and power smaller than 375 mW for input optical pulses in the range of picoseconds.

Nonvolatile bistable all-optical switch from mechanical buckling

We propose a nonvolatile all-optical bistable optomechanical switch comprising two parallel buckling waveguides. The bistability comes from mechanical buckling so the operation of the switch does not require maintenance power. The switching and reading of the states are all optical; they involve relatively strong and relatively weak optical pulses, respectively, similar to conventional bistable optical switches.

Bistable switching using an optical Tamm cavity with a Kerr medium

All-optical bistable switching is proposed to realize by using an optical Tamm cavity in which a Kerr medium is sandwiched between a metal layer and a Bragg mirror. Results show that the excitation of clockwise and counterclockwise bistable switching under the control of external optical injection is due to the presence of optical Tamm states. In addition, the bistable characteristics of optical Tamm cavities are found to be sensitive to the polarization of external optical injection.

All-optical bistable switching in curved microfiber-coupled photonic crystal resonators

The authors report low-power optical bistability under continuous wave pumping conditions in five-cell photonic crystal linear resonators containing InGaAsP quantum wells, by employing the fiber-coupling technique. The threshold bistable power is measured to be 35μW at the normalized detuning of −1.724. Owing to the high band-edge nonlinearities of quantum wells and the efficient fiber coupling, minimal instability is observed. In addition, all-optical switching is demonstrated with switching energy less than 75.4fJ.

Nonlinear and adiabatic control of high-Q photonic crystal nanocavities

This article overviews our recent studies of ultrahigh-Q and ultrasmall photonic-crystal cavities, and their applications to nonlinear optical processing and novel adiabatic control of light. First, we show our latest achievements of ultrahigh-Q photonic-crystal nanocavities, and present extreme slow-light demonstration. Next, we show all-optical bistable switching and memory operations based on enhanced optical nonlinearity in these nanocavities with extremely low power, and discuss their applicability for realizing chip-scale all-optical logic, such as flip-flop. Finally, we introduce adiabatic tuning of high-Q nanocavities, which leads to novel wavelength conversion and another type of optical memories.

Optical bistable switching action of Si high-Q photonic-crystal nanocavities

We have demonstrated all-optical bistable switching operation of resonant-tunnelling devices with ultra-small high-Q Si photonic-crystal nanocavities. Due to their high Q/V ratio, the switching energy is extremely small in comparison with that of conventional devices using the same optical nonlinear mechanism. We also show that they exhibit all-opticaltransistor action by using two resonant modes. These ultrasmall unique nonlinear bistable devices have potentials to function as various signal processing functions in photonic-crystal-based optical-circuits.

High-contrast all-optical bistable switching in photonic crystal microcavities

We present a bistable photonic crystal configuration consisting of a waveguide sided coupled to a single-mode cavity with instantaneous Kerr nonlinearity. We show that such a configuration can generate extremely high contrast between the bistable states in its transmission with low input power. We also provide an analytic theory that can completely account for the entire transient switching dynamics, as revealed by finite difference time domain simulations.

Polarization-independent all-optical switching in a nonlinear GaInAsP-InP highmesa waveguide with a vertically etched Bragg reflector

We have theoretically designed and experimentally demonstrated polarization-independent all-optical switching in a nonlinear GaInAsP-InP highmesa distributed feedback (DFB) waveguide. The device, which is composed of a highmesa waveguide stripe and a vertically etched Bragg reflector, can be simply fabricated using one-step electron beam lithography and a reactive ion etching process. The device is suitable for integration with other photonic devices such as semiconductor optical amplifiers and wavelength converters. The structural birefringence of the device has a dependence on the waveguide parameters such as the refractive index and thickness of core and cladding. The structural birefringence was successfully eliminated by adjusting the width of the highmesa waveguide. The nonlinear vertical-groove DFB highmesa waveguide is attractive for a polarization-independent all-optical switch from the viewpoint of a large grating coupling coefficient, as compared with a grating-loaded DFB highmesa waveguide. The polarization dependence of the grating coupling coefficient has also been investigated experimentally. It is possible to obtain the polarization-independent grating coupling coefficient by adjusting the grating depth in the vertical-groove DFB highmesa waveguide, together with structural zero-birefringence of the device. Polarization-independent all-optical thresholding and bistable switching operations have been successfully demonstrated in the nonlinear vertical-groove DFB highmesa waveguide.

Dependence of threshold switching power on the control-light wavelength in a nonlinear distributed-feedback GaInAsP waveguide

We demonstrate all-optical bistable switching by using orthogonally and parallelly polarized control light in a nonlinear distributed feedback GaInAsP waveguide. When the control light that is orthogonally polarized to the signal light is within its stopband, it is possible to extract the signal without using any external devices. Also, we investigate theoretically and experimentally the dependence of threshold switching power on the wavelength and polarization of control light.

All-optical bistable switching in nonlinear directional coupler loaded with Bragg reflector

A GaInAsP nonlinear directional coupler loaded with a Bragg reflector has been fabricated. All-optical bistable switching in the fabricated device is demonstrated at a wavelength of 1.55 /spl mu/m.

All-optical bistable switching dynamics in 1.55-μm two-segment strained multiquantum-well distributed-feedback lasers

All-optical bistable switching dynamics of 1.55-/spl mu/m two-segment strained multiquantum-well (MQW) distributed-feedback (DFB) lasers were systematically studied both experimentally and theoretically. Some fundamental optical functionalities, including all-optical set-reset (flip-flop) operations, were demonstrated. The switching responses of these bistable lasers were studied, for the first time, with optical injection from a single-mode DFB laser, indicating that the switching dynamics based on gain quenching and absorption saturation are inherently different. A theoretical model including optical injection was developed to study these all-optical bistable switching characteristics in segmented bistable lasers. It was found that the nonuniform distribution of the photon density in the bistable laser cavity induced by optical injection was essential to perform the time-domain switching operations. Simulations showed a good agreement with experimental observations and indicated design improvements. Although the switching responses in the range of tens of picoseconds can be obtained with these bistable lasers, the maximum repetition frequency of the bistable systems would still be limited to the hundreds of megahertz due to the slow carrier recovery time (5 ns) of the lasers.

All-optical bistable switching in a strained piezoelectric self-electro-optic effect device

The authors demonstrate that symmetric self-electro-optic effect devices which use strained piezoelectric quantum wells can exhibit bistable switching without external bias. A design philosophy and experimental results for InGaAs on (111) GaAs are presented.

All-optical bistable switching and signal regeneration in a semiconductor layered distributed-feedback/Fabry–Perot structure

We report the experimental observation of optical bistable switching in a combined distributed-feedback/Fabry–Perot structure. The sample had a high switching contrast with almost zero reflectivity in the on-state. A turnoff time as short as 4 ns was measured. The threshold power for bistability was about 2 mW. Bistable switching with the memory effect and a potential application for all-optical signal regeneration were demonstrated.

All-optical bistable switching in an active InGaAs quantum-well waveguide

The authors have observed low-power optical bistability in an active strained InGaAs single-quantum-well waveguide which is biased with a quasi-constant current injection 20% below the threshold current. Although the output power measured after the output collecting lens is half of the peak input power measured before the input focusing lens, it is believed that this is mainly due to the inefficient coupling into a slab mode, and that optical switching occurs with net gain in the device. A channel waveguide with a similar active medium would operate with constant DC electrical bias and should provide significant overall gain. >

Saturating refractive non-linearities and optical bistability: implications for excitonic switching

We examine the operation of a refractive Fabry-Perot bistable device and consider the importance of saturation of the non-linear refraction using a simple model. A condition is formally derived which determines whether a particular material with a limited refractive index change may be used to make an all-optical bistable switch. This is evaluated for the GaAs/AlGaAs quantum-well system by comparison with four-wave mixing measurements of the non-linear refraction associated with the exciton feature.