Multilayer Polarizers Research Articles

In-line extreme ultraviolet polarizer with hybrid configuration

A novel hybrid Au-multilayer-Au in-line extreme ultraviolet (EUV) optical polarizer is presented in this paper. Different from all-Mo/Si multilayer EUV polarizer, this polarizer is based on the concept that Au surfaces work as reflecting elements for in-line optics routine, while polarization effect is realized by polarizing multilayer. Simulation shows that the proposed polarizer with 80 degrees-70 degrees-80 degrees angle configuration has about 30% of transmission and 12 eV of bandwidth half maximum, which enables more throughput and broader bandwidth than the all-multilayer one.

Design of transmission multilayer polarizer for soft X-ray using a merit function

A new method of designing soft X-ray transmission multilayer polarizer for use at a single wavelength using a merit function has been eveloped. A merit function of product of p-transmittance throughput and logarithm of transmittance polarization ratio was chosen. Characteristics of Mo/Si multilayer calculated using the merit function at 13.0 nm have been compared with those calculated using the traditional method by the present authors and those reported so far. The merit function has given the most optimal results of throughput of 30.0% and polarization ratio of 202. The polarizers of much higher polarization ratio or much larger p-transmittance can be designed by choosing the number of layers and optimizing the thickness of each layer to maximize the merit function. Using this method, the roughness effect has been studied on Mo/Si and La/B multilayer polarizers at 13.0 nm and 6.7 nm, respectively. It was found that the influence of roughness is crucial in shorter wavelength region.

Multilayer polarization elements and their applications to polarimetric studies in vacuum ultraviolet and soft X-ray regions

Multilayer polarization elements and their applications to polarimetric studies in 20–400 eV region are mainly reviewed. General principle of selecting material combinations to get high linear polarizance multilayers of reflection type is given with practical examples, with periodic or non-periodic layer structures depending on the usage. Transmission type is introduced as linear polarizer and phase shifter. Their applications include polarization diagnosis of laboratory optical systems and synchrotron radiation beamlines of linear and circular polarization, magnetic rotation experiments such as Faraday rotation and magnetic Kerr rotation on magnetic films and multilayers, and ellipsometry to measure optical constants of thin films precisely. Polarization analysis of soft X-ray fluorescence using multilayer-coated grating is also mentioned. Finally this review is summarized with outlook of further developments.

Soft X-ray magmeto-optical Faraday rotation measurements with the multilayer polarizer

We measured magneto-optical (MO) Faraday rotation around the M2,3 edges (60—70 eV) of Ni film on 3W1B beam line of Beijing Synchrotron Radiation Facility (BSRF) in the soft X-ray region through a versatile polarimeter with mutilayer polarizers, which is mainly composed of polarizer, analyzer, sample frame, round NdFeB permanent-magnet and MCP detector. We used the reflective aperiodic molybdenum/silicon broadband multilayer polarizers as the polarizer and the analyzer in the versatile polarimeter, and obtained a series of Faraday rotation results in the 60—70 eV region. The results demonstrate that the Faraday rotation angles are obviously large around Ni M2,3 edges, the rotation angles are 179±019°(average rotation angle in parallel and antiparallel magnet fields) and -076±009°(average rotation angle in parallel and antiparallel magnet fields) at the energy 655 eV and 68 eV, respectively.

Multilayer polymeric mode and polarization filters for integrated optics

We demonstrate theoretically as well as experimentally that a four-layer polymeric waveguide structure can be used to produce a mode and a polarization filter. Various optical properties such as refractive index, birefringence and propagation constant of polycarbonate, polystyrene and a commercially available photoresist (from Shipley) are presented. The thin film structures consisting of glass/polycarbonate/polystyrene/air are used for demonstrating polarization filter action and glass/photoresist/polystyrene/air structure for mode filter. Expressions for the electric field intensity spatial distribution for the structure are used to calculate the intensity profiles to support the observed behavior. The experimental values were in good agreement with the one obtained theoretically.

Non-Hermitian polarizers: a biorthogonal analysis

The non-Hermitian operators of the ideal nonorthogonal multilayer optical polarizers are spectrally analyzed in the framework of skew-angular biorthonormal vector bases. It is shown that these polarizers correspond to skew projectors and their operators are generated by skew projectors, exactly as the canonical ideal polarizers correspond to Hermitian projectors. Thus the common feature of all the polarizers (Hermitian and non-Hermitian) is that their "nuclei" are (orthogonal or skew) projectors--the generating projectors. It is shown that if these nonorthogonal polarizers are looked upon as variable devices, two kinds of degeneracy may occur for suitable values of the inner parameter of the device: The corresponding operators may become normal (more precisely, Hermitian) or, on the contrary, very pathological--defective and singular. In the first case their eigenvectors and biorthogonal conjugate eigenvectors collapse into a unique pair of eigenvectors; in the second case their eigenvectors (as well as their biorthogonal conjugates) collapse into a single vector.

Broadband multilayer polarizers for the extreme ultraviolet

Nonperiodic molybdenum/silicon broadband multilayer polarizers have been designed using numerical optimization algorithm and fabricated using direct current magnetron sputtering. Their performances have been characterized using the high precision eight-axis soft x-ray polarimeter at the BESSY facility. Different multilayers have measured s-polarized reflectivities of 27% at 13.1nm and higher than 15% over the wavelength range of 13–19nm. Nearly constant s reflectivity, up to 37%, is observed over the 15–17nm wavelength range, where the degree of polarization is more than 98%. Furthermore, these multilayer polarizers also show high s reflectivity and polarization over a broad angular range at fixed wavelength.

45.1: Invited Paper: Advanced Polarizer Film for Improved Performance of Liquid Crystal Displays

A multilayer birefringent reflective polarizer film is described. This film has high refractive index difference between the birefringent and isotropic layers in the stretch direction and substantially matched indices in the remaining orthogonal axes. The film has high polarizing efficiency, excellent color uniformity and is thinner than conventional reflective polarizers.

Magnetic rotation spectra of Co/Pt and Co/Cu multilayers in 50–90 eV region

Faraday rotation spectra of Co/Pt multilayers were obtained in the region including Co M 2,3 and Pt N 6,7 absorption edges by using multilayer polarizers, and were transformed to magnetic circular dichroism (MCD) spectra by Kramers–Krönig analysis (KKA). From the dependence of the rotation angle on the layer thickness, it was suggested that the magnetization of Co tends to be uniform in Co layers and that of Pt is localized at Co/Pt interfaces. The orbital magnetic moment of Co was estimated to be about 0.17 μ B /Co. The similarity of electronic states around magnetized Pt site between Co/Pt multilayers and CoPt 3 alloy is suggested by the resemblance of the MCD spectra of both materials around Pt N 6,7 edges. In addition, magnetic Kerr rotation of Co/Cu multilayer was measured and was observed around Co M 2,3 and Cu M 2,3 absorption edges.

Theoretical study of polymeric metal clad optical waveguide polarizer

Planar optical waveguides consisting of thin dielectric films and buffer layers with metal cladding have been investigated theoretically. A computer program was written to calculate the exact zeroes of complex eigenvalue equation for TE and TM modes in multilayer metal clad waveguide polarizer. Numerical results and illustrations are given for Polycarbonate waveguide with other polymers as buffer and Al, Ag and Au as cladding metals at 0.6238 μ m . It is also shown that, using thin (finite) films of metal produce more efficient polarizers as compared to semi-infinite metal films. Effect of low index buffer layer on attenuation of TM/TE modes is also investigated.

Polarization measurements of laboratory VUV light: a first comparison between multilayer polarizers and photoelectron angular distributions

The use of photoelectron angular distributions to determine the linear polarization of VUV light over a wide range of photon energies is demonstrated. Light at wavelengths from 256 to 736 Å, partially polarized by large angle reflections in a toroidal grating monochromator and at a refocus mirror, has been analyzed. The results are validated by comparison measurements at spot wavelengths using multilayer polarizers.

A Very Cold Neutron Reflectometer for MIRA at the FRM-II

MIRA is a beam line for very cold neutrons (7.7 Å < λ < 30 Å) at the new FRM-II reactor. It can be operated as a classical reflectometer, working in the θ−2θ scan mode and a horizontal reflection geometry with q-transfers of 7.0 × 10-4 Å-1 < q < 1.1 Å-1. A flux of 2.0 × 106 neutrons /(cm2 s) at the sample is aimed for. We also plan to use a multilayer polarizer and an analyzer to perform polarized neutron reflectometry. Furthermore, the instrument will be used for the development of new techniques.

MULTILAYER POLARIZERS FOR THE USE OF He-I AND He-II RESONANCE LINES

Multilayer polarizers for the use of He resonance lines have been developed. Si/Mg and SiC/Mg multilayers were designed and fabricated for the He-I and He-II resonance lines, respectively. The performance was checked by the use of synchrotron radiation. The polarizance and s-reflectance of the He-II polarizer measured at an angle of incidence of 40° were 0.98 and 41%, respectively. The polarizance of the He-I polarizer measured at an angle of incidence of 31.5° was 0.96.

Design of ultra‐wideband multilayer slant linear polarizer using a genetic algorithm

AbstractIn this letter, for the first time, a genetic algorithm is applied successfully for the design and optimization of a multilayer slant linear polarizer to cover a bandwidth of 1:18. In the algorithm, the fitness function is selected based on the return‐loss requirement. A minimum of 10 dB return loss in the specified bandwidth was achieved. © 2001 John Wiley &amp; Sons, Inc. Microwave Opt Technol Lett 30: 119–122, 2001.

Analysis of multilayer infinite periodic array structures with different periodicities and axes orientations

This paper presents a general procedure to analyze a multilayer array structure, where each layer may have different periodicities, different lattice structures, and/or the array axes between the layers may be nonparallel. The procedure involves the determination of a global cell with a global coordinate system, then computations of local generalized scattering matrices (GSMs) of individual layers followed by modal mapping from local to global GSMs. The global GSMs for individual layers are then combined to characterize the entire structure. The mapping relations are derived for two layers with different lattice structures, different periodicities, and array-axes orientations. Three examples of practical importance are considered to demonstrate the methodology. The first example is a two-layered patch array with different periodicities. The second example is an array of subarrays with several patch elements within a subarray. It is shown that a subarray can be characterized rigorously by characterizing only one element of a subarray instead of analyzing all the elements of the subarray simultaneously. Consequently, the analytical and computational complexities reduce considerably. The last example is a patch array loaded with a multilayer meander-line polarizer. The patch array and the meander-line array have two different periodicities and the axes are nonparallel. Detailed radiation characteristics of the structure are presented and compared with that of a strip-grid polarizer. The computational advantages of this method are discussed.

Transmission multilayer polarizers for use in the 55-90 eV region.

Free-standing Al/YB(6) and Mo/Si transmission multilayer polarizers have been developed for use in the photon energy regions 55-72 eV and 72-90 eV, respectively, to improve the degree of polarization of synchrotron radiation light from beamline monochromators. The polarizance (polarizing ability) and transmittance of the Al/YB(6) multilayer for unpolarized light at 64 eV were 77% and 3.4%, respectively, and the polarizance and transmittance of the Mo/Si multilayer at 80 eV were 79% and 2.2%, respectively. By using the Mo/Si polarizer, the degree of polarization of the monochromated light at BL8B1 of UVSOR was increased from 95 to 99% in the 78-84 eV region.

A simple accurate method of alignment of beamline optics with the use of EUV multilayer polarizers.

A simple alignment method is proposed, which enables the alignment of beamline optics of a bending section accurately, relying on the linear state of polarization of synchrotron orbital radiation rather than the beam intensity. The method utilizes extreme UV (EUV) multilayers as a compact polarization monitor detecting unwanted vertical polarization components. The proposed method was found to be far more sensitive than that relying on the maximum intensity. Another advantage is the insensitivity to surface contamination, such as an irradiation mark on the mirror degrading reflectance. A design example is presented for use around a photon energy of 370 eV along with an experimental example at a photon energy of 97 eV.

Ellipsometry in the extreme ultraviolet region with multilayer polarizers

The sensitivity of ellipsometry to bulk surfaces and thin films in the extreme ultraviolet region is studied theoretically in reference to the complex refractive indices of the materials and the extinction ratio of a multilayer polarizer. At a photon energy of 97 eV, which is 12.8 nm in wavelength, sensitivities in terms of the minimum detectable differences to a refractive index of 0.027 and to an extinction coefficient of 0.048 can be expected for bulk surfaces. For a thin film sample, the sensitivities are 10 −3 nm for the thickness, 10 −4 for the refractive index and 10 −5 for the extinction coefficient. Ellipsometry in this wavelength region proves to be useful for the study of the near-surface region of the sample within a penetration depth of approximately 150 nm with good material and optical structure sensitivity.

Analysis of multilayered meander line polarizer

In this paper, we present an analysis of a multilayered meander line polarizer. Using waveguide modal fields and Galerkin's method of moments, the equivalent susceptance of a meander line screen is determined. The equivalent susceptance includes the effect of the dielectric layers that are present in the close vicinity of the meander line plane. The transmission matrix formulation then is invoked to find the transmission and reflection behavior of a multilayered meander line structure. Numerical results for equivalent susceptance, return loss, and axial ratio are found to compare well with the measured data. Performance characteristics of multilayered meander line polarizers are studied, and the results are presented. © 1997 John Wiley & Sons, Inc. Int J Microwave Millimeter-Wave CAE 7: 442–454, 1997.

Soft X-Ray Optics. The Forefront of Soft X-Ray Multilayer Polarizers and Their Applications.

With use of synthetic microstructures as a mirror, multilayer polarizers have been developed for control and measurement of polarization in the soft x-ray region. The same structures made into free-standing transmission elements, showed good polarization performance. These new polarizing elements are evaluated in refering to the measured data. Some examples of forefront application of the polarizing elements are reviewed.