bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Propagation and Beam Coupling in Photorefractive Media
Authors: Hendow Sami T. , Jabr Salim N. , Shakir Sami A.
Published: February 2023

Numerical wave propagation in photorefractive media requires the implementation of a generally complex and continuously changing index of refraction in the solution. This makes the diffraction integral of Rayleigh and Sommerfeld1 inappropriate for treating cases of nonlinear propagation. Instead, the direct solution of the wave equation is used.2,3 In this paper we present a numerical solution for propagation in a one dimensional infinite slab. The numerical code is applied to the case of energy transfer between two beams in photorefractive media.
Crystal Growth, Electrooptic and Photorefractive Properties of Iron Doped Barium Titanate
Authors: Godefroy G. , Ormancey G. , Jullien P. , Lompre P. , Ousi W. , Semanou Y.
Published: February 2023

It is well known that BaTiO3 is a particularly promising material for applications in optical data processing and phase conjugation using four wave mixing. Recently Klein and Schwartz [1] found that iron impurities, in "pure" samples are the most likely source of photorefractive effects.
Reduced KNbO3-crystals for fast photorefractive nonlinear optics
Authors: Voit E. , Zha M.Z. , Amrhein P. , Günter P.
Published: February 2023

One of the most important parameters for applications of photorefractive crystals is the speed of the photoinduced grating build-up time. This time constant depends on the reduction state of the photoactive defects. One is primarily interested in a rapid redistribution of photoinduced charge carriers. This is the case in materials having a small concentration of trapping centers NA where the drift length Ld= φµτe is large (comparable to the grating fringe spacing; µ: carrier mobility, τ=(γrna)−1carrier life time, γR carrier recombination constant, E electric field). The relative concentration of donor (ND) and acceptor centers (NA) can be influenced by reduction treatment in oxygen octahedra ferroelectrics such as KNbO3.
Crystal Growth of Barium Titanate Photorefractive Crystals
Authors: Pollak T.M. , Schuneman P.G.
Published: February 2023

Barium titanate (BaTiO3) exhibits very strong non-linear optical properties and is utilized for numerous optical applications, including optical phase conjugation, laser optical storage and image processing. The photorefractive effect is reportedly the phenomenon resulting in the unique non-linear optical behavior. As charge migration is a key process in the photorefractive effect, the formation of crystalline defects giving rise to the charge carriers is of fundamental importance. The nature of the crystalline defects influencing photorefractivity in BaTiO3 is presently unknown, however, variations in crystal growth or other thermal processing does influence the formation of photorefractive charge carriers. Optimized crystal growth processes and thermal annealing can be employed to develop key material parameters and improve the overall photorefractive efficiency of BaTiO3.
Terahertz Optical Asymmetric Demultiplexer (TOAD)
Authors: Sokoloff J. P. , Prucnal P. R. , Glesk I. , Kane M.
Published: February 2023

We present a new device capable of demultiplexing Tbit/s pulse trains which uses less than one picojoule switching energy and can be integrated on a chip.
Translation of Laser Tuning Experiments into Networks
Authors: Giglmayr Josef
Published: February 2023

The relationship between the organization of laser tuning and the arising networks in the space-frequency domain is made transparent. The interconnection topologies of interest are reviewed and some crucial problems are discussed. Several examples (multiplexing on vectors) are evaluated by the number of channels crossed during the generation of frequency interconnects and during frequency switching.
Photonic ATM Cross-Connect Node Based on Cell Aggregation and Compression
Authors: Cinato P. , Bostica B. , Calzavara M. , Gambini P. , Puleo M. , Vezzoni E.
Published: February 2023

A photonic ATM cross-connect is presented, where cell aggregation and compression are adopted to achieve a high throughput and high performance node. Experimental results on specific subsystems are presented.
Role of Tunable-Transmitter Wavelength-Division-Multiplexing Star-Coupler Architecture in High-Performance Multigigabit Asynchronous-Transfer-Mode Switching
Authors: Santoro Mario A. , Eng Kai Y.
Published: February 2023

By incorporating a tunable-transmitter wavelength-division-multiplexing design in a 2.5 Gb/s/line Growable Switch Architecture we obtain the best possible switching performance with the smallest number of wavelengths and simple control, independent of switch size.
Acoustooptic Crossbar Photonic Switch
Authors: McLeod Robert , Weverka Robert , Wu Kuang , Wagner Kelvin , Mickelson Alan , Roth Richard
Published: February 2023

Emerging serial optical communication standards such as Fiber Channel require a large optical crossbar (called a “fabric”) that routes signals in a circuit-switching manner with a few μsec switching time. The switching fabric must be able to transmit multi-gigabit per second optical signals and should be transparent to wavelength division multiplexing (WDM) protocols, and thus cannot be implemented in existing Silicon or Gallium Arsenide technology. The alternative is to use an all-optical switch which can quickly establish physical connections between fibers.
A Fast LD Wavelength Switching with Rapid Stabilizing Control for WDM Network
Authors: Shiozawa Takahiro , Shimosaka Naoki , Fujiwara Masahiko , Shiragaki Tatsuya
Published: February 2023

Recently, requirements have been increasing for large throughput asynchronous transfer mode (ATM) cell based networks, such as ‘transfer networks’ [1] and local area networks (LANs) [2]. However, pursuing larger throughput only by improving transmission speed cannot satisfy future requirements. Wavelength-division multiplexing (WDM) optical networks are promising for increasing throughput. For effective utilization of this enlarged throughput, a ring topology with appropriate fairness control (e.g. [2]) is preferable to a star topology [3], considering the latter's inevitably complicated contention-free access control (for example, a token passing protocol) that imposes a delay on each cell. Recently, we have proposed a WDM ring optical network for ATM signals with high throughput and simple access protocol [3]. In this paper, a novel scheme is proposed and experimentally confirmed for fast laser diode (LD) wavelength switching with rapid stabilizing to its predetermined wavelength, which is the key technology for the proposed network.
Optoelectronic Logic Arrays Using the Light Amplifying Optical Switch (LAOS)
Authors: Geib K. M. , Feld S. A. , Beyette F. R. , An X , Alhokail H. , Hafich M. J. , Robinson G. Y. , Wilmsen C. W.
Published: February 2023

The massive parallelism and interconnectivity possible with optoelectronic systems requires the development of fast optoelectronic array processors. The arrays must be fast, with frame rates greater than 20 MHz, in order to effectively compete with electronics. The arrays must also have a large number of pixels (> 104) and perform a logic or memory function. We have designed, fabricated and are in the process of testing an array that can meet these system requirements. This paper discusses our array design and presents some preliminary data.
Complete All Optical Switching of Visible Picosecond Pulses in Birefringent Fiber
Authors: Rothenberg Joshua E.
Published: February 2023

Numerous approaches have been recently pursued in all optical switching in fiber devices.1-4 A number of these efforts have demonstrated the principle of switching based upon cross-phase modulation (XPM) by a control pulse, but have failed to achieve high switching contrast ratios.1-2 For anomalous dispersion, switching of soliton like pulses based upon XPM by a second wavelength has been accomplished.2 Uniform XPM and high contrast switching of visible signal pulses was achieved using a long duration control pulse of a different color so that the control walks through the signal owing to group velocity dispersion.4 In this paper the need for a second source is eliminated by using cross-phase modulation from a short, orthogonally polarized control pulse of the same frequency, in a birefringent fiber. It is found that 50:1 switching contrast is obtained and that the effects of broadening of the control pulse are significant and must be considered.
Demonstration of a Polarisation Rotation Gate in GaAs/AlGaAs Multiquantum Well Waveguides
Authors: Snow P. A. , Day I. E. , White I. H. , Tsang H. K. , Penty R. V. , Grant R. S. , Su Z. , Sibbett W. , Soole J. B. D. , LeBlanc H. P. , Gozdz A. S. , Andreadakis N. C. , Caneau C.
Published: February 2023

Recent work on the development of integrated optical devices for nonlinear switching and processing has focused on the performance of Mach Zehnder1 and directional coupler2 switches. However previous research into optical fibres has identified the potential of the birefringent polarisation gate3 which is known to have better stability against external fluctuation than interferometric gates based on independent optical paths.
Ultra-Fast Wavelength Switching and Wavelength Conversion with Strained-MQW-Y-Lasers
Authors: Idler W. , Baums D. , Lach E. , Laube G. , Schilling M. , Wünstel K.
Published: February 2023

To meet the demands of fast optical switching architectures we need photonic devices with short electronical as well as optical switching times. These requirements concern all degrees of freedom: frequency/wavelength, space and time. With Y-lasers we have already demonstrated fast electrical tuning in wavelength and space with 1 GHz /1/ and all optical wavelength conversion /2/.
Limits on Smart Pixel Granularity: Power Dissipation and Self-Inductance
Authors: Stirk Charles W.
Published: February 2023

Physical effects are present in high-performance systems that limit system packaging and architecture. For example, the finite capabilities of heat dissipation technology restrict the number of simultaneously switching elements, their density and switching speed for optoelectronic devices. In addition, the self-inductance of power and ground connectors between levels of packaging also limit the number of devices switching simultaneously. This paper examines the impact of these two effects for optoelectronic integrated circuits (OEIC). For high-speed optical I/O the power and ground pin-out can be comparable with the number of optical channels: hence, optical interconnects do not necessarily solve the package pin-out problem. Furthermore, these effects mandate large-grained smart pixels for high-bandwidth interchip communication.
Ultrafast Wavelength Tuning and Wavelength Conversion with Strained-MQW-Y-Lasers
Authors: Idler W. , Baums D. , Lach E. , Laube G. , Schilling M. , Wünstel K.
Published: February 2023

Electrical and optical wavelength tuning with 500 psec speed is demonstrated with an interferometric Y-laser. Fast optical wavelength conversion is achieved with 2.5 Gbit/s data across 45 nm.
Electrically Actuated Nanomechanical Integrated Optical Switches
Authors: Pliska P. , Lukosz W.
Published: February 2023

We demonstrated modulation, switching, and deflection of guided waves in (non-electrooptic) waveguides on silicon, the required effective-index changes being induced nanomechanically by electrostatic forces.
Limits on Smart Pixel Granularity: Power Dissipation and Self-Inductance
Authors: Stirk Charles W.
Published: February 2023

Power dissipation and self inductance in high performance systems constrain their packaging and architecture. For high-bandwidth communication, power dissipation favors large-grain pixels. Self-inductance also favors large-grain pixels for high-bandwidth inter-chip communication.
High-Speed 2-D CMOS Designs of Bypass-and-Exchange Switch Arrays for Free-Space Optoelectronic MINs
Authors: Kibar Osman , Marchand Philippe J. , Esener Sadik C.
Published: February 2023

In a free-space optoelectronic multistage interconnection network, electronic bypass-and- exchange switches are required to do the local routing. It has been shown that for a MIN with N inputs and outputs, the bandwidth and the power consumption are optimized if the electronic switch planes are partitioned into
N switches [1]. Thus, each switch has
N inputs and
N outputs and is defined as
N×N switch. Two separate circuits, that use an optimized 2-D layout and are compatible with the Optical Transpose Interconnection System (OTIS) have been designed and analyzed. The first design (design A) was used as a proof of concept for the optimized 2-D layout, the second design (design B) is a bi-directional self-routing concept that uses 3 level logic.
An Optical Cross-Connect Architecture Incorporating Failure Recovery Using Reserved Wavelengths
Authors: Kuroyanagi S. , Hironishi K. , Maeda T.
Published: February 2023

Optical path layer technologies are expected to be crucial in creating a flexible network architecture and expanding network capacity in broadband ISDN (B-ISDN) [1]. The optical cross-connect (OXC) is the main component in an optical transport network. OXC systems must offer a compact, economical switch architecture that allows effective modular growth. The OXC systems must also have robust network failure recovery, because large-capacity optical networks require a highly reliable optical path layer.
Wavelength stabilization as a practical standard light source for wavelength division multiplexing system on 1.55µm
Authors: Tachikawa Yoshihiko , Suzuki Yasuyuki , Arihara Mamoru , Inoue Takeshi , Nakajima Shinichi , Hirata Takaaki , Ishikawa Jun
Published: February 2023

Recent progress of communications requires the next generation of fiber optic communication systems such as wavelength multiplexing system (WDM) or optical time division multiplexing system (OTDM). For the demand on increase of transmission capacity, it is important to consider the wavelength dispersion of an optical fiber network and the gain spectrum of an erbium doped fiber amplifier. In order to realize above fiber optic systems, several wavelength standards are now under development.1),2),3) In this paper, we describe the construction and the specifications of a light source stabilized to an absorption line of hydrogen cyanide (HCN) gas on 1.55µm band.
A Novel Photonic Architecture for High Capacity ATM Switching Applications
Authors: Chiaroni D. , Chauzat C. , De Bouard D. , Gurib S. , Sotom M. , Gabriagues J.M.
Published: February 2023

More and more, the capacity of telecommunication networks will have to be increased so as to meet the future needs of the customers in terms of bandwidth. ATM has been identified as a standard switching technique for the future broadband network. For these reasons an optical ATM switching architecture [1] has been proposed and recently demonstrated with the build up of a 4×4 switching matrix operating at 2.5 Gbit/s.
Fanout, Replication, and Buffer Sizing for a Class of Self-Routing Packet-Switched Multistage Photonic Switch Fabrics
Authors: Krishnamoorthy Ashok V. , Kiamilev Fouad E.
Published: February 2023

We present the Stretch multistage switch; a class of self-routing multistage interconnection networks that provides a continuous performance-cost tradeoff between two of its degenerate forms: the Knockout switch1 and the Tandem banyan network2. Stretch networks utilize simple destination tag routing and can be designed to achieve low delay and arbitrarily low blocking probabilities for random, permutation, and non-uniform traffic without using internal buffers in the switches. These qualities make them useful for both fast packet (ATM) switching and multiprocessor architectures. The flexibility of the architecture helps the designer to accommodate user requirements in terms of packet loss probabilities while allowing the structure of network to be driven by technology considerations. The advantages of the Stretch multistage switching fabric come to bear in cases where the number of channels is very large and the ability to use fanout in the network is available. These considerations make it a good candidate for a photonic implementation. In this paper, we discuss the design of switch fabric and suggest a possible photonic switch implementation.
Multi-channel Optical Filters Using birefringent planar optical Platforms
Authors: Hirabayashi Katsuhiko , Yamaguchi Masayasu
Published: February 2023

For WDM systems, tunable optical filters have been actively studied. [1] Most tunable filters can select only one wavelength at a time, the tuning speeds are as slow as 1 - 100 ms, and they need wavelength-stabilizing circuits. For communication switching, filters are thus required that can select several wavelengths simultaneously, and can switch quickly without stabilization. To meet these requirements, we have studied a novel multi-channel filter consisting of a birefringent planar optical platform.
All-Optical Self-Routing Switch Using a Nonlinear InGaAs/InAlAs MQW Waveguide
Authors: Kanetake T. , Tanaka S. , Inoue H.
Published: February 2023

Intelligent society demands diverse communication services such as the telephone, facsimile and the high definition TV. To improve flexibility and efficiency of the transmission system under these diverse demands, Asynchronous Transfer Mode will be installed as a new standard method. In this mode, information is divided into many cells of a constant bit-length with headers. Each cell chooses its own route by itself, depending on address information in its header. To realize ATM network for massive demands in future, optical communication technology will be applied. For this, an all-optical self-routing switch, which changes signal route by address information on optical signal itself, is strongly required. Figure 1 shows our approach to realize this switch. That is a Mach-Zehnder interferometer with nonlinear optical medium inserted into one arm. An address light, whose wavelength is slightly different from that of a signal light, controls the phase status of the interferometer through the refractive nonlinearity. Therefore, it also controls which output-port a signal cell passes through.
InP-based MQW optical devices for photonic switching
Authors: Inoue Hiroaki , Ido Tatemi , Sano Hirohisa , Kanetake Tatsuo
Published: February 2023

Increasing demands for high-bit-rate transmission technologies enabling interactive multimedia era reach to establishing the global information infrastructure based upon optical tera-bit/s telecommunication network.1) The optical network, which fully utilizes optical bandwidth of fiber, will exploit the functionality offered not only by TDM(Time Division Multiplexing) but also by WDM(Wavelength Division Multiplexing) technologies. The optical high-bit-rate(TDM) and WDM transmission technologies accompanied by the optical node2) technologies such as WDM-ADM(Add/Drop Multiplexer) and WDM-OXC(Optical Crossconnect) require the even more functional optoelectronic devices. Semiconductor based optical devices is becoming more and more of a requirement as key devices, in terms of the advanced functionality, such as high- speed modulators over 10Gb/s, compact optical amplifiers, matrix space switches, wavelength converters, and so on.
Low-Loss Polarization-Insensitive High-Speed InP/InGaAsP Optical Space Switch Modules Fully Packaged with Electronic Drivers and Single-Mode Fibers
Authors: Krähenbühl R. , Vogt W. , Hunziker W. , Schneibel H. , Bauknecht R. , Gini E. , Melchior H.
Published: February 2023

High performance InP/InGaAsP space switch modules with a four switch matrix, four input, four output fibers and electronic drivers are presented. Fiber-to-fiber losses are 7 dB, polarization sensitivity is within ±0.5 dB, on-off switching times are faster 200 ps. Crosstalk is below -15 dB/ -30 dB in regular/dilated arrangements over 1.53-1.56 μm wavelength range.
Direct Optical Demux from 10 Gbit/s to 2.5 Gbit/s NRZ Signals Using a Side-Injection-Light-Controlled Bistable Laser Diode
Authors: Nonaka Koji , Kobayashi Fumihiko , Tadokoro Takashi , Kishi Kenji , Amano Chikara , Itoh Yoshio , Kurokawa Takashi
Published: February 2023

We have demonstrated direct optical demultiplexing of NRZ signals using a semi-insulating InP buried side-injection-light-controlled bistable laser diode. The 2.5 Gbit/s demultiplexed output signals are selected and bits-width is converted in the same chip from 10 Gbit/s NRZ optical input- signals.
Low Voltage, Wavelength and Polarisation Independent Micro-Opto-Mechanical Switch Integrated On Silicon
Authors: Ollier E. , Mottier P.
Published: February 2023

An improved micro-switch for optical networks is presented. Fully integrated on silicon substrate and especially characterized by wavelength and polarization independence, low insertion losses and low driving power, it is very well suited for optical networks applications.
Network Requirements on Optical Switching Devices
Authors: Gustavsson Mats , Gillner Lars , Larsen Claus Popp
Published: February 2023

Network requirements on optical switching devices are discussed; in particular, a statistical model of accumulation of interferometric crosstalk is presented, analysed, and illustrated.
All-optical EX-OR gate based on an integrated interferometric Mach- Zehnder wavelength converter
Authors: Zucchelli L. , Bendelli G. , Raspollini D. , Puleo M. , Gambini P. , Schilling M. , Idler W. , Wünstel K.
Published: February 2023

All-optical signal processing of digital signals will be used in future communication systems and possibly also for optical computing [1]. The all-optical implementation of the logic Exclusive-OR (EX-OR) operation is of great interest as it may be used, among other applications, for optical correlation between two independent signals or optical clock recovery.
Picosecond Pulse Train Switching by Four-Wave Mixing in Semiconductor-Laser Amplifiers
Authors: Schmidt C. , Diez S. , Ludwig R. , Weber H. G.
Published: February 2023

We study the dynamic switching properties of a semiconductor-laser amplifier using four-wave mixing with picosecond pulses. The dependence on the injection current is investigated.
The Concept and Technologies Behind a Metropolitan Optical Network
Authors: Evaldsson P. , Johansson S. , Almstr E. , Hubinette C.
Published: February 2023

Last year was a landmark for Wavelength Division Multiplex (WDM) systems, in that they became commercially available. Several of the long-distance network operators introduced WDM into their trunk networks. These systems are for the point to point transmission, and the question remains if WDM will also be cost effective in the metropolitan area where the prerequisites are different. Some of the characteristics are a dense fiber structure, granular traffic pattern, lower bitrates and short transmission distances (<50km). In the ACTS project METON (Metropolitan Optical Network) the main goal is to establish the use of WDM in a metropolitan area network. This paper describes the METON network concept and its development of advanced network elements.
Increased Capacity of a Bidirectional SDH Self-Healing Ring Using WDM
Authors: Cadeddu R. , Caponio N. , Cerisola M. , Ferraris G. , Finotti R. , Lano R. , Mariconda A.
Published: February 2023

The use of SDH in telecommunication networks has allowed the production of equipment with add-drop functionality. The most common application of such equipment is in ring networks, commonly named self-healing rings, that are now extensively used because of their key feature of failure survivability.
Error-free 600MB/s data transmission between switching LSIs for a parallel computer using 12-channel optical interconnection modules
Authors: Inoue Hiroaki , Nishimura Shinji , Hanatani Shoichi , Matsuoka Hiroshi , Yokota Takashi
Published: February 2023

Synchronously Parallel fiber optical interconnection technologies are attractive for high- throughput computer and switching systems, such as massively parallel computers and ATM switches. Because they would be able to eliminate a connection bottleneck caused by conventional copper cables using optical fibers featured in high-speed and long-distance transmission and wiring1). We have proposed optical interconnection with 12-channel fully- integrated CMOS-interface modules for low skew and error-free unformatted data(DC- 250Mbit/s) transmission2,3). This paper reports on our error-free(80 hours) 600MB/s(4.8Gbit/s) data transmission between switching LSIs designed for the massively parallel processing computer4).
All-Optical Switching at 100-Gb/s Rates via Coherent Control of Excitons in a Semiconductor Microcavity
Authors: Citrin D. S. , Norris T. B.
Published: February 2023

Although it is well known that the bandwidth afforded by optical fibers exceeds 1 Tb/s, the bandwidth of networks presently implemented is in the 1-10 Gb/s range. Considerable improvements are required in components used for modulation and demodulation of signals in optical communications networks. A central problem to be solved for the deployment of 100-Gb/s systems is the development of appropriate all-optical switches. A number of optical switches based on semiconductors, in which a control pulse gates a signal pulse, have been demonstrated. However, one of the main problems with switches based on semiconductors has been that while the switch may have a fast opening time, the closing time is very slow since the switch is open for as long as carriers (electrons and holes) are present in the material, limiting the bandwidth quite severely. In this talk we describe a technique which provides for fast closing as well as opening of the switch to give the required bandwidth.
Wavelength Interchangeable Cross-Connects with Reduced Complexity
Authors: Zhong Wen D. , Lacey Jonathan P. R. , Tucker Rodney S.
Published: February 2023

Optical cross-connects (OXC’s) will be key switching and routing components in future wavelength-division multiplexed (WDM) photonic transport networks [1-4]. Important functions of OXC’s are that they allow optical networks to be reconfigurable on a wavelength-by-wavelength basis to match traffic demand, to avoid network congestion, and to restore the network from failures [1-4].
Stable Wavelength Cell Switching with Tunable DBR-LD Employing Shadow Tuning Technique
Authors: Kato T. , Takeshita H. , Takahashi S. , Henmi N.
Published: February 2023

Stable wavelength cell switching operation with tunable DBR-LD has been demonstrated employing novel shadow tuning technique, in which active region injection current is reduced below threshold before changing injection current into DBR region.
All-Optical Wavelength Conversion Between 1.3μm and 1.55μm in a Novel Nonlinear Fiber Loop Mirror
Authors: Zhao Y. , Shu C.
Published: February 2023

Recently, signal conversion from 1.5 to 1.3 μm has been demonsitrated experimentally by designing special loop fibers to reduce group-velocity mismatch [1], splicing alternating segments of different kinds of fibers to arrive at average group-velocity matching [2], and delaying two counterpropagating control beams to realize walk-off balance [3]. In the wavelength conversion, the control on the shape and size of the switching window is very important because it determines the performances of the converter such as timing jitter, speed of conversion, and the shape and width of the signal output. Here we propose and theoretically analyze a novel nonlinear fiber loop mirror (NFLM) [4, 5] wavelength converter. The characteristics of the switching window can be controlled by adjusting the opposite group-velocity delays in the standard single mode fiber (SMF) and the dispersion shift fiber (DSF) as well as the width of the control pulse. This NFLM has two output ports providing pulses with different profiles and has the flexibility to be adopted in a variety of system applications.
Room Temperature Persistent Spectral Hole Burning in Distributions of Optical Cavities: A Simple Fabry-Perot Model
Authors: Pack Dee William , Arnold Steve
Published: February 2023

Efforts to create materials in which to burn holes at higher temperatures face an inherent contradiction: the need for inhomogeneous line broadening from host-guest interactions, vs. the desire to limit the homogeneous line broadening from thermal fluctuations of host-guest interactions (i.e. phonon broadening). A different approach to the question of how to burn holes at high temperatures was recently conceived and experimentally confirmed.1 This approach relies on using distributions of chromophore-doped optical cavities as the hole burning medium. The effect was recently observed in dye-doped micro-spheres. As a simple model illustrating the important effects characteristic to these Mie theory cavity resonances in spheres, the Fabry-Perot is treated analytically and numerically in this work.
The study of weak linear electron-phonon coupling in iron-free hemeproteins
Authors: Lin J.W-I. , Tada T. , Saikan S. , Kushida T. , Tani T.
Published: February 2023

The present interest in the PHB optical memories has motivated research into finding materials which have weak electron-phonon coupling between the guest impurity and the host system. The magnitude of the linear electron-phonon coupling strength can be obtained from the Debye- Waller factor, the relative strength of the zero-phonon line and phonon sideband of the homogeneous spectrum. The Debye-Waller factor can be determined readily in crystals; in amorphous solids, however, the large inhomogeneous spectral broadening masks the individual homogeneous spectrum. Out of the many nonlinear spectroscopic techniques, our group utilized the femtosecond accumulated photon echo technique with phase modulation1 to examine the polymer dependence of the electron-phonon coupling in amorphous dye-doped polymer systems.
Hole Burning in Long Chain Molecular Aggregates
Authors: Hirschmann R. , Friedrich J.
Published: February 2023

The salts of pseudoisocyanine (PIC) have very specific optical properties. Under certain conditions (concentration, temperature) the PIC-molecules form linear aggregates in solution. Since the coupling between the molecules comprising the aggregate is very strong, the excited states are delocalized over a large range. A coherence length on the order of 1000 Å is not uncommon. These excitonic states carry momentum and, hence, the physics of these systems shows novel phenomena as compared to small probe systems. Such phenomena are , for instance, extreme motional narrowing of inhomogeneous line broadening and a very specific temperature dependence of the homogeneous width due to exciton-phonon-scattering processes in which both, energy as well as momentum, have to be conserved.
Kinetics of Hole Burning in Inhomogeneously Broadened Spectra: the Origin of Nonexponentiality and Problem of Burning Efficiency Dispersion
Authors: Al’shits E.I. , Kharlamov B.M. , Ulitsky N.I.
Published: February 2023

High inhomogeneous broadening of impurity spectra in amorphous media reflects one type of dispersion, characteristic for disordered systems: dispersion of electronic transition frequency. In principle, there can exist a pronounced dispersion of other parameters: homogeneous line width (Γ), Debay-Waller factor (α), hole burning efficiency (ϕ), etc. The problem of the burning efficiency dispersion (BED) was extensively discussed in the recent years ([1-6] and references therein). The nonexponentiality of the burning kinetics was treated in some publications [1-3,6] as an evidence of such dispersion. But burning kinetics is always nonexponential in strongly inhomogeneously broadened systems, if a burning laser line width Δνl is much less then Γ. That was found experimentally and treated theoretically in one of the first publications on a hole burning [7] (see, also [8]). All other sources of the nonexponentiality are, in fact, additional to this one. So, it’s not easy to attain experimentally the BED parameters on such background. The procedure of a numerical fit ting of the burning kinetic with BED, developed in [4,5], is correct, but it looks unreliable due to many fitting parameters.
Applications of spectral hole-burning spectroscopies to the excited electronic states and transport dynamics of photosynthetic units
Authors: Small G. J.
Published: February 2023

Hole-burning methodologies suitable for the study of excited electronic state structure, energy and electron transfer dynamics, electron-phonon coupling, and heterogeneity of photosynthetic units are discussed.
Microwave-Induced Hole Burning of the 638 Nm Zero-Phonon Transition and Frequency-Dependent Dephasing of the N-V Center in Diamond
Authors: Glasbeek Max , van Oort Eric
Published: February 2023

In recent years the microscopic description of inhomogeneous broadening of electronic transitions of chromophores in crystals and glasses has attracted much interest [1–3]. In the phenomenological model proposed by Selzer [1], it is assumed that the energies of the initial and final states involved in the optical transition exhibit a one-to-one correlation. In an alternative approach by Lee et al [2], the two states are considered as completely uncorrelated. Very recently, a more general microscopic theory has been presented by Laird and Skinner [3]. In the latter theory the aforementioned models are obtained as limiting cases. So far relatively few experiments have been reported which focus on the origin of inhomogeneous broadening.
Spectral Diffusion of Optical Transitions in Doped Polymer Glasses below 1° K
Authors: Haarer D. , Müller K.-P.
Published: February 2023

Photochemical and photophysical hole burning is a well established technique for eliminating the large inhomogeneous broadening of electronic transitions, which dominates the optical spectroscopy of amorphous solids. With the possibility of measuring the quasi-homogeneuos width Γ
qh
of electronic transitions, dye molecules can be used as probes for dynamical processes in amorphous solids [1][2]. The temperature dependence of the electronic linewidth of a given dye molecule in a crystalline lattice as compared to its linewidth in an amorphous solid shows large differences in both, its absolute value and its broadening behavior. This is due to the different origin of the dominant line broadening mechanisms: Interaction with phonons in a crystalline host and with two level systems (TLS) in an amorphous solid.
Frequency Dependence of IR Radiation-Induced Spectral Diffusion in Hole-Burning Systems
Authors: Richter W. , Lieberth M. , Haarer D.
Published: February 2023

Persistent spectral holes burnt in polymeric matrices such as polyethylene (PE) and polymethylmethacrylate (PMMA), doped with metal-free phthalocyanine (H2Pc), show infrared (IR) light-induced spectral diffusion (Fig. 1) /1,2/.
Molecular Computing
Authors: Wild Urs P. , Renn Alois
Published: February 2023

Each dye molecule embedded in an amorphous material such as a a polymer host experiences a specific molecular environment which strongly influences its electronic transition energies. At low temperatures the different microenvironments result in an inhomogeneously broadened absorption band. The invention of the laser brought new spectroscopic techniques based on energy selection, such as fluorescence line narrowing and spectral hole-burning [1]. These techniques enable convenient addressing of thousands of molecular subsets selected by their transition energy.
Spectral hole burning between 2 K and room temperature in Sm2+ doped substitutionally disordered microcrystals
Authors: Bilmers R. , Davis J. , Squicciarini M.
Published: February 2023

Filter operation is achieved by depleting the ground state population of molecules whose local environments are within the bandwith of the hole-burning pump laser.
Persistent Hole Burning Study of Core Antenna of Photosystem II
Authors: Vacha M. , Adamec F. , Ambroz M. , Dian J. , Nedbal L. , Hala J.
Published: February 2023

The application of hole burning spectroscopy (HB) in the study of photosynthetic systems offers an independent method for determining excited state lifetimes of particular chromophores. The rate constants of excitation energy transfer (EET) in photosynthetic antennae can be directly determined by time resolved fluorescence spectroscopy. For most bacterial and higher plants antennae is of the order of 10-12 s–1 [1]. Efficient EET in pigment-protein complexes causes significant shortening (three orders of magnitude) of the excited state lifetimes T1 in comparison with isolated pigments.
Spectral Hole Burning: Dynamical Approach to Spectral Diffusion Problem
Authors: Osad'ko I. S.
Published: February 2023

Herzog and Hahn [1] and Portis [2] while striding magnetic resonance in 1956 found hole broadening with time. This phenomenon was called ”spectral diffusion”.
Preparation and properties of sol-gel thin films with Porphins
Authors: Inoue Hiroyuki , Iwamoto Takashi , Makishima Akio , Ikemoto Makoto , Horie Kazuyuki
Published: February 2023

Recently the sol-gel process for preparing amorphous materials has been studied. The low processing temperatures enable us to dope the gel with functional organic molecules. Such molecules have poor thermal stability and cannot be included in traditional oxide glasses. Avnir et al.1,2) have been reported the preparation and optical properties of amorphous silica doped with rhodamine 6G and pyrene. Makishima and Tani3,4) have doped one with 1,4-dihydr-oxy-9,10-anthraquinone (DAQ) and showed photochemical hole burning (PHB) at 4.8 K. They have also demonstrated that other organic molecules can be successfully incorporated into sol-gel matrices. The number of potential applications of such materials is expected to be substantial.
Optimized Read/Write Conditions of PHB Memory
Authors: Murase Norio , Horie Kazuyuki
Published: February 2023

PHB memory has been a good candidate for a future ultra high density memory for these ten years. This PHB memory is considered to realize the recording density of 1000 times higher than conventional optical memories because it can store wavelength-multiplicitically 1000 bits in a 1-μm diameter recording spot. But not so many researchers are working on PHB memory compared to the number of researchers wrestling with realization of higher recording density of other types of memory such as magnetic or optical ones. One of the reasons is based on the doubt whether high speed readout is possible in such a high density recording in 1-μm diameter spot. Therefore one of the most important research on PHB memory is the estimation of degree of coexistence between high recording density and high speed readout.
Relationship between soft X-ray reflectance and structural parameters of nanometer-period multilayers for X-ray mirrors
Authors: Houdy Philippe , Boher Pierre
Published: February 2023

Multilayers alternating materials at atomic scale have been deposited, using UHV diode rf sputtering, to be used as soft X-ray mirrors [1,2,3,4]. We have investigated the relationship between the stack performances (reflectivity, selectivity) and the structural chara cteristics of the stacks. The use of graphite instead of amorphous carbon in Ni/C multilayers results in an increase of the performances as well as cooling the sample during the deposition. A similar effect is observed in W/BN multilayers introducing nitrogen during the growth to saturate the nitride. In the case of Si/SiN stacks, narrow Bragg peaks and a higher reflectivity are obtained anealing the samples up to 800°C. At least, a comparison is made between Mo/Si and Co/Si multilayers in order to show the importance of interface compound formation.
Modeling of x-ray diffraction by multilayer mirrors, gratings and zone plates
Authors: Sammar A. , Pardo B. , André J-M.
Published: February 2023

The diffraction problem consists in solving the Helmholtz equation for the tangential electric field component φ in the TE polarization case. The equation is: where k is the wavenumber, ε(R) is the complex dielectric constant and R is the position vector.
Ion-Assisted Sputter Deposition of Mo-Si Multilayers
Authors: Vernon S.P. , Stearns D.G. , Rosen R.S.
Published: February 2023

Mo-Si multilayer (ML) structures fabricated using DC magnetron sputtering in an Ar plasma show a transition from layer to columnar growth as the deposition pressure is increased above ~1 mTorr. The dominant effect of the increased deposition pressure is the increased thermalization of Ar neutrals, reflected in charge exhange collisions with the sputtering target, striking the substrate surface. At high deposition pressure there is less energy deposited at the substrate surface which, in turn, modifies the adatom mobility. These effects markedly impact the layer morphology. The layers are observed to have significantly increased roughness at higher deposition pressures. Consequently, the x-ray optical properties of the ML coatings are strongly effected. The measured normal incidence reflectivity at 130 Å decreases from ~60% to 14% as the deposition pressure is raised from 2.5 to 10 mTorr [1].
Image Quality and Scattering by Multilayer X-Ray Mirrors and its Implication for the Fabrication of Diffraction Limited Large X-Ray Optics
Authors: Spiller Eberhard , Stearns Daniel
Published: February 2023

Roughness of the boundaries presents a severe limitation for the performance of multilayer x-ray mirrors with small periods Λ < 50Å, and makes it difficult to produce efficient multilayers with periods approaching the size of the atoms in the coating. Reflectivities are reduced by a large factor from the theoretical smooth boundary value, for example nearly a factor 10 for a coating with period Λ = 30Å. If all the loss in reflectivity would appear as scattered light within the field of view of an instrument, one would not be able to obtain high contrast images of extended objects; each image element would be surrounded by a halo of scattered light of much higher total intensity.
Thermal Stability of Mo-based Multilayers Fabricated by rf Sputtering
Authors: Ishii Yoshikazu , Takenaka Hisataka , Kawamura Tomoaki , Kinoshita Hiroo
Published: February 2023

Mo-based periodic multilayers such as Mo/Si and Mo/B4C show great promise as reflectors for soft x-ray reduction lithography 1-3). The thermal stability of multilayers is one of the most important factors for ensuring the reliable performance. The Mo/Si and Mo/B4C multilayers show high reflectivity in the 8 nm - 15 nm region at normal incidence. The purpose of this paper is to present the resulting changes of layered and crystal structures of the Mo/Si and Mo/B4C multilayers upon thermal annealing.
Effects of Fresnel Fringes on TEM Images of Interfaces in X-Ray Multilayers
Authors: Nguyen Tai D. , O'Keefe Michael A. , Kilaas Roar , Gronsky Ronald , Kortright Jeffrey B.
Published: February 2023

Cross-sectional High-Resolution Transmission Electron Microscopy (HRTEM) has been widely used to examine the structure and morphology at multilayer interfaces at an atomic scale. Assessment of the interfacial structures quantitatively from these TEM images however is difficult due to the Fresnel fringe effects, which produce different apparent structures with defocus values in the images. These fringes result from the electrons experiencing an abrupt change in the scattering potential parallel to the electron beam path. Imaging of multilayers in cross-section, in which the electrons travel parallel to the interfaces between the two layer materials, always results in such fringes. X-ray multilayers having alternating layers of very different atomic numbers or scattering powers are more prone to these fringes than the heterostructures having less contrast layers. The visibility of the fringes increases with increasing defocus away from the minimum contrast, while optimum resolution in bright-field imaging is obtained at the Scherzer defocus, which is about 100 nm from the minimum contrast for most high resolution microscopes. Fresnel fringes are thus present when imaging at optimum defocus. The effects of these fringes have been commonly overlooked in efforts of making quantitative interpretation of interfacial profiles. They however have also been employed to characterize the structures and compositional roughness at interfaces.1-3 In this report, we present the observations of the Fresnel fringes in nanometer period Mo/Si, W/C, and WC/C multilayers in through-focus-series TEM images. Calculation of the Fresnel fringes of a Mo/Si multilayer using charge density approximation is used to illustrate the characteristics of the fringes from different interfacial structures.
Synchrotron Study of Roughness in Fe-Cr Multilayers
Authors: Clemens B.M. , Payne A.P. , Brennan S.
Published: February 2023

Many advances in the characterization of roughness in artificially layered structures have grown out of interest in their x-ray optical properties. In the present work we apply these techniques to a different application of layered media: magnetic multilayers. Recent reports have shown that the antiferromagnetic order and giant magnetoresistance in layered magnetic materials are mediated by interface quality and roughness, and several reports claim layer roughness enhances giant magnetoresistance. The objective of the current work is to characterize interface roughness and correlate it to the magnetic properties in these materials. We have fabricated structurally distinct Fe/Cr layered structures and examined both the exchange coupling and electrical transport properties. We correlate this with quantitative measurements of the character and magnitude of the structural perturbations.
Mosaic Reflectivity of X-ray Multilayer Structures
Authors: Christensen F.E. , Schnopper H.W.
Published: February 2023

Mosaic reflectivity from multilayer structures has previously been detected1) but only in a limited angular range close to the Bragg angle (θB) and only at a single energy. In this paper, a systematic study of the mosaic reflectivity is performed at five line energies (B-Kα (0.183 keV), Cr-Lα (0.573 keV), Ni-Lα (0.852 keV), Pd-Lα (2.838 keV), Cu-Kα (8.048 keV)) for a series of Ni/C multilayers with similar d-spacings and similar ratio between Ni-content and C-content but different deposition methods. The mosaic reflectivity is measured in the complete angular range from zero to 2 θB around the first order Bragg peak. Several interesting and novel effects are revealed. First of all, it is observed that the mosaic reflectivity increases linearly as the angle of incidence is decreased. Secondly, the mosaic reflectivity is observed to decrease sharply as one enters the total reflection region. Thirdly, the mosaic reflectivity disappears completely as the angle of incidence approaches twice the Bragg angle. Finally, the mosaic reflectivity varies in a characteristic way with the energy.
Morphology of Thin Film Growth
Authors: Collins R.W. , An Ilsin , Li Y.M.
Published: February 2023

Thin films prepared by vapor deposition methods have a range of applications which demand control over the microstructural, electronic, and/or optical properties. Empirical classification schemes for the morphology of vapor-deposited thin films have been developed over the years in attempts to provide physical insights into the relationships between preparation parameters and resulting film properties.1-3 A variety of computational techniques have also been applied to model film growth and to elucidate the physical principles that account for the observed morphological development. These include continuum,4 molecular dynamics,5 Monte Carlo,6 and ballistic aggregation7 techniques. In continuum models of film growth, many authors have studied the stability of one-dimensional surface profiles in response to sinusoidal perturbations of wavelength, λr.4,8-10 Effects of finite atomic size4 and shadowing by asperities8 have been proposed to enhance the perturbations, whereas adatom surface diffusion damps them. A smooth profile can be regained for λr<λo, where λo is the adatom diffusion length. When λr>λo a modulated profile develops that appears analogous to experimentally-observable columnar morphology. In the experimental situation, clustering associated with initial nucleation is the dominant surface perturbation for thin film deposition on dissimilar substrates. It is technologically important to determine and control the evolution of surface morphology with subsequent film growth. Of direct importance here is the ability to fabricate multilayered structures with atomically smooth interfaces.