Enhanced polarization conversion for an anisotropic thin film

This work presents an explicit expression for the reflection and transmission coefficients of an anisotropic thin film in the general case in which the optical axis and the incident ray are arbitrarily directed in three dimensions. The polarization conversion quantities for reflected light from an anisotropic thin film are calculated and analyzed for two three-layered systems. With light incident from a dense medium, polarization conversion will be enhanced at a particular incident angle that exceeds the critical angle.     

Reflection of light from an anisotropic film on an anisotropic substrate

The ellipsometric equations are presented for a reflecting film system consisting of an anisotropic layer and an anisotropic substrate with the principal axes of the dielectric tensor in the plane of incidence of the sample. Linear Drude approximations are obtained for the angular dependences of the ellipsometric parameters.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 102–107, May, 1991.     

Fluctuations of the polarization state of laser light

The instantaneous polarization of a laser fluctuates between different elliptical states resulting in a partial polarization. The fluctuations are calculated for a laser with partial linear polarization from the known statistical distributions of the amplitude and phase of laser light. A mean square deviation of the polarization direction of 5 s of arc results for a typical He-Ne-laser.     

Fluctuations of the polarization state of laser light

The instantaneous polarization of a laser fluctuates between different elliptical states resulting in a partial polarization. The fluctuations are calculated for a laser with partial linear polarization from the known statistical distributions of the amplitude and phase of laser light. A mean square deviation of the polarization direction of 5 s of arc results for a typical He-Ne-laser.     

Birefringence measurements of MnPc thin film by polarization microscopy

We have studied optical properties of near-infrared (NIR) spectra and birefringence of the manganese phthalocyanine (MnPc) thin films. The morphology of the MnPc thin film grown on KCl (0 0 1) substrates was observed by using an atomic force microscope. The NIR spectral range of 1.0-1.7 μm was studied in this study, because that of 1.3-1.5 μm is known as an optical communication wavelength. The birefringence was measured with changing the growth condition of a deposition rate and a substrate temperature. The birefringence of the film was most affected by the deposition rate.     

Reflection and absorption of light by a thin semiconductor film

Optics and Spectroscopy - Reflection and absorption of light by a thin semiconductor film are investigated using the local field method taking into account local field inhomogeneities. The...     

Novel orbital ordering induced by anisotropic stress in a manganite thin film

A novel structure of orbital ordering is found in a Nd0.5Sr0.5MnO3 thin film, which exhibits a clear first-order transition, by synchrotron x-ray diffraction measurements. Lattice parameters vary drastically at the metal-insulator transition at 170 K (= T(MI)), and superlattice reflections appear below 140 K (= T(CO)). The electronic structure between T(MI) and T(CO) is identified as A-type antiferromagnetic with a d(x2-y2) ferro-orbital ordering. The new type of antiferro-orbital ordering characterized by the wave vector (1/4 1/4 1/2) in cubic notation emerges below T(CO). The accommodation of the large lattice distortion at the first-order phase transition and the appearance of the novel orbital ordering are brought about by the anisotropy in the substrate, a new parameter for the phase control.     

Buckling of a stiff thin film on a compliant substrate under anisotropic biaxial prestrain

The structure of stretchable electronics is based on the buckling of a thin film on a compliant substrate. Under anisotropic biaxial prestrains, this structure may buckle into several patterns, including cylindrical, checkerboard, and undulating patterns. The displacement and energy of each pattern are deduced analytically. By comparing their minimum potential energies, the critical buckling condition of each pattern is determined. After secondary bifurcation, the checkerboard pattern occurs just above the critical prestrains, but the undulating pattern dominates other regions. The buckling amplitude and wavenumber of the undulating pattern are shown under biaxial prestrains. Even if the structure is under equi-biaxial prestrains, it may buckle into an asymmetric undulating pattern.     

Control of polarization deviation at two separate wavelength by using all dielectric thin film materials

Two separate wavelength 1315 nm and 1550 nm were most widely used in near-infrared spectrum region. Based on a four-layer structure and a symmetry structure, a initial thin film stack system was constructed. Then it was optimized alternately by simplex and conjugate graduate algorithm, a beam splitter with splitting ratio R:T = 50:50 at this two wavelength was gained. The design result showed that the difference between reflectivity of P and S light around wavlength range 1300?1330 nm and 1535?1565 nm at incident angle 40°?50° was all below 2%. That indicated our design controlled the polarization deviation well at two separate wavelength with a reasonable range for both wavelength and incident angle.     

Resonant interaction of light with a thin film of three-level atoms

Refraction of a double-frequency optical pulse at the interface between two linear dielectrics containing a thin film of resonant atoms is considered. The dynamics of the system is treated based on the model of three-level atoms with the V-type energy diagram. Refraction of short and long (compared with the Rabi oscillation period) pulses is analyzed with allowance for local-field effects. In both cases, the shape of the pulse corresponding to one carrier wave frequency is shown to depend on the energy of the pulse with the other carrier wave frequency. In particular, both the frequency and the depth of the amplitude modulation arising in the refracted pulse are changed.     

Control the polarization state of light with symmetry-broken metallic metastructures

Controlling the polarization state, the transmission direction, the amplitude and the phase of light in a very limited space is essential for the development of on-chip photonics. Over the past decades, numerous sub-wavelength metallic microstructures have been proposed and fabricated to fulfill these demands. In this article, we review our efforts in achieving negative refractive index, controlling the polarization state, and tuning the amplitude of light with two-dimensional (2D) and three-dimensional (3D) microstructures. We designed an assembly of stacked metallic U-shaped resonators that allow achieving negative refraction for pure magnetic and electric responses respectively at the same frequency by selecting the polarization of incident light. Based on this, we tune the permittivity and permeability of the structure, and achieve negative refractive index. Further, by control the excitation and radiation of surface electric current on a number of 2D and 3D asymmetric metallic metastructures, we are able to control the polarization state of light. It is also demonstrated that with a stereostructured metal film, the whole metal surfaces can be used to construct either polarization-sensitive or polarization-insensitive prefect absorbers, with the advantage of efficient heat dissipation and electric conductivity. Our practice shows that metamaterials, including metasurface, indeed help to master light in nanoscale, and are promising in the development of new generation of photonics.     

Stokes eigenvectors and evolution of the polarization of light in an anisotropic medium

The problem of evolution of the Stokes vector of a wave upon its transmission through an arbitrary homogeneous anisotropic medium with a non-Hermitian dielectric tensor has been solved in the general form. Explicit expressions for the Stokes vectors of eigenwaves have been obtained.     

Effect of epitaxial strain on the spontaneous polarization of thin film ferroelectrics

Epitaxial strain can substantially enhance the spontaneous polarizations and Curie temperatures of ferroelectric thin films compared to the corresponding bulk materials. In this Letter we use first principles calculations to calculate the effect of epitaxial strain on the spontaneous polarization of the ferroelectrics , , and , and the multiferroic material . We show that the epitaxial strain dependence of the polarization varies considerably for the different systems, and in some cases is, in fact, very small. We discuss possible reasons for this different behavior and show that the effect of epitaxial strain can easily be understood in terms of the piezoelectric and elastic constants of the unstrained materials. Our results provide a computational tool for the quantitative prediction of strain behavior in ferroelectric thin films.     

Nonlinear diffraction due to the transient polarization in a thin film of atomic gases*

Nonlinear optical response of a thin layer of rarefied atomic vapor is examined by taking into account the atomic motion as well as collisions with the cell walls. Extraordinary pattern of self-diffraction spectrum due to the transient polarization is predicted. It is shown that the spectra are Doppler free and depend strongly upon the vapor thickness. A new possibility of signal enhancement is revealed and a simple device is suggested to enhance greatly the nonlinear reflection signal from a resonant vapor layer. Received: 3 July 1997/Accepted: 5 December 1997     

Macroscopic pure state of light free of polarization noise

The preparation of completely nonpolarized light is seemingly easy; an everyday example is sunlight. The task is much more difficult if light has to be in a pure quantum state, as required by most quantum-technology applications. The pure quantum states of light obtained so far are either polarized or, in rare cases, manifest hidden polarization; even if their intensities are invariant to polarization transformations, higher-order moments are not. We experimentally demonstrate the preparation of the macroscopic singlet Bell state, which is pure, is completely nonpolarized, and has no polarization noise. Simultaneous fluctuation suppression in three Stokes observables below the shot-noise limit is demonstrated, opening perspectives for noiseless polarization measurements. The state is shown to be invariant to polarization transformations. This robust highly entangled isotropic state promises to fuel important applications in photonic quantum technologies.     

Controllable snail-paced light in biological bacteriorhodopsin thin film

We observe that the group velocity of light is reduced to an extremely low value of 0.091 mm/s in a biological thin film of bacteriorhodopsin at room temperature. By exploiting unique features of a flexible photoisomerization process for coherent population oscillation, the velocity is all-optically controlled over an enormous span, from snail-paced to normal light speed, with no need of modifying the characteristics of the incident pulse. Because of the large quantum yield for the photoreaction in this biochemical system, the ultraslow light is observed even at low light levels of microwatts, indicating high energy efficiency.     

Shape of the magnetic resonance line in a thin film on the surface of an anisotropic superconductor

The shape of the EPR line in a thin (=λ/2, where λ is the London penetration depth of the magnetic field in the superconductor) paramagnetic film deposited on the surface of an anisotropic superconductor is calculated in an oblique magnetic field with allowance for the inhomogeneity of the local magnetic field of the Abrikosov vortex lattice. It is shown that, as the tilt angle of the external magnetic field is varied, the shape of the EPR line changes noticeably. This fact can give additional information about the superconductor parameters (the symmetry type of the vortex lattice and the anisotropy parameter of the superconductor). Fiz. Tverd. Tela (St. Petersburg) 41, 386–388 (March 1999)     

Instrument for determining the polarization state of reflected and transmitted light

An instrument is described which enables the state of polarization of a light beam to be found. It is discussed with reference to studies of optical rotation, circular dichroism and conventional ellipsometry. The main features are that it records automatically and allows the azimuth and ellipticity of an elliptically polarized beam to be measured simultaneously over a wide wavelength range. The performance is illustrated by spectra showing the optical rotation and circular dichroism of an octahedral cobalt lll species.     

Modulation spectroscopy using the beam-foil light source

When a beam of ions passes through a thin exciter foil, certain radiation emitted by the beam particles can exhibit time-periodic intensity variations. These variations can be induced by external E and H fields, or they can be the result of the field-free atomic structure itself.Intensity modulations observed so far in beam-foil spectroscopy can be divided into three classes: (1) Quantum mechanical interference of fine structure levels. This is a QM resonance arising from time-dependent populations of emitting states having different transition probabilities. The resonance is induced by external constant electric fields. (2) Initial coherent superpositions of radiating states. This results from the creation of M_L alignment at the instant of excitation by the foil. The modulations are field free and are observed in polarized light. (3) Rotating electric dipole in a magnetic field. When alignment occurs, the intensity of the beam radiation after excitation satisfies the relation I(t) = = I₀[1+Acos(2γHt)] e^?αt. The modulation will be a function of the magnetic field H and the gyromagnetic ratio γ.These effects can be used to study Lamb shifts, g-values, fine structure levels, and interaction processes.