Optical Polarization Switching Research Articles

All-Optical NRZ-OOK to BPSK Format Conversion in an SOA-Based Nonlinear Polarization Switch

All-optical format conversion from nonreturn-to-zero on-off keying to binary phase-shift keying is demonstrated in a semiconductor optical amplifier-based nonlinear polarization switch. This conversion is realized by cross-phase modulation effect for phase encoding and nonlinear polarization rotation effect for amplitude equalization. In the experiment, error-free operation at 10 Gb/s is achieved with a receiver sensitivity penalty of 1.3 dB after single-ended detection.

Several Types of Bilayer Smectic Liquid Crystals with Ferroelectric and Antiferroelectric Properties in Binary Mixture of Dimeric Compounds

The mesomorphic behavior and phase structure were examined in the mixture of two kinds of dimeric compounds, alpha,omega-bis(4-alkoxyanilinebenzylidene-4'-carbonyloxy)pentane (mOAM5AMOm), by optical microscopy, X-ray diffraction, polarization switching, and second-harmonic generation measurements. One compound is 4OAM5AMO4 with a short terminal alkyl chain that forms a single-layer smectic phase (SmCAs) with a random mixing of spacer and tail groups. Another compound is 16OAM5AMO16 with a long terminal alkyl chain that forms a chiral, anticlinic, and antiferroelectric bilayer phase (SmCAb) with the bent molecules tilted to the bilayer. By mixing these two compounds, the SmCAs phase of 4OAM5AMO4 is easily destabilized, leading to the wide content region of the bilayer phases. In the bilayer regime, three other smectic phases are newly induced. Two of them are antiferroelectric and ferroelectric phases in which the molecules lie perpendicularly with respect to the layer. The other shows no polar response to an external electric field and behaves like a smectic A. The new appearance of these bilayer phases is discussed as a mixing effect of long and short tail groups.

SOA-based all-optical switch with subpicosecond full recovery

We investigate all-optical switching in a multi-quantum-well semiconductor optical amplifier-based nonlinear polarization switch using optical pulses with duration of 200 fs at a central wavelength of 1520 nm. We show full recovery of the switch within 600 fs, in both the gain and absorption regime. We discuss the switching and recovery mechanisms using numerical simulations that are in qualitatively good agreement with our experimental data.

Quantum-well band structure effects on the emission polarization from a spin-polarized electron reservoir

Many spin-polarized-based devices utilize the optical polarization from semiconductor quantum wells (QWs) as a read out. Under ideal conditions at zero crystal momentum, 100% optical polarization is obtained from these QWs for fully polarized electrons. However, carrier populations typically extend over nonzero crystal momentum states, where band mixing results in nonideal optical polarization. We investigate a single InxGa1−xAs(x=0.2, and 0.08)QW in GaAs in a typical p-i-n spin injector structure, using eight band k.p theory including strain, electric field and quantum-confined Stark effects. By evaluating the carrier distribution and wave functions of the QW states, we find the resulting optical polarization is reduced to ∼60% at 10K, and further for high temperature and high fields. We show that under certain conditions we can flip the sign of the optical polarization, suggesting the possibility of an electric field controlled optical or spin polarization switch.

Polarization Switching by TM Passing of Laminated Cover

This paper investigates transverse-electric-transverse-magnetic (TM) conversion properties of an integrated optical polarization switch realized by means of a TM-pass waveguide polarizer, whose cladding consists of an obliquely deposited thick film. This waveguide polarizer is more compact, stable, and inexpensive to realize than a hybrid waveguide polarizer using birefringent crystal as cladding. By utilizing the TM-passing property of the anisotropic cover of a rib waveguide, the polarization is selected by means of the electrooptic effect.

OPTICAL TRANSMISSION AND POLARIZATION SWITCHING PROPERTIES OF A FERROELECTRIC LIQUID CRYSTAL CELL WITH A STABLE TWISTED STATE

Ferroelectric liquid crystal cells with a stable twisted state were prepared. Dynamic processes of molecular reorientation in a stable twisted state under an applied electric field have been investigated by observing the optical transmittance and polarization switching current with simultaneous observation of the texture change.

Liquid-crystal-electrochromic-material interface: a p-n-like electro-optic junction.

A liquid crystal (LC) cell has been made by using a standard sandwich configuration with one of the indium tin oxide (ITO) electrodes covered by a thin layer of tungsten trioxide (WO3). In this kind of cell optical polarization switching (observed under a crossed polarizer microscope) occurs for only one of the two polarities of an ac external applied electric field, while in the usual liquid crystal cells the electro-optic response does not depend on the sign of the field. The inhibiting switching configuration corresponds to anodic polarization of the tungsten trioxide film in which the deintercalation of cations occurs. Here we present the time behavior of charge and discharge for both the anodic and cathodic currents. A model based on charge carrier exchange between the ITO-WO3 and WO3-LC interfaces and also electrochemical processes is reported. Our model is also capable of explaining the electric and electro-optic asymmetric responses of the cell. Numerical calculations confirm the model.

Spin relaxation and all optical polarization switching at 1.52 micrometres in InGaAs(P)/InGaAsP multiple quantum wells

The spin relaxation times of electrons in InGaAs(P)/InGaAsP multiple quantum wells have been directly measured as a function of well width using an ultrashort pulse colour centre laser. The times measured range from 20 to 5 ps, considerably faster than previously determined in GaAs quantum wells. In addition, a fast, all-optical polarization switch based on a spin-sensitive optical nonlinearity is demonstrated at a wavelength of . This operating wavelength and the observed switch recovery time of 5.5 ps make it a potentially useful element for future all-optical soliton communication systems.

High signal-to-noise ratio birefringence-compensated optical delay line based on a noise-reduction scheme

A multichannel fiber-optic delay-line architecture based on optical polarization switching is proposed that uses non-polarization-maintaining optical fibers. Critical birefringence-compensation and noise-reduction techniques are introduced and demonstrated for these delay lines, which show a high optical polarization extinction ratio (>39 dB) and a high electrical signal-to-noise ratio (>92 dB).

Optical polarization switching in a Fabry–Perot étalon that utilizes the photoinduced Kerr effect

We present an all-optical polarization switching of an asymmetric Fabry-Perot étalon containing a nonlinear Kerr medium in reflection type. Reflectance of a signal wave breaks up into two orthogonal polarization components as a result of photoinduced birefringent effects and shows distinct features of intensity stability and a high extinction ratio in polarization switching-modulation and memory operations.

Optical amplification and polarization switching in a birefringent nonlinear optical medium: An analysis

In birefringent nonlinear optical media, it is shown that phase-matched wave-mixing processes occur naturally among the extraordinary and ordinary wave components of a strong pump and a weak probe beam. The necessary and sufficient conditions that these parametric processes may lead to amplification and or polarization switching of the probe beam are quantitatively analyzed.

Horseshoe chaos in a periodically perturbed polarized optical beam

The problem of a single, polarized, laser pulse propagating as a travelling wave in an anisotropic, cubically nonlinear, lossless medium is investigated as a Hamiltonian system. This Hamiltonian system describes the travelling-wave dynamics of two nonlinearly coupled complex laser modes. Invariance of the Hamiltonian function under changes of phase of the complex two-component electric field amplitude reduces the phase space to the two-sphere, S 2, on which the problem is completely integrable. The fixed points and bifurcations of the phase portrait on S 2 are studied as the beam intensity and medium parameters are varied, and homoclinic and heteroclinic connections are identified in each parameter domain. Horseshoe chaos is analytically shown to arise when the optical parameters of the medium are perturbed due to spatially periodic inhomogeneities, by using the Melnikov method. The resulting sensitive dependence on initial conditions has implications for the control and predictability of nonlinear optical polarization switching in birefringent media.