bluuebunny/crossref_metadata_2025 huggingface dataset:
A Comparison of Coherent Crosstalk Induced BER Floors in Four Types of N × N Space Photonic Switches
Authors: Blumenthal D. J. , Granestrand P. , Thylen L.
Published: February 2023

The all-optical multiwavelength network is a prime candidate for the future ” information highways”. In order to make these networks a practical reality, a number of questions need to be answered in terms of specifying components and subsystems. A critical issue involves bit error rate (BER) floors that degrade the normal statistical BER performance curves.
Mechanical Optical Fibre Cross Connect
Authors: Sjölinder Sven
Published: February 2023

Cross connect in the physical layer of the optical network is needed of several reasons. They may vary from operator to operator depending on the network architecture. The main reasons in many cases are installation of new terminals and service work on the fiber line. The cross connection is made at the ODF (=optical distribution frame) points in the network. The ODF:s are frequent and placed at the nodes in the network. To upgrade the network and install a new terminal, the appropriate connections are made manually at the ODF. To reduce labour cost and time Ericsson suggest to introduce a remotely controllable ODF. The remote control is made from anywhere in the network from a portable PC. With an remotely controllable ODF the documentation of the fiber network configuration may be made automatically and always be kept updated.
Thermal Considerations in the Design of Opto-Electronic Device Mounts
Authors: Buchholz D.B. , Lentine A.L. , Novotny R.A.
Published: February 2023

For some optoelectronic devices, the optical characteristics of the device are a strong function of the device temperature. An example of this is the self- electro-optic effect device (SEED).[1] SEEDs make use of the shift in wavelength of the exciton absorption maxima that occurs as a function of a changing electrical field across multiple quantum well material.[2] For a typical device, the absorption maxima must be shifted by 3 to 5nm to obtain good contrast between the absorptive and reflective states. A change in the device temperature, however, can also change the location of the exciton absorption maxima.[3] For GaAs/AlGaAs devices the absorption maxima shifts approximately 0.28nm/°C.[4] Thus, it becomes necessary to carefully design the SEED mount to minimize the temperature gradient and, therefore, this temperature induced shift across the chip.
Photonic ATM switching for broadband network services
Authors: Matsunaga Tohru , Sasayama Koji , Yamada Yoshiaki , Habara Keishi , Yukimatsu Ken-ichi
Published: February 2023

Asynchronous transfer mode (ATM) is a promising switching and transport technology for carrying multimedia traffic in broadband ISDN (B-ISDN). With ATM, end-to-end information is transported as fixed-size packets, called cells; this provides the flexibility needed for multimedia traffic, which ranges from kilobits per second to gigabits per second. ATM is now being introduced in LANs, MANs and WANs to carry data traffic and will soon penetrate widely into public networks carrying voice and pictures as well as data. The throughput of ATM networks will grow rapidly as the provision of fiber-optic subscriber loops stimulates the demands for broadband multimedia services. To meet this increasing demands, higher speed ATM switches will be needed.
Experiment on photonic ATM switches with WDM output buffers
Authors: Misawa Akira , Tsukada Masato
Published: February 2023

The asynchronous transfer mode (ATM) is attractive because it supports services having various bit rates. High-bandwidth optical technology using ATM will be the key to overcoming the throughput limitations of electrical systems. Some experiments on ATM switching with optical buffers have recently been presented[1, 2]. To increase the capacity of switching systems, wavelength division multiplexing is a promising technology in photonic switching[3]. We describe photonic ATM switches with wavelength-division multiplexed (WDM) output buffers. We use WDM technology to allow cell collision in a broadcast-and-select network, which leads simple network architecture. We also propose and experimentally demonstrate a WDM output buffer to read collided cells one by one.
Semiconductor Guided-Wave Switching
Authors: Zucker J.E.
Published: February 2023

Recently a systems pull from new fiber-optic networks has spurred development of custom semiconductor switches using novel materials, fabrication methods, and sophisticated optical design tools.
Bit Error Rate Studies of Diode-Clamped FET-SEED Optical Receivers
Authors: Woodward T. K. , Lentine A. L. , Chirovsky L. M. F.
Published: February 2023

The use of optics has been proposed as a technique to improve the performance of a variety of switching systems. In one scenario, large numbers of optical receivers and transmitters would be directly integrated onto semiconductor processing elements, as a means to reduce the communication problems of such elements. [1] In such a scheme, the receiver unit is particularly worthy of careful study, since it carries with it certain constraints on area and power consumption that are not generally present in other types of optical receivers. Accordingly, we have studied of the bit-error rate (BER) performance of one type of receiver being used in such systems, the diode-clamped optical receiver. This receiver is a high-impedance FET-based digital receiver whose basic operation has been described previously. [2, 3]
Optical Interconnection Technology for Large Computing and Switching Systems
Authors: Dutta Niloy K.
Published: February 2023

This talk will focus on current applications and future directions of optical interconnection technology. This technology will be initially driven by applications in large computing and switching systems. Advances in system architectures, subsystem modules and optoelectronic integrated circuits aimed at lower cost implementation of the entire system are necessary to create a wide application base for optical interconnection technology.
Technologies for Ultra-High-Bit-Rate Time-Division-Multiplexed Networks
Authors: Rauschenbach Kristin , Hall Katie , Moores John , Finn Steve , Barry Rick , Wong William , Haus Hermann , Ippen Eric , Haner Mark
Published: February 2023

Ultra-high-speed optical time-division multiplexed systems, operating at single stream rate of 100 Gbps, may offer important operating advantages over other multiplexing schemes. These advantages include increased "intelligence" within the network to perform dynamic routing which enables packet service and truly flexible bandwidth on demand. Transmission limitations and the availability of key technologies impact the system architectures and operating performance which can be expected from these systems. In this talk, we present recent developments in the architecture and technology for ultra-high-bit-rate networks.
Thermo-optical Digital Switch Arrays in Silica-on-Silicon for SDM Ring Networks
Authors: Hoffmann M. , Kopka P. , Voges E.
Published: February 2023

Thermo-optical digital switch arrays with a stabile zero voltage state were fabricated. The switches are based on the mode sorting principle in asymmetric waveguide branches.
Ultralow-Threshold Optical Switching in Nonlinear Active Periodic Multi-Port Devices
Authors: Radic Stojan , Maywar Drew , Agrawal Govind P.
Published: February 2023

We investigate novel switching/routing applications of nonlinear, active, periodic multi-port devices. Phase-shifts and nonlinearities allow ultralow switching thresholds of such devices.
A High-resolution and Wide-dynamic-range Method to Measure Dynamic Extinction Ratio of Electroabsorption Optical Gates by using an Optical Short Pulse as a Probe
Authors: Shibata Yasuo , Wakita Koichi , Yoshino Kaoru
Published: February 2023

The photonic asynchronous transfer mode (ATM) switch is promising because it may overcome the throughput limitations of electrical systems, and various ATM architectures have been proposed [1 ]-[3J. The optical gates are key components in these photonic ATM systems. These gates should be able to switch between cells within a guard time of a few nanoseconds, and their extinction ratio should be sufficiently large, typically more than 30 dB. The dynamic switching characteristics of an optical gate is usually estimated by directly observing the waveform using an oscilloscope, and the switching speed is determined from the 10%-to-90% rise/fall time. However, it is difficult to estimate the switching speed with a 30-dB extinction ratio by using the conventional method. Here, we propose a new and very simple measurement method for optical gates; this method has a high time resolution of 30 ps and a wide dynamic range of over 30 dB. We measured the dynamic extinction ratio of an electroabsorption (EA) optical gate module using this method, and found that the switching speed of an EA gate remains high even in a saturated condition.
Optical Transparency in Future Core Networks
Authors: Strebel B. , Caspar C. , Foisel H.-M. , Freund R.
Published: February 2023

Future optical core networks will transmit a high information capacity via a multichannel wavelength multiplex technique with channel bit rates of up to 10 Gb/s. The channels are switched in crossconnects with respect to space and frequency domain in the sense of a line switching. Wide areas of these networks could be designed optically transparent. In this case the channels have to be switched optically transparent via the crossconnects.
Novel Optical Cross-Connect Architecture for Restoration in Backbone Networks
Authors: Sano Hirohisa , Kitajima Shigeki , Kanetake Tatsuo , Sawada Yasushi , Fukashiro Yasuyuki , Tsushima Hideaki , Hanatani Shoichi
Published: February 2023

Recent progress of optical transmission technologies is going to realize practical systems up to 10 Gb/s. 40 Gb/s and further high speed transmission systems are now under development by introducing WDM (Wavelength Division Multiplexing) technologies to meet growing traffic demands. In such large capacity network, reliability and robustness are important issues because the increased capacity makes heavier damages to the network in case of line failure. Self-healing functions automatically restoring working lines to spare lines would be essential in the network.
100Gbit/S TDM Access Node Technologies
Authors: Islam Mohammed N.
Published: February 2023

Preliminary results for a 100Gbit/s TDM access node are obtained by integrating synchronized short-pulse fiber lasers, delay-line encoders, all-optical header processing and demultiplexing and electro-optic packet routing.
Active Blocking of Pilot Tones in All-Active Interferometric Mach-Zehnder Wavelength Converter
Authors: Kloch A. , Mikkelsen B. , Danielsen S. L. , Joergensen C. , Stubkjaer K. E. , Schilling M. , Wünstel K. , Idler W.
Published: February 2023

Management of future WDM networks will be fundamentally different from management of today's optical networks, because several signals at different wavelengths use the same fibre. It is essential for example that the signal wavelength can be identified with a simple and cost effective method. Therefore, pilot tones generated by amplitude modulation have been proposed for management and supervision of future WDM networks [1]. This raises the issue of interaction between the pilot tone and the network components.
Linear crosstalk properties of large WDM cross-connects
Authors: Larsen Claus Popp , Gillner Lars , Gustavsson Mats
Published: February 2023

Linear crosstalk generated in optical cross-connects should in certain cases be traced down to second order. This crosstalk is quantified, and approaches to reducing it are presented.
The Application of Ultrafast Optical Signals to High-Capacity ATM Switching
Authors: Joneckis Lance G.
Published: February 2023

The ability to design and build switching systems capable of handling the anticipated capacities of future communication networks present novel challenges. While the role for optics in the long-haul transport parts of the networks is clear, its role inside the switch has not yet been been established. Research spans the entire spectrum — from interconnects to optical logic. This research addresses the role of high-speed serial channels for short-distance optical interconnects in high-capacity packet switching fabrics. Traditional approaches have limited the role of optics to ferrying bits from point to point. As argued here, the marrying of ultrafast optical signals with conventional electronics significantly extends the role of optics from one of point-to-point interconnects to a more active one in the integral functioning of the switch without resorting to optical nonlinearities for processing and in a manner consistent with emerging network technology.
Holonic optical network for personalized multimedia communications
Authors: Murakami Koso
Published: February 2023

In order to satisfy the requirements for future communication network, ultra large capacity of information transport network and highly intelligent network capability are required. This paper proposes a novel network architecture, named Holonic Network, featured by distributed cooperative networking principle with autonomous routing.
Suppression of Dephasing by Deuteration of Amorphous Host Materials: The Case of Porphyrin-doped Polymers
Authors: Sakoda Kazuaki , Maeda Masayuki
Published: February 2023

As is widely recognized, the dephasing of an optical impurity doped in an amorphous host is mainly brought about by the interaction with two level systems (TLS)1). Because the microscopic structure of TLS is not clear and statistically distributed in usual cases, it is quite difficult at present to specify the relevant factors which govern the the relaxation of TLS's in a given material. However, we know that the relaxation is substantially the tunneling of atoms in the material.
Temporal Accessing of Frequency-Domain Optical Storage: Specific Approaches and General Considerations
Authors: Mossberg Thomas W.
Published: February 2023

The ultimate memory device would be one in which a bit of data is stored in every atom or molecule within a storage material. Such a memory would have an incredible storage capacity of somewhere in the range of 1022 bits/cm3. Traditional optical memories, whether two- or three-dimensional, can never hope to achieve atomic-level storage densities for the simple reason that minimally sized storage cells always have edge dimensions on the order of or larger than the wavelength of light employed. In the case of visible light, cubic wavelength scale storage volumes contain billions of atoms.
Time-domain optical data storage using Eu3+ ions in crystals
Authors: Mitsunaga Masaharu
Published: February 2023

The photon-echo memory[1], or the time-domain optical data storage, resembles the hole-burning memory [2] in that the inhomogeneous absorption line of a material is employed as a storage medium and the information is stored in it as a frequency-dependent absorption change with the resolution determined by the homogeneous width. Having the common memory capacity N given by the inhomogeneous-to-homogeneous width ratio, both types of memories share common problems like low-temperature operation, spectral diffusion and so on. Although a storage medium is common, storage techniques are definitely different for the two memories. The photon-echo memory utilizes the temporal interference effect between a reference pulse and a data pulse and their interference pattern is stored as a population grating in the frequency domain. In this sense this is a time-domain analog of holography where the spatial interference pattern between a reference beam and a data beam is stored in a medium as a population grating in the real space. Like the spatially diffracted beam from the read beam gives the information stored in the hologram, the “temporally diffracted pulse", or the photon echo, after the read pulse can give the information stored in the inhomogeneous distribution.
Photon-echo in Er-doped fibers: a new approach to femtosecond time-domain optical signal processing
Authors: da Silva V.L. , Silberberg Y. , Heritage J.P. , Chase E.W. , Saifi M.A. , Andrejco M.J.
Published: February 2023

Recently, interest in photon echo has been revived because of its potential application in time-domain optical memories1. Several demonstrations have been reported in gases and also bulk organic and inorganic materials at cryogenic temperatures2-4. In this paper, we report the observation of accumulated photon echo in Er doped optical fibers and demonstrate that these fibers can be used to store information on the subpicosecond time scale.
Spectral and Temporal Dynamics of Nonequilibrium Phonons in YAG:Pr3+
Authors: Wang Xiao-jun , Dennis W.M.
Published: February 2023

We have investigated the spectral and temporal dynamics associated with phonon decay in the YAG:Pr3+ system at a range of temperature between 9 and 25 K. Nonequilibrium phonons were generated using defect induced one phonon absorption (DIOPA) of far infrared (FIR) radiation1. Phonon detection was achieved optically using a variation of absorption vibronic sideband phonon spectroscopy2.
Light- and Thermoinduced Spectral Diffusion in Organic Amorphous Systems Measured via Hole Burning Stark Spectroscop.
Authors: Al’shits E.I. , Kharlamov B.M. , Ulitsky N.I.
Published: February 2023

Spectral diffusion (SD) is extensively investigated in the past years by means of hole burning method. In particular, evidences of thermo- [1] and lightinduced [2] SD are found. At the same time authors of [3] have found a strong dependence of the burned hole width on the burning fluence. As known, the classical model of a burning kinetics (hole broadening in this model is connected with saturation of the hole in the distribution function of impurity centers ) predicts enough weak hole broadening at the initial stage of burning [4]. It leads to a conclusion about possible additional mechanisms of hole broadening on an initial burning stage. One of such mechanisms can be SD, induced by the burning light (LISD). The influence of the burning power and fluence on the hole broadening was investigated by means of high sensitive Stark spectroscopy on chlorin in polyvinylbutyral (Chl/PVB). Thermoinduced SD (TISD) is investigated also, model of this process is proposed.
Electro - Optical, Multi-Stable Switches Based on Persistent Spectral Holes
Authors: Hanson David M.
Published: February 2023

Photochemical or photophysical transformations induced by highly monochromatic laser radiation can drastically reduce the concentration of molecules absorbing at a particular wavelength within an inhomogeneously broadened absorption band. These spectral holes can be broadened, removed, shifted or split by the application of an external electric field under appropriate conditions. This property provides a nonlinear response in sample transmission, absorption, or diffraction and can be coupled with feedback to produce novel electro-optical devices. These devices include electrically activated, frequency selective, monostable, bistable, or multistable switches.
Molecular Theory of Inhomogeneous Broadening in Glasses
Authors: Skinner J. L.
Published: February 2023

The absorption spectra of impurities in liquids, glasses, and crystals are often inhomogeneously broadened. This means that different impurities reside in different environments, which are static on the relevant time scale, and which perturb the energy levels of the impurities to produce a distribution of transition energies. This inhomogeneous broadening overwhelms the intrinsic linewidth of an individual impurity (the homogeneous linewidth), and is therefore a complicating feature of high-resolution spectroscopy. On the other hand, from a technological perspective inhomogeneous broadening is interesting because it is necessary for hole-burning, and hence for optical storage. And from a scientific perspective it is also interesting since it provides a probe of the local disorder in complicated condensed phase systems. In this talk I will discuss a molecular theory of inhomogeneous broadening in an attempt to understand this effect within a microscopic statistical mechanics framework.
Time-resolved transient hole-burning in disordered systems
Authors: Volker Silvia
Published: February 2023

Microsecond-living transient holes have been burned and probed, as a function of time and temperature, with a diode laser. Results are discussed in terms of spectral diffusion and compared with experiments on longer time scales in glassy and crytalline systems.
Hole-Burning Study of Optical Heating in Low-Temperatures Glasses
Authors: Gorokhovskii A.A. , Zavt G.S. , Palm V.V. , Stolovich A.L.
Published: February 2023

Zero-phonon lines (ZPL) in the spectra of impurities in solids are extremely narrow and intense. Due to these unique features, an impurity - guest can serve as a very sensitive probe of both the quasistatic structural disorder (inhomogeneous broadening) and dynamical processes (homogeneous broadening) in the matrix - host1). Site selective high resolution spectroscopy, in particular, persistent hole burning, can be successfully used to remove inhomogeneous broadening1,2) and can provide useful information about relaxation and propagation of elementary excitations in solids.
Time-Resolved Holeburning in YLiF4:Er3+ with Zeeman Scanning
Authors: Wang Y. P. , Meltzer R. S. , Wannemacher R. , Macfarlane R. M.
Published: February 2023

We report the results of time–resolved optical holeburning of Er3+ ions in YLiF4 (0.02%). In earlier work for H//c we described the time evolution of holes burned at 33kG using laser scanning over a frequency of 40MHz1 and we reported, using larger scans, the occurence of optical side holes. We now describe results for H⊥c with scans > 400 MHz using a new Zeeman technique for frequency scanning the optical transition frequencies which allow one to study the time evolution of the holes and their associated sideholes. The hole lineshapes evolve with time reaching a linewidth of ≃ 10 MHz after 600 μs. We identify the source of the time evolution of the hole shape as spectral diffusion resulting from mutual spin flips of the surrounding fluorine nuclei whose flip rates are strongly modified from the bulk rates by the presence of the large magnetic moment of the Er3+ ion which produces a "frozen core". A computer simulation which takes into account the details of the dynamics of the frozen core successfully describes the time evolution of the holes, confirming the dominant role of F nuclear spin flips.
Applications of Electric Field Effects on Persistent Spectral Holes
Authors: Maier Max
Published: February 2023

We studied the effects of an external electric field on persistent spectral holes in an inhomogeneously broadened optical transition of dye molecules embedded in crystalline or disordered solids.1 The results are applied to optical data storage in the electric field dimension, modulation and pulse forming of laser beams,1,2 and hybrid optical bistability.
Photochemical Hole Burning Stark Effect Studies on Octatetrane n-Alkane Mixed Crystals
Authors: Gradl Gerhard , Kohler Bryan E. , Westerfield Curtis
Published: February 2023

Given the enormous increase in resolution that can be realized in hole burning studies, the application of these techniques to determine the spectroscopic consequences of applied electric fields was a natural extension.[1] Much of the work in this area has focused on organic dye molecules in disordered glasses.[1-3] For most of these systems, the application of an electric field most often just broadens the persistent hole, although it has been shown that, in certain cases the orientation averaged effect of a randomly oriented solvent field plus a fixed applied field can lead to a partial splitting of the hole profile.[1,4]
Correlation between the Relative Zero-Phonon Electronic Transition Probabilities (Debye-Waller Factors) and the Matrix-Induced Spectral Shifts of Molecular Impurity Centers Doped Into Amorphous Hosts
Authors: Renge Indrek
Published: February 2023

The attainable contrast in spectrally highly selective photochromic materials critically depends on the Debye-Waller factors (DWF)/1/. The search for better hole-burning systems requires simple criteria for the selection of suitable dopants and hosts on the basis of molecular structure and, preferably, of room-temperature spectroscopy. The accumulated experimental data allow to establish reasonable relationships between the DWF and the differences of intermolecular interaction parameters in the ground and excited state (dipole moments, polarizabilities).
Free Volume Model of Thermally Induced Spectral Diffusion
Authors: Tsuchiya Jun , Takahashi Jun-ichi , Tanaka Hiroshi
Published: February 2023

An organic dye/polymer system, such as free base phthalocyanine (H2Pc) dispersed in polymethylmethacrylate (PMMA), has been interested in as a model material of new mass-storage for photochemical hole burning (PHB)[1]. There are, however, some unsolved problems in applying it to a plactical memory system. That is, the influence of polymers as a matrix over the static and dynamic properties of the system, such as, thermally induced spectral diffussion (TISD), homogeneous and inhomogeneous line width, burning efficiency and so on, has not been solved yet. TISD among them has a strong correlation to micro environment of a polymer dispersing a dye. The disorders in amorphous polymers are seen in wide energy range whose upper limit is determined by the glass transition of polymers. However, the lower limit is still left unknown , although some phenomena are known which are affected by low energy excitation. Recently, hole burning spectroscopy was successfully applied to investigate in the lower energy region [2]. Thermally induced conformation changes of polymers are said to have energy of same size to cause TISD in the lower energy region. Koehler et al. succeeded in explaining the the changes quantitatively from a combination of three independent processes, 1- phonon tunneling process, 2-phonon Raman scattering process and activation process [3]. The material parameters, however, that determine the changes are still unknown. We report TISD results of some dye/polymer systems and correlation between TISD and polymer properties.
Holeburning Optical Magnetic Resonance Imaging
Authors: Schiller Stephan , Byer R.L.
Published: February 2023

Scanning probe microscopy and gradient imaging are two techniques for imaging at sub-wavelength spatial resolution. Gradient imaging in the form of magnetic resonance imaging (MRI) has so far been demonstrated only in the radio- and microwave frequency domains [1]. An extension of MRI to optical frequencies for imaging (semi-) transparent objects is of interest because an optical photon detection process is inherently more sensitive than magnetic induction detection, potentially leading to increased spatial resolution. Rare-earth ions incorporated into a crystalline host are promising as a prototype system for demonstration of high spatial resolution OMRI.
XUV Mo/Si Multilayer Mirrors Deposited by RF Magnetron Sputtering
Authors: Montcalm Claude , Sullivan Brian T. , Pépin Henri , Dobrowolski J.A.
Published: February 2023

Mo/Si multilayer mirrors with a high reflectance at 132 Å were deposited using rf magnetron sputtering. The reflectance as a function of the deposition conditions was studied by varying both the argon partial pressure and the target power. To provide uniform coatings, the samples were rotated about their axis during deposition. In addition, the substrates could also be oscillated back and forth over the target giving rise to multiple passes during the deposition of each layer. With specially designed masks placed between the substrate and the target, this oscillation provides a further improvement in the uniformity. Furthermore, the multiple passes help average out any fluctuations in the deposition rate. Uniformity measurements of samples, made with and without the oscillations, will be presented.
A system for rapid characterization of multilayer mirrors and other soft x-ray optical components
Authors: Mrowka S. , MacGowan B. J. , Da Silva L. B. , Koch J. A.
Published: February 2023

We have developed a system capable of rapid characterization of optics in the soft x-ray region. X-rays from a laser produced plasma source are dispersed by a grating spectrograph onto a microchannel plate detector which is coupled to a CCD detector, figure 1. The CCD image is then read by a Macintosh computer. Part of the x-ray flux from the plasma is passed through the optic under test before being analyzed by the grating. In this way, spectral images with and without the test component in the optical path can be recorded simultaneously and compared to give throughput, figure 2. A .7 Joule Nd:Yag laser with 8ns pulse width, frequency doubled and capable of 10Hz operation, is focussed onto various targets to produce the x-ray pulses. A thin film filter is used to stop visible laser light from reaching the detector. Multiple diffraction orders from the grating are recorded so that the wavelength scale on the detector can be determined with high precision.
Limits to Ion Beam etching of Mo / Si multilayer coatings
Authors: Schlatmann R. , Lu C. , Verhoeven J. , Puik E.J. , van der Wiel M.J.
Published: February 2023

Recently ion beam etching of electron beam deposited metal layers on C has resulted in higher x-ray reflection coefficients1. In spite of the widely recognized importance of Mo/Si multilayer coatings for projection lithography, little work has been done to use the etching technique on multilayer mirrors made of this combination of materials. As Mo/Si multilayer mirrors of d-values greater than 12 nm. have already been made with reflectivities very close to the theoretical maximum2, our main interest is in multilayers with smaller d-values.
Low-radiation-damage multilayer coatings for the soft x-ray region
Authors: Hunter W.R. , Seely J.F.
Published: February 2023

Highly reflecting multilayer coatings (MLC), used to form resonant cavities for soft x-ray lasers(1) in which double- and triple-pass amplification occurs, can be destroyed by strong electric fields generated at the multilayer boundaries by intense soft x-ray radiation, rather than plasma debris from which the coatings are shielded. Any multilayer coating used in high field strength applications, FEL, x-ray projection lithography, etc., are subject to such damage. Electric field strengths can be reduced at the boundaries in MLCs by altering slightly the layer thicknesses of the final, or topmost, layers. Calculations are presented showing reduced field strengths caused by altering final layer thicknesses. The optical constants used in the calculations were obtained from Henke et al(2) and Palik(3) so similar computations may vary depending on the actual n,k values used but the basic concepts discussed herein are independent of the optical constants.
A multilayer quarter-wave plate of transmission type at a wavelength of 12.4nm
Authors: Kimura Hiroaki , Yamamoto Masaki , Nomura Hiroshi , Mayama Ko , Yanagihara Mihiro
Published: February 2023

In order to measure or to transform the polarization state in the soft x-ray region, we need a suitable quarter-wave plate. Kortright and Underwood[1] have shown theoretically that the transmission type multilayer has a good potential for a quarter-wave plate in the soft x-ray region. They demonstrated as a good example, the Mo/Si multilayer which has a periodicity of 9.0 nm and 20 periods at the wavelength of 13.8 nm, has the retardation Δp-Δs=86°, the polarizance (Ts-Tp)/(Ts+Tp) =42% and the throughput for s-component of 39% at the incident angle of 39.7° measured from the sample normal. The best quarter-wave plate should have the retardation equal to ±90°, the polarizance close to zero, and the high throughput over 50%. The multilayer designs presented here achieve these conditions necessary for good and useful quarter-wave plates.
High Resolution Electron Microscope Imaging and Quantification of Interface Structure in X-Ray Multilayers
Authors: Hull R. , Windt D.L. , Kola R. , Waskiewicz W.K.
Published: February 2023

We discuss the applications and limits of high resolution electron microscopy (HREM) to quantifying atomic-scale structure in X-Ray mirror multilayer (XMM) structures. It is shown how detailed processing of HREM images can yield quantitative measurements of interface planarity and diffuseness, which are critical parameters in determining the reflectivity of XMM structures.
Surface Roughness and X-Ray Scattering
Authors: Church E.L. , Takacs P.Z.
Published: February 2023

Interface roughness and diffusion limit the performance of x-ray multilayer (ML) stacks by generating unwanted scattering and reducing their efficiencies.
Substrate effects on x-ray specular reflectance and non-specular scattering from x-ray multilayers
Authors: Kortright J.B. , Nguyen T.D. , Tidswell I.M. , Lucas C.A.
Published: February 2023

It is common knowledge that substrate roughness plays an important role in limiting the specular reflectance of x-ray multilayers. However, there have been relatively few systematic experimental studies of the effects of substrate roughness on x-ray multilayer reflectivity. We have begun to investigate these effects by measuring the specular and off-specular scattering from a set of substrates with different roughness and from tungsten/carbon multilayers deposited simultaneously onto an identical set of substrates.
Elastic Properties of Strained Metallic Superlattices
Authors: Ariosa D.
Published: February 2023

Due to the improvement of metal deposition techniques in the last ten years, high quality epitaxial metallic superlattices made from non soluble materials with different crystal structures and important lattice mismatches are now available for varied applications. One exciting aspect of this kind of superlattices, among others, is their novel elastic properties (different from those of the constituents or their eventual alloys) due to the lattice deformation caused by epitaxial stress. As an example, one can cite the average lattice expansion in the growth direction and the softening of the sound velocity that have been reported for Mo/Ni superlattices[1, 2]. The above papers have been chosen because, as we will see later, they illustrate some controversial interpretation of X-Ray diffraction data and sound velocity measurements.
In Situ Growth Studies of Nanometer Thin-film Multilayers using Grazing X-ray Reflectivity and Ellipsometry
Authors: Lüken Eike , Ziegler Eric , Høghøj Peter , Freund Andreas , Gerdau Erich , Fontaine Alain
Published: February 2023

Multilayer-based X-ray optical components call for structures made of smooth and uniform layers with an abrupt interface as well as a high thickness repeatability over many layers. A wide bandpass high energy x-ray reflector illustrates this extreme case where one needs an in-depth graded period multilayer with several hundreds of layers [1]. Thus, in situ characterization techniques are essential to detect thickness fluctuations and are moreover very helpful to optimize the layers. This is the purpose of the two different methods described: grazing X-ray reflectance and optical ellipsometry.
Effect of substrate bias on roughness of Mo/SiO2 multilayers
Authors: Walton C. , Kortright J. B.
Published: February 2023

Multilayers of Mo and SiO2 were grown by magnetron sputtering with layer d-spacings of 20-40Å and fraction Mo about γ= 0.4. Dc biases of -120V were applied during the entire deposition time for some samples. Layer roughness was studied by specular and non-specular x-ray diffraction. In the non-specular scans the bias was observed to increase the peak-background ratio from about 102 to about 103. This is interpreted to show a decrease in interface roughness due to the bias.
Dual Ion Beam Assisted Deposition for Multilayer Production
Authors: Pedulla Joseph , Bartos Axel , Deslattes Richard D.
Published: February 2023

Low pressure ion sputtering of certain materials utilizing Dual Ion Beam Assisted Deposition (DIBAD) techniques is known to produce high quality optical films.1 This process makes use of ion beam sputtering at pressures much lower than those encountered, for example, in magnetron sputtering and simultaneously polishes the deposition with a second, low energy ion beam.2,3,4,5 We have been using this method to produce diamond-like carbon films exhibiting high density, extreme hardness, high thermal conductivity, and uniform thickness over an area of 4.6 x 103 mm2.6 These characteristics stimulated us to investigate their use as the low electron density component of multilayer x-ray optical elements.
Si/B4C Soft X-Ray Multilayer Mirrors
Authors: Falco Charles M. , Medower Brian S. , Slaughter J. M.
Published: February 2023

In previous work we have identified the Si/B material pair as useful for narrow bandpass optics at wavelengths above the Si L-edge, λ>124 Å.1,2 Unfortunately, useful boron sputtering targets are not generally available. However, excellent B4C targets are readily available, and the theoretical reflectivities of Si/B4C multilayers are only slightly less than for Si/B. In this wavelength region Si is the spacer and B4C is the absorber-thus breaking the standard rule of thumb, that good spacer/absorber pairs are low/high atomic number. Although the optical constants of B4C do not have strong contrast with Si, like those of Mo for example, the low absorption allows more interfaces to contribute to the reflection. Theoretical normal-incidence reflectivities calculated for ideal structures start at approximately 65% near the Si L-edge and drop with increasing λ to ~31% at 250 Å, compared to 77% and 37% for Si/Mo. Although the reflectivity is lower for Si/B4C, having more interfaces contribute results in narrow bandpass mirrors that are more desirable for several applications.
Determination of surface roughness of silicon wafers using soft-x-ray scattering*
Authors: MacKay J. F. , Teichert C. , Savage D. E. , Lagally M. G. , Wagner P.
Published: February 2023

Characterization of the morphology of polished surfaces, particularly on the nanoscale, has become increasingly important for a wide range of technologies. One method that is sensitive to roughness on this scale is hard x-ray scattering. However, the technique has limitations because measurements must be performed at grazing incidence to obtain sufficient signal. These limitations can be partly overcome by using soft x rays. In this study, we use soft-x-ray scattering to examine the morphology of Si wafers before and after the final chemical polishing step used in wafer fabrication. We use transverse (rocking) scans to map the diffuse intensity distribution normal to the surface. Both sample preparations yield a two-component profile, an instrument limited peak in the specular direction and broad diffuse component, suggesting a roughness with a long-wavelength cutoff. The samples that did not receive the final polishing step showed much greater diffuse intensity, indicating that they are much rougher. The soft-x-ray measurements are in qualitative agreement with optical scatter measurements. Results will be compared with atomic force microscopy measurements and discussed in terms of the band pass of the respective measurements. Efforts will be made to compare the rms roughness and the power spectral density extracted from these techniques.
Imaging Cross Section Of X-ray Multilayer By STM
Authors: Wang Qi , Knight L. , Thorne J.
Published: February 2023

Cross section information is important in the study of x-ray multilayers. The traditional technique in this area is TEM. One of the limitations for TEM method is that the image is not from the surface of the sample but over an average of 10-20 nm in depth. STM, on the other hand, is a surface-sensitive technique. Comparing with TEM, STM has another advantage that STM is capable of obtaining information about the electronic structure of the materials. Like TEM, STM can also provide images with atomic lateral resolution. Potentially, STM is a very powerful tool in the study of x-ray multilayer.
Characterisation of Mo/Si multilayers with small angle reflectivity measurements.
Authors: Voorma H.-J. , Louis E. , Koster N. B. , Bijkerk F. , Wiel M. J. v.d.
Published: February 2023

We developed an optical system for soft x-ray projection lithography [1] with a laser plasma x-ray source. In the optical system Mo/Si multilayer mirrors are used for near normal incidence reflectivity. High reflectivity of each multilayer is mandatory because in the optical system four reflecting surfaces are used. A reliable tool for characterisation of multilayers is needed in the process of determining the optimum parameters for the production of high reflectivity multilayer mirrors. Therefore we developed software to analyse the hard x-ray reflectivity measurements. With this software, that is based on a fast Fourier transform (FFT) of the Bragg peaks, a distinction between interface-roughness and layer-thickness errors can be made. These two parameters have considerable influence on the near normal incidence reflectivity. Furthermore, reflectivity measurements are done at various wavelengths to find the material densities. These are also important parameters for the near normal incidence reflectivity. This article will restrict itself to the analysis Mo/Si multilayers deposited at 36°C and 215°C with or without ion etching. These multilayers are made for a wavelength of 13.5 nm at normal incidence.
Broad-band focusing of hard x-rays using a supermirror
Authors: Høghøj Peter , Ziegler Eric , Susini Jean , Freund Andreas K. , Dan Joensen Karsten , Gorenstein Paul
Published: February 2023

Until recently, the use of reflective optics at short wavelengths was limited by the low critical angles of minor materials. Single coating mirrors are impractical for energies above ~ 40 keV, because the approximate relation E[keV]· ·θ [mrad] ≤ √ 80 · Z, (where θ is the incidence angle and Z is the atomic number of the mirror material) must be fulfilled. For neutrons the use of graded d-spacing multilayers, so-called supermirrors, has helped to considerably increase the usable angles and has facilitated the construction of flux concentrators at energies where single coatings do not perform well1,2,3. We have previously reported on supermirrors for high energy x-rays4,5. For energies above 40 keV and away from absorption edges, supermirrors show significant reflectivity out to E[keV]· θ[mrad] ≤ 6.2·103/dmin[Å], where dmin is the minimum period of the supermirror. In this summary we describe the first focusing of a high energy polychromatic x-ray beam with a W/Si supermirror.
Wedge and Strip Image Readout Systems for Photon Counting Detectors in Space Astronomy
Authors: Siegmund O.H.W. , Lampton M. , Bixler J. , Chakrabarti S. , Vallerga J. , Bowyer S. , Malina R.F.
Published: February 2023

We discuss the application of wedge and strip anodes to microchannel plate detector systems for extreme and far ultraviolet, and visible wavelengths. Performance data, obtained as a result of calibration of the Extreme Ultraviolet Explorer Satellite (EUVE) [1] detectors (open face) and the Faust-Spacelab far UV sensors [2] (sealed tube, proximity CsI cathode, Figure 1), is presented. The flexibility of anode design structures for differing applications and performance in terms of spatial resolution, image linearity and stability, counting rate capability, and small scale differential linearity and stability are considered.
Photon Counting Imaging on the Space Telescope
Authors: Boksenberg A.
Published: February 2023

Summary not available
Photon Counting Array Detectors for the Fuse/Lyman Satellite Telescope
Authors: Roberts E , Stapinski T , Rodgers A
Published: February 2023

The development and performance of advanced, multi-channel photon-counting detectors for the FUSE/Lyman satellite ultraviolet telescope is described.
Signal-to-Noise in Photon Counting Speckle Interferometry with Real Detectors
Authors: Ebstein Steven
Published: February 2023

In speckle interferometry, one estimates the angular power spectrum of short-exposure images degraded by atmospheric turbulence. The power spectrum is a random process due to the variability of atmospheric conditions and due to the stochastic nature of photodetection.
Photon Statistics Limitations in Precision Astrometry
Authors: Meinel Aden B. , Meinel Marjorie P.
Published: February 2023

Image centroiding is the traditional way to measure star positions for astrometry. Interferometry is a way to obtain higher one-dimensional resolution with equal total photon collecting area than is obtained with a circular unobscured aperture. Interferometry is now being proposed as a better way to measure star positions. We have examined both methods and find that the comparison of the two methods is dependent upon the spatial and temporal photon statistics involved.
Multichannel Raman spectroscopy of monolayers on surfaces using a CCD Detector
Authors: Murray Cherry A.
Published: February 2023

Currently available detector technology is beginning to make possible high resolution spontaneous Raman spectroscopy of surfaces, metals, and other systems containing as few as 1011 molecules. Raman scattering is an inelastic process in which an incident photon either gives up or creates an intrinsic quantum of energy in matter. We are interested in the use of Raman scattering as a probe of fingerprint vibrational levels of molecules, for which the change of energy of the incident light is about 0.01 - 0.1 electron volts or 80 - 800 cm−1. The advantages of Raman scattering as a vibrational spectroscopy are its high resolution coupled with a large frequency range. Typically 1 cm−1 resolution is all that is needed for a tenth the linewidth of a vibrational mode of an adsorbate on a metal surface, for example; and a range of 20 to 4000 cm−1 spans a reasonable vibrational range for most adsorbates. Typical surface bonds for small molecules are in the 100 to 500 cm−1 range. Both the resolution and spectral range are quite easy to achieve with visible laser collection optics, detectors and spectrometers. Spontaneous Raman scattering is a process that can be described by second order perterbation theory involving two electric dipole matrix elements and a resonant denominator Raman scattering has different quantum mechanical selection rules for allowed vibrational modes than do infrared absorption (IR) or high resolution electron energy loss (HREELS), and complements these other more traditional surface vibrational spectroscopies. At the same time, Raman scattering has about an order of magnitude better freqency resolution than HREELS and considerably better frequency range than IR, which is currently limited to above about 1000 cm−1 in surface experiments.
Photon-limited Scene Matching Using Histogram Analysis
Authors: Zweig David A. , Morgan C. J.
Published: February 2023

Owing to advances in photon detection, there is a developing interest in identifying objects from a limited number of photons. Such applications include astronomy, night vision, long-range target recognition and medical and industrial radiology. In each of these applications it is desirable to extract the maximum amount of information from a limited number of photons. In this paper, we propose a method for object recognition based on the formation of irradiance level histograms for a group of known objects. The technique is used to construct a binary histogram which requires fewer photons than a correlation filter to identify a particular object.
Effect of Nonnegativity Constraints on Detectability
Authors: Hanson Kenneth M.
Published: February 2023

It is demonstrated that under certain circumstances the use of a nonnegativity constraint in tomographic reconstruction from noisy projections can improve the detectability of objects.