Method for measuring off-diagonal Kerr coefficients by using polarized light transmission

We report a method for measuring the off-diagonal coefficients of the quadratic electro-optic (Kerr) tensor by using polarized light transmission. The method relies on designing an experimental configuration in which the linear electro-optic (Pockels) effect does not contribute to the data. Our method can be used to obtain off-diagonal Kerr coefficients for all but two of the 20 crystal point groups for which the Pockels effect and the Kerr effect coexist. Our theoretical model includes effects from transmission, multiple reflections, and electrostriction but neglects absorption in the crystal. To verify the method, we used it to measure the R12 and R13 Kerr coefficients for a (100)-type single crystal of ferroelectric barium titanate (BaTiO3) at room temperature (23.5 degrees). To our knowledge, this is the first time this method has been used and the first time these coefficients have been measured for the unclamped crystal in the tetragonal state. The mean values obtained with this method are R12 = -3.5+/-0.3 x 10(-17) m2/V2 and R13 = -8.0+/-0.7 x 10(-17) m2/V2.     

Proposal for electro-optic multiplier based on dual transverse electro-optic Kerr effect

A novel electro-optic multiplier is proposed, which can perform voltage multiplication operation by use of the Kerr medium exhibiting dual transverse electro-optic Kerr effect. In this kind of Kerr medium, electro-optic phase retardation is proportional to the square of its applied electric field, and orientations of the field-induced birefringent axes are only related to the direction of the field. Based on this effect, we can design an electro-optic multiplier by selecting the crystals of 6/mmm, 432, and m3m classes and isotropic Kerr media such as glass. Simple calculation demonstrates that a kind of glass-ceramic material with a large Kerr constant can be used for the design of the proposed electro-optic multiplier.     

La3Ga5SiQ14 single-crystal Q switch used as an electro-optic device

A new kind of electro-optic Q switch is designed by use of a La3Ga5SiQ14 (LGS) crystal. Because the LGS crystal is optically active, the Q switch is based on the consideration that the total rotation angle of the polarization plane is zero, whereas the polarized wave propagates through the Pockels cell back and forth, with the polarization plane gyration and electro-optic effect existing simultaneously. The LGS Q switch is a practical electro-optic device that can be used in medium output energy lasers to partially take the place of deuterated potassium dihydrogen phosphate and lithium niobate Q switches.     

Diffraction light modulator based on transverse electro-optic effect in short-pitch ferroelectric liquid crystals

A diffraction modulator that exploits the transverse electro-optic effect in ferroelectric liquid crystals is proposed for applications in displays and in spatial light modulators. Experiments with a short-pitch ferroelectric liquid crystal aligned homeotropically show an achromatic contrast ratio of greater than 100:1 available with oblique readout. The sources of the contrast deterioration and the tolerance of the proposed scheme to this deterioration are analyzed. For selected directions of readout the light output obtains low sensitivity to the polarization of the readout light. Nonlaser light sources can be used in a practical display setup based on the proposed principle.     

Comparative study of nonlinear optical crystals for electro-optic Q-switching of laser resonators

The development of Pockels cells is closely related to the choice of the crystals which are involved in this kind of device. These crystals must satisfy several requirements. In order to clearly establish the crystal ability for the realization of Pockels cells, we define several figures of merit describing its performances for electro-optic Q-Switch and we use these figures of merit to compare the efficiencies of several NLO crystals.     

Optical stress sensor based on electro-optic compensation for photoelastic birefringence in a single crystal

An optical stress sensor is proposed by using a single crystal with both electro-optic and photoelastic effects. Different from previous crystal-based stress sensors, the proposed sensor is based on electro-optic compensation for stress-induced birefringence and does not need an additional quarter-wave plate or modulator, because the stress-sensing element is simultaneously used as an electro-optic compensator. Candidate sensing materials include electro-optic crystals of the 3?m symmetry group and all glass with large Kerr coefficients. A primary experiment has demonstrated that the stress-induced birefringence in lithium niobate crystal can be compensated by its electro-optic birefringence. The proposed stress sensor is compact and low cost, and it is possible to achieve closed-loop stress measurement.     

Time-resolved optical transients in tetragonal BaTiO3

We present and analyze the room temperature (T= 23.5 degrees C) time behavior of the transmitted intensities of polarized light passing through an unclamped (100)-type single crystal of barium titanate (BaTiO3) when subject to a time-dependent, externally applied electric field. To the authors' knowledge, this is the first reported observation and analysis of such time-resolved optical transients. According to a previous [J. Opt. Soc. Am. A 22, 377 (2005)] observation by the authors, this original optical technique can, in principle, be used on 18 out of 20 noncentrosymmetric crystal point groups where the first-order (Pockels) and second-order (Kerr) electrooptic effects coexist. Because of its nondestructive nature, this novel optical method would be a useful tool in other fields of condensed-matter physics in which time-behavior observation and characterization of certain physical parameters of crystals are important.     

Efficient polarization converter for projection displays

In the waveguiding limit, a twisted nematic liquid crystal cell behaves as an achromatic polarization rotator. We propose and demonstrate the application of such a polarization rotator to convert unpolarized light into linearly polarized light with almost 100% efficiency. This polarization converter has a 2:1 aspect ratio, which is close to the 16:9 ratio for modern televisions. It can be used therefore in a projection display with polarization-dependent light valves such as a liquid crystal light valve. Both transmittive and reflective light valves can be used. The temperature dependence of the achromatic polarization rotator is also studied.     

Equivalent geometric transformations for spin and orbital angular momentum of light

We consider the analogous geometric transformations for spin and orbital angular momentum states of light. Spin angular momentum is manifested as polarization and its possible transformations are typified by those introduced by waveplates and the rotation associated with optical activity. Orbital angular momentum is associated with the mode structure of the beam and, while the action of a waveplate is similar to that of a mode converter, the equivalent analogue of optical activity is not obvious. We reason that the equivalent is a rotation of the transmitted image. We consider the extent to which an image orientation of this type might be achieved by a coherent fibre bundle, twisted around its central axis. The possibility of equivalents to the Kerr, Pockels and Faraday electro-optic effects for orbital angular momentum is raised.     

Polarization control by use of the electro-optic effect in periodically poled lithium niobate

We propose a method to control the polarization of light by the electro-optic effect in periodically poled lithium niobate. A single integrated chip of Z-cut lithium niobate having two sections is used. The first section is not periodically poled, whereas the second section is. With an electric field applied along the Z axis of the first section and another electric field applied along the Y axis of the second section, light with an arbitrary elliptical polarization can be converted into a fixed linearly polarized state.     

Efficient poling of electro-optic polymers in thin films and silicon slot waveguides by detachable pyroelectric crystals

Pyroelectric crystals are used as a conformal and detachable electric field source to efficiently pole electro-optic (E-O) polymers in both parallel-plate (transverse) and in-plane (quasi-longitudinal) configurations. Large Pockels coefficients in poled thin films and high tunability of resonance wavelength shift in hybrid polymer silicon slot waveguide ring-resonator modulators have been achieved using this method.     

Efficiency of electrooptic spin-to-orbital angular momentum conversion in crystals

We introduce a figure of merit for the photon spin-to-orbital angular momentum conversion via electrooptic (EO) Pockels effect in single crystals. Relations for the effective EO coefficients are derived for different symmetry groups. We show that Bi₁₂TiO₂₀ crystals reveal the highest figure of merit among well studied crystalline EO materials. The efficiency of the spin-to-orbital angular momentum conversion is measured experimentally for a number of single crystals.     

High-Contrast Spatial Light Modulator by use of the Electroabsorption and the Electro-Optic Effects in a GaAs Single Crystal

A new spatial light modulator that uses the electroabsorption and the electro-optic effects in a GaAs single crystal is proposed. The device has the same structure as a Pockels readout optical modulator and can be operated at a frame rate higher than 500 Hz. When the electroabsorption and the electro-optic effects are combined, the dynamic range (contrast ratio) becomes larger than that which results when either effect is used singly. It was experimentally confirmed that the modulator has a high contrast ratio (greater than 2000:1), high sensitivity, and consequently large gamma characteristics.     

双拓扑绝缘体介质界面的反射波极化调控特性

本文对两种三维强拓扑绝缘体分界面的反射极化现象进行了研究,得到了线偏振光完全转化的普适性充要条件.通过分析分界面的直接反射率、交叉反射率以及极化转化率,发现该模型利用现有的拓扑绝缘体材料就可以实现线极化波的完全转变,突破了需要新的较小介电常数的拓扑绝缘体材料才能完全转化的限制.该转化过程可以利用克尔旋转角进行验证,并给...     

The intertwined history of polarimetry and ellipsometry

Ellipsometry and reflection polarimetry are almost synonymous. Therefore it is not surprising that ellipsometry and polarimetry share a common history which is that of optical polarization. The discoveries in the late 1600s by Bartholinus and Huyghens of double refraction by Iceland spar and the unusual properties of the twin beams thus generated presented insurmountable difficulties for the entrenched corpuscular-ray theory of Newton and caused research on polarization to remain stagnant in the 1700s. Major breakthroughs came in the early 1800s when Malus discovered polarization of light by reflection and his cosine-squared law and Fresnel and Arago enunciated their laws of interference of polarized light that helped establish the transverse vector nature of luminous vibrations. Important further research immediately followed on optical rotatory power by Arago, Biot, and Pasteur that ushered fundamental and practical applications of polarimetry in chemistry and biology. Fresnel deserves to be recognized as a founder of ellipsometry by virtue of his laws of reflection of polarized light at interfaces between dissimilar media and his identification and production of circular and elliptical polarization. The later part of the 19th century witnessed significant discoveries of magneto-optic and electro-optic effects by Faraday, Kerr, and Pockels that greatly enriched polarization optics and physics. The 1896 discovery of the Zeeman effect launched the exciting field of solar polarimetry. The 1864 crown achievement of Maxwell's electromagnetic (EM) theory provided a unified framework for the analysis of polarization phenomena across the entire EM spectrum.     

Application of the Jones calculus for a modulated double-refracted light beam propagating in a homogeneous and nondepolarizing electro-optic uniaxial crystal

The Jones matrix calculus is applied to an electro-optic crystal with uniaxial symmetry when the light beam is incident nearly normally on the crystal face. The approach allows one to treat refracted waves and rays that diverge in the crystal and are modulated by an external low-frequency field. The effect of partial interference of overlapping refracted beams is allowed for and calculated for the case of uniform intensity of the beam over its cross section. The method is employed to analyze optical systems containing an imprecisely cut and aligned electro-optic crystal plate.     

Pauli algebraic analysis of polarized light modulation

The modification of the polarization and spectral structure of light by electro-optic modulation with longitudinal effect in crystals of class 42 m is analyzed in the frame of a Pauli algebraic and Poincaré geometric approach. The results are generalized, in a vectorial Pauli algebraic form, for any birefringent time-varying device.     

Analysis of electro-optic crystal-based Fabry-Perot etalons for high-speed spatial light modulators

The use of electro-optic (EO) crystal-based Fabry-Perot modulators (FPMs) as high-speed spatial light modulators is proposed. The FPMs operate with an extremely low drive voltage and a high extinction ratio. It is revealed by analysis of both the linear EO effect and the inverse piezoelectric effect of various EO crystals that three kinds of crystal configuration are suitable as FPMs. One of these is applicable to isotropic crystals, point groups 23 and (-)43m, and the others are better suited for uniaxial EO crystals, point groups (-)42m and 3m. Typical EO crystals suitable as FPMs are ferroelectric crystals such as LiNbO3, LiTaO3, and LiIO3 and sillenite compounds such as Bi12SiO20 and Bi12GeO20 as well as compound semiconductors such as GaAs and GaP.     

Complex modulation using tandem polarization modulators

A novel photonic technique for implementing frequency up-conversion or complex modulation is proposed. The proposed circuit consists of a sandwich of a quarter-wave plate between two polarization modulators, driven, respectively, by an in-phase and quadrature-phase signals. The operation of the circuit is modelled using a transmission matrix method. The theoretical prediction is then validated by simulation using an industry-standard software tool. The intrinsic conversion efficiency of the architecture is improved by 6 dB over a functionally equivalent design based on dual parallel Mach–Zehnder modulators. Non-ideal scenarios such as imperfect alignment of the optical components and power imbalances and phase errors in the electric drive signals are also analysed. As light travels, along one physical path, the proposed design can be implemented using discrete components with greater control of relative optical path length differences. The circuit can further be integrated in any material platform that offers electro-optic polarization modulators.     

Polarization conversion in conical diffraction by metallic and dielectric subwavelength gratings

Subwavelength metallic and dielectric diffraction gratings which rotate the linear polarization of incident light by 90 degrees are examined. Using rigorous diffraction theory in total-internal-reflection configuration, it is shown that full conversion from incident transverse electric field to transverse magnetic zero-order field can be achieved with both dielectric and metallic elements, but dielectric gratings provide higher efficiency and are thus preferable. The fabrication aspects and constraints are discussed in detail and the behavior of the gratings over broad wavelength bands is presented.