Mirror Layer Research Articles

Interface study of a high-performance W/B4C X-ray mirror

A high-performance W/B4C multilayer mirror with 80 periods of nominally 1.37 nm was measured by grazing-incidence small-angle X ray scattering (GISAXS) in order to analyse the lateral and vertical correlations of the interface roughness within the framework of a scaling concept of multilayer growth. A dynamic growth exponentz= 2.19 (7) was derived, which is close to the value predicted by the Edwards–Wilkinson growth model. The effective number of correlated periods indicates a partial replication of the low interface roughness frequencies. A simulation of the GISAXS pattern based on the Born approximation suggests a zero Hurst fractal parameterHand a logarithmic type of autocorrelation function. The as-deposited mirror layers are amorphous and exhibit excellent thermal stability up to 1248 K in a 120 s rapid thermal vacuum annealing process. At higher temperatures, the B4C layers decompose and poorly developed crystallites of a boron-rich W–B hexagonal phase are formed, and yet multilayer collapse is not complete even at 1273 K. Ozone treatment for 3000 s in a reactor with an ozone concentration of 150 mg m−3results in the formation of an oxidized near-surface region of a thickness approaching ∼10% of the total multilayer thickness, with a tendency to saturation.

Optical sensing and determination of complex reflection coefficients of plasmonic structures using transmission interferometric plasmonic sensor

The combination of interferometry and plasmonic structure, which consists of gold nanoparticle layer, sputter coated silicon oxide spacer layer, and aluminum mirror layer, was studied in transmission mode for biosensing and refractive index sensing applications. Because of the interferometric nature of the system, the information of the reflection amplitude and phase of the plasmonic layer can be deduced from one spectrum. The modulation amplitude in the transmission spectrum, caused by the interference between the plasmonic particle layer and the mirror layer, increases upon the refractive index increase around the plasmonic particles due to their coherent backscattering property. Our proposed evaluation method requires only two light sources with different wavelengths for a stable self-referenced signal, which can be easily and precisely tuned by a transparent spacer layer thickness. Unlike the standard localized surface plasmon sensors, where a sharp resonance peak is essential, a broad band plasmon resonance is accepted in this method. This leads to large fabrication tolerance of the plasmonic structures. We investigated bulk and adsorption layer sensitivities both experimentally and by simulation. The highest sensitivity wavelength corresponded to the resonance of the plasmonic particles, but useful signals are produced in a much broader spectral range. Analysis of a single transmission spectrum allowed us to access the wavelength-dependent complex reflection coefficient of the plasmonic particle layer, which confirmed the reflection amplitude increase in the plasmonic particle layer upon molecular adsorption.

Detection and Identification of the Latent Microorganisms in the Altered Layers of Ancient Bronze Mirrors

We obtained ancient bronze mirrors and carried out: scanning electron microscopy (SEM) of fractured altered layers; biologic microscopic observation of Gram-stained samples; and DNA analyses of samples removed from altered sites. Fine particles about 2 mm in length were confirmed in the altered layer by SEM. Microorganisms of identical size were observed in the Gram-stained sample removed from the altered layer through a biologic microscope. Fine particles observed under SEM were considered to be microorganisms. Many fine particles were confirmed, particularly in the altered sites, by SEM. Certain types of microorganisms may have played a part in the alteration (deterioration) of the ancient bronze mirrors while the latter were buried in soil. From the base sequences obtained by DGGE analysis, two types of microorganisms were present in the altered layer of the mirror. One was 94.7% homologous to the 16S rDNA of the uncultured bacterium (accession number: AY 053488). It was also highly homologous to the sequence derived from the 16S rDNA of the Xanthomonadaceae family (e.g., Stenotrophomonas, Xanthomona). That is, the sequence was derived from a strain belonging to the Xanthomonadaceae family. The other base sequence was 97.4% homologous to the 16S rDNA of the Bacteroidales order such as uncultured Bacteroidales bacterium (accession number: AY 859647). That is, the sequence was derived from a strain belonging to the Bacteroidales order. Genes of microorganisms, presumed to belong to the Acetobacter and Gluconacetobacter genera and the Fe(III)-reducing bacterium, Shewanella algae, were detected from base sequence analysis by cloning. Microbial activity around the mirrors was assumed to be high. The alteration containing corrosion mechanism of bronze mirrors appears complex, but several types of microbes that possibly altered the bronze mirrors were verified. [doi:10.2320/matertrans.MRA2008400]

Wavelength-Selective Polarizer Prepared by Using Glancing Angle Deposition

In this paper, the optical and the structural properties of a wavelength-selective polarizer made of narrow band pass lters (NBPFs) are presented. Anisotropic spacer layers were deposited in the NBPFs by using electron beam evaporation with a glancing angle deposition (GLAD) technique while mirror layers were deposited by a conventional evaporation method. TiO2, Ta2O5 and ZrO2 lms deposited by the GLAD technique at various oblique incident angles were investigated to select the right material for the spacer layer. The e ects of TiO2 spacer layers with tilted, zigzag and helical structures on the wavelength-selective polarizer were also investigated. It is found that the maximum transmittance peak of the wavelength-selective polarizer with TiO2 zigzag spacer deposited by the GLAD technique is separated by 6 nm due to its birefringence.

Characterisation of baroque tin amalgam mirrors of the historical Green Vault in Dresden

The historical Green Vault, one of Europe’s most sumptuous treasure chambers, has reopened in September 2006 in the Dresden Royal Palace. For the baroque presentation of the artworks the special properties of tin amalgam mirrors are of great importance. A comprehensive analytic characterisation was necessary for restoration and reconstruction. The different original casting glasses were analysed in respect of chemical composition, roughness, waviness and optical properties like chromaticity coordinates and transmittance. The microstructure of the tin amalgam layers were investigated on metallographic cross-sections and by X-ray diffraction. The investigations reveal that the tin amalgam layers are composed of γ-HgSn6-10 phase with a grain size between 5 and 50 μm surrounded by a thin mercury phase with about 2 wt. % tin. However the most important property of the baroque tin amalgam mirrors is a relative low reflectivity of about 59% which is drastically lower than for silver mirrors with a reflectivity of about 96%. According to the characterisation results a suitable glass for reconstruction was selected. The mirror layers were produced by historical tin amalgam technology for the rooms not destroyed by bombarding of Dresden in February 1945. For the completely destroyed Jewel Room pure tin layers were deposited by magnetron sputtering. The results show that this new technology enables an adequate substitute for the original tin amalgam layers.

Amorphous <inline-formula><math display="inline" overflow="scroll"><mrow><mi>TiAl</mi></mrow></math></inline-formula> films for micromirror arrays with stable analog deflection integrated on complementary metal oxide semiconductors

Large micromechanical mirror arrays (MMA) with analog pixel deflection integrated onto active CMOS address circuitry require both high-quality planar reflective optical surfaces and a stable deflection versus voltage characteristic. However, for implementing a CMOS-compatible surface-micromachining process, certain obstacles such as a restricted thermal budget and a limited selection of suitable materials must be overcome. Amorphous TiAl is presented as a new actuator material for monolithical MEMS integration onto CMOS circuitry. TiAl films may be sputter deposited at room temperature, have an x-ray amorphous structure, and a low stress gradient. The glassy structure and high melting point make TiAl less vulnerable to stress relaxation, which makes TiAl an ideal spring material. One-level actuators with TiAl or Al-TiAl-Al structural layers and two-level actuators with separate TiAl spring and Al-alloy mirror layers were fabricated and tested with respect to their drift stability. The stability of TiAl-based actuators was found to be superior in comparison to one-level Al-alloy actuators. Two-level actuators with TiAl hinges emerge as the most promising design.

Theoretical Analysis of Voltage-Driven MOSLM with 1-D Magneto Photonic Crystal

The magneto-optic spatial light modulator (MOSLM) can modulate amplitude, phase, and polarization of optical wave front at high speed. However, past MOSLM requires large driving current. To overcome the disadvantage, we have developed the MOSLM with PZT layer driven by electric field and external magnetic field. The effective structure of the voltage-driven MOSLM was also investigated using finite element simulation. A magneto photonic crystal(MPC), which consists of dielectric mirror and magnetic defect layer, can largely enhance MO effect. The stress distribution calculation of MPC structure with good stress distribution and a large Faraday rotation was done based on a structure of a thin MO film.

Temperature behaviour of top mirror reflection spectrum in intra-cavity-contacted oxide-confined vertical-cavity surface-emitting lasers

The thermal dependence of mirror reflective properties in oxide-confined vertical-cavity surface-emitting lasers is investigated. The temperature distribution over a cavity versus applied current is then calculated. The refractive indexes of the mirror layers are subsequently redefined using the temperature coefficients, and changes in radial reflectance spectra of the mirror are analysed. Results show a shift of stop-band and Bragg wavelengths of the mirror, as well as a shift of laser operation wavelength at different injection currents and the formation of a temperature lens in the mirror due to a decrease in temperature close to the edge of the oxide windows.

An Iterative Model for the Steady-State Current Distribution in Oxide-Confined VCSELs

This paper presents an iterative model for the analysis of the current distribution in vertical-cavity surface-emitting lasers (VCSELs) using a SPICE-like approach. The model includes a degeneracy correction for operation at and above threshold. The effect of the resistance due to the p-distributed Bragg reflector (p-DBR) mirror layers and the oxide layer on performance is investigated. Higher sheet resistance under the oxide layer reduces the threshold current, but reduces the current range over which single transverse mode operation occurs. The voltage drop across the p-DBR region dominates spatial hole burning, which is moderated by lateral drift and diffusion. This simple iterative model is applied to commercially available oxide-confined VCSELs.

Holographic Information Storage System: Today and Future

Holographic information storage systems using Collinear Technologies is proposed by Optware Corporation, Yokohama, Kanagawa, Japan, and in which the information and reference beams are modulated coaxially by the same spatial light modulator (SLM). With this unique configuration, the optical pickup can be designed as small as the DVDs and can be placed on one side of the recording disk. In a Holographic Versatile Disc (HVD) structure, the preformatted metadata reflective layer is used for the focus/tracking servo and reading address information, and the dichroic mirror layer is used for detecting holographic recording information without interfering with the preformatted information. A two-dimensional (2-D) digital page data format is used, and the shift-multiplexing method is employed to increased recording density of HVD. Experimental and theoretical studies suggest that the holographic material is very effective to increased recording density of the system. As the servo technology is being introduced to control the objective lens to be maintained precisely to the disk in the recording and the reconstructing process, a vibration isolator is no longer necessary. HVD will be compatible with existing disk storage systems, like CD and DVD, and enable us to expand its applications into other optical information storage systems

Role of granular structure in metal layers on the optical properties of absorbing mirrors

Absorbing mirrors are optical thin film systems consisting of an absorbing metal layer held by a transparent interlayer in defined distance to a (metal) mirror layer. In the reflected light, such three-layer systems show vivid color effects due to the absorption in the metal. This absorption is modified and enhanced by interference effects. The interference condition can be tuned by the thickness of the transparent interlayer. We show by experimentation and by stratified medium model calculations the importance of a nanoscale granular structure in the absorbing metal layer for obtaining a wide spectral range of the color effect.

Highly efficient epitaxial Bragg mirrors with broad omnidirectional reflectance bands in the midinfrared

Laser-quality low-loss epitaxial Bragg mirrors exhibiting a broad omnidirectional stop band in the midinfrared at wavelengths around 7μm are presented. The mirror layers, composed of PbTe and EuTe, exhibit a high refractive index contrast of 80%. Thus, with only three layer pairs, reflectances higher than 99% are achieved for angles of incidence up to 40° and higher than 98% for angles of incidence up to 60°. The angle dependence of the reflectance is accurately determined by analyzing the width of the cavity resonance in a half-wavelength microcavity, formed by two such Bragg mirrors. The experimentally determined omnidirectional stop bandwidth is as high as 50% of the target wavelength. The results are in good agreement to analytical calculations based on the transfer matrix method.

Thermal deflections in multilayer microstructures and athermalization

Exact and approximate analytical solutions are developed for calculating the thermally induced deformation of three-layer cantilever structures. The solution is derived from the closed-form solutions for multilayer films. Thermal deformation and athermalization conditions are derived using dimensionless parameters for film to substrate thickness ratios for three-layer structures. The analytical solution for a narrow beam is applied to a scan mirror plate suspended with two torsional flexures. The results agreed well with finite element method simulations and experiments. Tests are performed using a bulk-micromachined silicon microelectromechanical system scanner that has a thin gold (Au) coil layer on one side and an aluminum (Al) mirror layer on the other side. Useful figures using film-to-substrate thickness ratios and the material independent normalized parameters are introduced for easy thermal deformation computations and performance trades for three-layer structures.

Optical properties of Ba 0.75Al 11O 17.25–BaMgAl 10O 17:Mn solid solution

The optical properties of (1 − x)Ba 0.75Al 11O 17.25– xBaMgAl 10O 17 solid solutions doped with Mn 2+ have been evaluated using VUV excitation and emission spectroscopy. A band at 178 nm is improved with the increase of x and assigned to the absorption of the mirror layers of Ba 0.75Al 11O 17.25 and BaMgAl 10O 17. The excitation of spinel blocks in Ba 0.75Al 11O 17.25 and BaMgAl 10O 17 is found at a wavelength shorter than 160 nm and further assignments have been made: the AlO 4 5− cluster's absorption band could appear near 133 nm, the MgO 4 6− cluster's at 160 nm and AlO 6 9− cluster's at between the former two bands. The optimum emission intensity is about x = 0.2. It is concluded that the photoluminescence properties of Ba 0.75Al 11O 17.25:Mn 2+ or BaMgAl 10O 17:Mn 2+ can be improved by Ba 0.75Al 11O 17.25–BaMgAl 10O 17 solid solution with appropriate composition.

SIMS analysis of a multiple quantum well structure in a vertical cavity surface emitting laser using the mixing-roughness-information depth model

We have analyzed a multiple quantum well (MQW) structure in a vertical cavity surface emitting laser (VCSEL) epitaxial wafer using secondary ion mass spectrometry (SIMS). The two energy sputtering method is a very powerful method for providing a depth profile of a GaAs/Al 0.2Ga 0.8As MQW with a sufficient depth resolution and a large number of data points in a practical measurement time. This method consists of rapid high-energy sputtering for a top mirror layer and subsequent low-energy sputtering for an active layer. The resulting profiles were quantitatively evaluated using the mixing-roughness-information depth (MRI) model. The values of C concentration in modulation-doped Al 0.2Ga 0.8As barrier layers have been extracted from the original in-depth concentration profile reconstructed by the MRI model. The relationship between depth resolution of the resulting profile and surface morphology measured by atomic force microscopy (AFM) is also discussed.

Component operating with bulk acoustic waves, and having coupled resonators

The invention relates to a component operating with bulk acoustic waves, which comprises a mount substrate, thin-film resonators and an acoustic mirror, with coupled resonators being arranged jointly on this mirror. At least one mirror layer—a coupling layer—is in the form of an electrically conductive layer. This mirror layer forms coupling capacitances with lower electrodes of the resonators, thus resulting in deliberate capacitive coupling between the resonators which, according to the invention, is used in order to achieve additional pole points in the blocking areas of the filter transfer function. The capacitive coupling of the resonators may, for example, be influenced by partial structuring of the coupling layer in order, in particular, to shift the frequency of the pole points.

Cryogenic target with very thin “gold finger” heat pipe

An extremely light stainless steel heat pipe of 0.1 mm wall thickness and 5 mm diameter has been developed to transport heat from the liquid hydrogen/deuterium target to the cooling machine. As a further improvement an important reduction of the heat load to the cold parts of the system is achieved by coating the heat pipe and the target finger with a thin polished gold layer. This brings the radiation heat load from 1400 mW on the non-isolated stainless steel surface system down to 70 mW on the gold-coated system. A further reduction to 0.05 mW is achieved by using an aluminum heat shield at 50 K around the cold parts at 15 K. Finally, the heat load was further reduced by a factor 11, without changing the geometry, by coating both sides of the aluminum shield with a thin gold mirror layer. This new, very slim “gold finger” target system shows safe and stable performance even with a low power-cooling machine.

Reduction of oxide layer on Ru surface by atomic-hydrogen treatment

The reduction of Ru oxide was examined as a way of cleaning the cap layer of multilayer mirrors in extreme ultraviolet lithography (EUVL). Ru deposited on a Si surface was oxidized using electron cyclotron resonance (ECR) O2 plasma, and then treated with atomic hydrogen generated with a hot tungsten wire. An analysis of the surface composition by x-ray photoelectron spectroscopy and Auger electron spectroscopy revealed that atomic hydrogen removed the Ru oxide resulting from the ECR O2 plasma treatment. Additionally, atomic force microscopy observations showed that this treatment caused no increase in the surface roughness of the Ru. This indicates that the surface oxidation of EUVL mirrors is reversible, and can largely be eliminated by using atomic hydrogen and the proper cap layer.

Resonant nano-cluster devices

The resonance-enhanced absorption (REA) by metal clusters on a surface is an effective technique on which to base bio-optical devices. A four-layer device consisting of a metal mirror, a polymer or glass-type distance layer, a biomolecule interaction layer and a sub-monolayer of biorecognitively bound metal nano-clusters is reported. Experiments indicate a strong influence of the resonator homogeneity on the absorption maximum. Layer stability plays an important role in the overall performance of the device. Techniques and optimised lab protocols to set up biochips that use the REA process in the detection are presented. The sensors show one to three narrow reflection minima in the visible and or infra-red (IR) part of the spectrum and therefore they do not suffer from the spectral limitations associated with spherical gold colloids. Metal clusters (synthesised by thermal step reduction) as well as metal- dielectric shell clusters (synthesised by various shell deposition processes) are used to precisely shift the readout of the device to any frequency in the visible and near IR range. Disposable single-step protein chips, DNA assays as well as complex biochip arrays are established that use various DNARNA, antigen-antibody and protein-protein interaction systems.

Nanocluster Optical Resonance Devices for Molecular Structure Transduction

Resonant enhancement of metal cluster light absorption (REA) is an effective means to set up novel nanooptical devices. The boosting of optical absorbance is achieved by a resonant four component system. A metal mirror, a polymer or glass type nano-distance layer, a reactive bio-molecule layer and a sub-monolayer of bound metal nanoclusters are employed. Decisive for these types of devices and sensors is the precise nanometric assembly that couples the local field surrounding a cluster with its mirror-dipole. Metal clusters (synthesized by chemical reduction or deposited by vacuum coating techniques), metal-dielectric shell clusters (synthesized by multiple shell deposition processes) as well as high quality tuning of the distance layer enabled us to precisely shift the readout of the device to any frequency in the visible and near IR range. Sensors show one to three narrow or broad-band reflection minima in the visible and/or infra part of the spectrum. These are tuned by adjustment of the geometric parameters of the setup (Fig. (1)). Devices are used for detection of biorecognitive binding and monitoring structural changes of nucleic acids, proteins or analyte-recognitive polymers. The chip responds to the presence or absence of an analyte by a conformational change of the bio/polymer-transducer, thereby changing the cluster-mirror distance (or cluster distribution) and thus the optical absorbance and color of the chip. Disposable single step protein chips, DNA assays, RNA-conformation chips and polymer-artificial noses as well as complex arrays make use of the novel conformation-color transducer. Keywords: metal nano-clusters, resonance enhanced absorption, array, molecular conformation transducer, biochips