Polarization Control Devices Research Articles

Cascaded dynamic eigenstates of polarization analysis for piezoelectric polarization control

We propose the cascaded dynamic eigenstates (DESs) of polarization to analyze multicomponent polarization control (PC) devices, and achieve the analytical expression of output state of polarization (SOP) as a function of voltage for piezoelectric polarization control (PPC). By measuring the DES at the output port of the device, the prestage DESs will rotate around subsequent ones. Experimental results in PPC confirm the validity of our analysis. The average error of our theoretical output SOP is 1.23 degrees, and the SOP response time is ~10 micros, which is promising to realize a quasi-open-loop high-speed PC.

Self-Controlled Short Pulse Generator from All-Fiber Coupled Fabry-Perot Cavity

Self-controlled sub-nanosecond pulse generator was demonstrated with an ytterbium-doped fiber. This fiber laser consisted simply of all non-polarization fiber without any devices for polarization control and birefringence compensation. The self-pulse operation system gave an average output power of 0.9 mW in 800-ps duration pulses.

Self-Starting Pulse Generation from Cooled Erbium-Doped Fiber Ring Laser

A self-starting pulse laser with an erbium-doped fiber cooled at liquid-nitrogen temperature was demonstrated. The self-starting-pulse fiber-ring laser can produce an approximately 1 ns pulse train without the need for devices for polarization control and compensation of birefringence.

Pancharatnam-Berry phase optical elements for wave front shaping in the visible domain: Switchable helical mode generation

We report the realization of a Pancharatnam-Berry phase optical element [Z. Bomzon, G. Biener, V. Kleiner, and E. Hasman, Opt. Lett. 27, 1141 (2002)], for wave front shaping working in the visible spectral domain, based on patterned liquid crystal technology. This device generates helical modes of visible light with the possibility of electro-optically switching between opposite helicities by controlling the handedness of the input circular polarization. By cascading this approach, fast switching among multiple wave front helicities can be achieved, with potential applications to multistate optical information encoding. The approach demonstrated here can be generalized to other polarization-controlled devices for wave front shaping, such as switchable lenses, beam splitters, and holographic elements.

Nanophotonic devices for polarization control

Nanophotonic devices for polarization control

Simultaneous strain and temperature sensor based on the numerical reconstruction of polarization maintaining fiber Bragg gratings

When a short-length fiber Bragg grating is inscribed into a polarization-maintaining fiber, the resonant peaks produced by birefringence can overlap. In this case, the discrimination between strain and temperature effects is only possible by means of polarization control devices, i.e. a linear polarizer and a polarization controller. To avoid this complexity and the measurement errors that it involves, we propose a novel demodulation technique based on the numerical reconstruction of the grating physical parameters. Our technique evaluates the grating parameters from the amplitude spectrum by means of the coupled-mode equations. The convergence tool used to search the solutions is the Nelder–Mead simplex algorithm. The method is tested on uniform and apodized Bragg gratings and a very good accuracy is reported. The method is finally applied to a 2 mm-long uniform polarization-maintaining grating in order to simultaneously measure longitudinal strain and temperature.

A design of reflection‐type polarization control device using ferroelectric liquid crystals

AbstractFor a planar polarization control optical switch proposed by the authors for optical communication networks, a reflection‐type liquid crystal polarization control device (PCD) that can emit the incident wave in the same direction as the incident after totally reflected on the back side and can accurately switch the polarization direction of the optical wave by 90° in response to an applied voltage is needed. The authors have previously derived and reported a design theory for accurate switching of the polarization direction for an obliquely incident ferroelectric liquid crystal polarization control device (FLC‐PCD) in which the light wave is obliquely incident upon the device surface at an arbitrary angle and transmits to the back side. In the present paper, based on this theory, the polarization control characteristics are theoretically analyzed by means of the Jones matrix with respect to the reflection‐type FLC‐PCD, in which the incident wave is totally reflected at the back side of the device and is returned to the incident side. The condition for accurate switching of the polarization direction of the output wave by 90° is derived. Based on this condition, a method for derivation of the optimum design values of the liquid crystal layer thickness and liquid crystal optical axis angle is presented. The polarization control characteristics of the device fabricated for trial are measured, demonstrating the validity of the present design method. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 87(1): 43–53, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10038

Magneto-optic-based devices for polarization control

In this paper we present a number of measurements of the magneto-optic (MO) polarization rotation effect in MO glasses. We then show three design concepts of MO based devices that are of interest for optical communications applications. The first device is a tunable optical polarization controller, the second is a polarization filter that passes through only a specific point on the Poincare sphere and the third is a MO Fabry–Perot resonator that enhances the MO effect and can be used inside an all-optical switch or as part of a polarization coding module.

Optical Constants of Two Typical Liquid Crystals 5CB and PCH5 in the THz Frequency Range.

The complex refractive indices of two benchmark nematic liquid crystal,4-4 '-n-pentyl-cyanobiphenyl (5CB) and 4-(trans-4'pentylcyclohexyl)-benzonitrile (PCH5) have been determinedin the frequency range from 0.2 to 0.8 THz. The technique of coherent THztime-domain spectroscopy (THz-TDS) was used. We show that the birefringenceof 5CB is in the range of 0.15 to 0.21, while that of PCH is from 0.01 to0.08. Both liquid crystals exhibit relatively small absorption in thisfrequency range. The large birefringence of 5CB indicates possible applications of liquid-crystal-based devices for modulation and polarizationcontrol of electromagnetic radiation in the THz frequency range.

High performance Feussner-type polarizers based on stretched poly(ethylene-terephthalate) films

Stretched poly(ethylene-terephthalate) films appear to be an interesting optical plastic for use in polarization control devices. By means of stretching ratios its birefringence, in practice, can be tailored from ∼0 to ∼0.17. It has a very wide transmission window (∼0.32–5.70 μm) and good thermal, mechanical, and chemical properties. We propose using it for polarizers based on the Feussner design. By implementing this configuration with a biaxially stretched film, we have obtained a polarizer with an achromatic extinction ratio better than 1 part in 50 000. This is comparable with conventional Glan–Thompson polarizers but with additional advantages. The principal refractive indices of the film (in the 0.43–5.7 μm range) and the operational range of the polarizer presented are also provided.

A design theory of ferroelectric liquid crystal polarization control device for tilted incident light angle

A design theory of ferroelectric liquid crystal polarization control device for tilted incident light angle

A design theory of ferroelectric liquid crystal polarization control device for tilted incident light angle

AbstractAs a form of free‐space‐type optical switch, the authors have proposed a planar polarization control‐type optical switch. The present paper reports the design theory for a liquid crystal polarization control device with a tilted incidence angle as a key device for this switch. Since the switching of the optical paths by the polarization control of a liquid crystal is used as the operating principle, it is necessary to develop a device that can accurately change the direction of polarization of the beam incidence tilted from the crystal plane by 90° by an applied voltage. It has been known experimentally that a device with a characteristic close to this requirement can exist. A general design method has not been reported. In this paper, for the device made of ferroelectric liquid crystal, the polarization control characteristic is theoretically analyzed by the Jones matrix so that the condition for changing the polarization direction of the output light exactly by 90° is derived. Based on this finding, the optimum design values of the layer thickness and optical axis of the liquid crystal are numerically obtained. The polarization control characteristics of the fabricated device for a wavelength of 0.85 µm are measured and the validity of the present design method is demonstrated. © 2002 Scripta Technica, Electron Comm Jpn Pt 2, 85(3): 30–39, 2002

Spectroscopic polarimetry with a channeled spectrum

We describe a novel method for the spectroscopic measurement of the state of polarization (SOP) of light. A pair of thick birefringent retarders is incorporated into the spectroscopic polarimeter, so the generated channeled spectrum is composed of three quasi-cosinusoidal components carrying the information about the SOP of the light that is being measured. Fourier inversion of the channeled spectrum provides significant parameters for determination of the spectrally resolved Stokes parameters of light. No mechanically movable components for polarization control or active devices for polarization modulation are used, and all the Stokes parameters can be determined at once from only the single spectrum. The effectiveness of this method is demonstrated by the generation of elliptically polarized light whose SOP varies with wave number.

A theoretical model for ferroelectric polarization-controlled superconductor devices

Polarization-controlled superconductor devices could be used as a logic gate or other electronic units such as acoustic sensors, electro-optical transducers and image detectors. Lin and Wu (Appl. Phys. Lett. 65 (8) (1994) 1) have experimentally investigated the I–V characteristics of such a device. In this paper, we propose a theoretical model to calculate the polarization effect on the I–V curves. The polarization effects include the cause of the superconducting-normal state switching and exponential time dependence of the source-drain voltage. We fit the experimental data with the theoretical model. They agree quite well.

Endlos-Polarisationsregelung für den optischen Phasendiversitätsempfang

Polarization fluctuations at the end of a single-mode fibre can severely reduce the sensitivity of a coherent optical receiver. This can be avoided by an active polarization control unit. A new control algorithm is presented that is designed for a phase diversity receiver. In each operation step the distance between the actual retardation and the physical range limits is maximized. Thus reset procedures of the utilized finite-range polarization control devices can be avoided. Simulations of the new scheme showed that the sensitivity degradation is less than 0.8 dB.

Novel Vitrified Liquid Crystals and Potential Applications

AbstractAn overview is presented for a generic approach to low molar mass liquid crystalline materials capable of vitrification into morphologically stable, optically anisotropic thin films. Potential applications as polarization control devices, optical notch filters, and luminescent elements will be explored. Preliminary data for defect formation and annihilation will also be presented to illustrate an advantage of low molar mass materials over polymer analogs.

Polarization-dependent refractive-index change induced by superlattice disordering

A model of the polarization-dependent refractive-index change that accompanies superlattice disordering is proposed for the first time. Calculated results agree well with experimental results in terms of the amount and direction of the refractive-index changes. In the GaAs-AlAs system, a simple diffusion model that considers the diffusion of group III atoms explains the experimental results. In a InGaAs-InP system, it is assumed that group V atoms mainly induce disordering, and the difference between the diffusion constant in wells and that in barriers is taken into account. The refractive-index changes induced by superlattice disordering are useful for fabricating polarization control devices and integrated optical circuits.

Ferroelectric liquid-crystal polarization-control devices with a double-layer cell structure

We analyzed the polarization-switching characteristics of a ferroelectric liquid-crystal polarization control device using a double-layer cell structure for free-space optical processing and switching systems. We theoretically derived the optimum arrangement of layered cells for 90° polarization switching. The theory shows that the optimum parameter range for the double-layer cell structure is wider than that for a single-layer cell. We verified our theory by measuring the polarization cross talk of experimental polarization control devices.

Simultaneous blue- and red-shift of light-hole and heavy-hole band in a novel variable-strain quantum well heterostructure

We have designed and studied a new type of strained semiconductor quantum well structure, variable-strain quantum well. The strain within the quantum well is graded from compressive to tensile in order to obtain mutually opposing slopes for the heavy- and light-hole band edges, causing the heavy and light holes to experience opposite fields created by the same strain. A unique bias controlled crossover with a simultaneous red and blue quantum confined Stark shift for the heavy- and light-hole transitions, respectively, has been observed by electroreflectance spectra. This results in a bias controlled change of the polarization properties and the transition energies suitable for polarization controllable photonic devices.

Geometrical shape dependent polarization anisotropy in electroluminescence from InGaAs/InP quantum wires

The polarization properties of edge-emitted electroluminescence from InGaAs/InP quantum wires fabricated by reverse-mesa wet etching, electron-beam lithography, and overgrowth, are investigated. Strongly TE polarized electroluminescence from relatively wide wires approaches isotropy as the wires become narrower. The observed dependence on wire size is attributed to a transition from a two-dimensional to a one-dimensional system. The implication is that quantum wires could potentially be applied to polarization-controlled devices, such as polarization insensitive optical amplifiers.