bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical Add/Drop Multiplexing for Cell Switched Networks
Authors: Budman A. , Bugos A. , Schlafer J. , Eichen E.
Published: February 2023

Very high-speed optical networks with fixed-length cells at the physical layer, form the basis for a number of promising network architectures that have the potential to provide voice, data, and video services; asynchronous transfer mode (ATM) switching and the distributed queue dual bus (DQDB) are important examples of current fixed cell length network implementations. While these networks use the optical link to provide connectivity between nodes, with all switching being performed electronically, it is interesting to consider derivative networks that use optical switching (in conjunction with electronic switching) to improve performance. In this paper, we discuss the experimental and theoretical performance (bit error ratio, insertion loss, clock recovery, and jitter) of one such network in which fixed-length optical cells are inserted or removed from a ring or bus. Add/drop multiplexing in the optical domain [1-5] removes the requirement for optoelectronic regeneration, and store and forward of data, at every node in a network; it thus reduces latency, and is synergistic with the introduction of optical amplifiers into wide area and metropolitan area networks. Moreover, the physical layer protocol described in this paper avoids the electronic bottleneck associated with header processing at each node, and thus may lead to networks in which the data transfer rate approaches the (≈10 Gb/s) link transmission rates that can be obtained easily using conventional lightwave technology.
Experimental Results for Fast, High-Capacity Optical Switching Architectures
Authors: Moss C. J. , St. Ville L. J. , Man K. S. , Burnett I. M.
Published: February 2023

With the trends towards provision of broadband services, there will be an increasing requirement for high throughput and capacity in switch fabrics. Capacity gains can be achieved through exploiting the spectral bandwidth of optical switches. Additionally, the time and space domain can be exploited to give multidimensional switching[1]. Applications for such flexible switching lie in signal processing or fast-switching within the telecommunications network. Recently, interest has been growing in packet-based systems such as ATM. These systems require the header content of the cells to be interpreted, and used to route the cells. The control functions of such systems are best implemented using electronics, but optical switching can provide a high capacity and flexible interconnection medium.
Time Domain Approach for Avoiding Crosstalk in MINs
Authors: Qiao Chunming , Melhem Rami , Chiarulli Donald , Levitan Steven
Published: February 2023

Network dilation is a space domain approach for avoiding crosstalk introduced by optical switches. This paper proposes a time domain approach for avoiding crosstalk without dilating a network. While network dilation trades space for crosstalk-free realizations of permutations, the time domain approach trades time. Using the lime domain approach, permutations realizable in one pass in a dilated network require at least two passes in an undilated network without crosstalk. In this paper, we show that more permutations can be realized in an undilated network in two passes without crosstalk than in a dilated network in one pass. We also present simulation results for the number of passes needed to establish a set of arbitrary connections without crosstalk in either a dilated or an undilated network. Our results demonstrate the improvement in space-time tradeoffs due to the time domain approach.
Turnover-Type Free-Space Multichannel Optical Switch
Authors: Sakano Toshikazu , Noguchi Kazuhiro
Published: February 2023

A novel free-space multichannel optical switch that is suitable for intra-board chip-to-chip interconnects is proposed. A 64×64 switch is fabricated and demonstrated.
Resonant III-V Semiconductor Layer and a Grating Coupler Integrated in a Waveguide Modulator for Far-Infrared Light
Authors: Stiens J. , De Tandt C. , Ranson W. , Vounckx R. , Veretennicoff I. , Borghs G. , Moerman I. , Demeester P.
Published: February 2023

The influence of a resonant plasma layer on the cut-off conditions in III-V semiconductor waveguides is calculated. Coupling with a grating coupler will be discussed.
Demonstration of a Polarization Rotation Gate in GaAs/AlGaAs MQW Waveguide
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. , Andreakis N. C. , Caneau C.
Published: February 2023

Femtosecond optical switching is demonstrated in a nonlinear semiconductor birefringent waveguide. Optically induced polarization rotation increases the normalised gate transmission by a factor of 44.
Monolithic Integration of GaAs/AlGaAs Multiple Quantum Well Modulators and Silicon Metal-Oxide-Semiconductor Transistors
Authors: Goossen K. W. , Walker J. A. , Cunningham J. E. , Jan W. Y. , Miller D. A. B. , Tewksbury S. K. , Hornak L. A.
Published: February 2023

We demonstrate coexisting operation of a GaAs/AlGaAs multiple quantum
well modulator and a submicron gate length metal-oxide-semiconductor
transistor fabricated on the same chip, for applications in optical
interconnects.
Recent Advances in Planar Lightwave Functional Devices
Authors: Jinguji Kaname , Takiguchi Koichi , Kawachi Masao
Published: February 2023

Optical frequency-division-multiplexing (FDM) systems have been widely studied in order to achieve large-capacity optical networks. The key components in this field are optical functional devices such as multi- frequency-channel selectors[1] and band-pass optical filters. Recently, we have developed a circuit synthesis algorithm[2] by analogy with electrical digital filters. We first briefly review the evolution of silica-based planar lightwave circuits (PLCs)[3]. Then we describe the new generation of PLCs, including programmable optical filters[4], designed using the synthesis algorithm.
Evolution of Fiber Arrays for Free Space Interconnect Applications
Authors: Basavanhally Nagesh , Borutta Richard , Crisci Randall , Nijander Casimir , Watkins Laurence
Published: February 2023

Photonics technology involving parallel processing architecture is becoming extremently important for large scale information movement. The obvious reasons are high bandwidth of optical media, the lack of light beam interference and the possibility of high density interconnections. Free space optical interconnection [1] [2] [3] offers the potential for large number of interconnections. Such free space interconnect schemes are being considered for large VLSI systems and photonic switching systems. These systems require fiber arrays for bringing in and taking out optical signals from the computing or switching environment. The positioning accuracies of the fibers in such arrays vary from one to ten micrometers (microns) depending on the systems’ architecture. In this paper, we will present the opto-mechanical challenges that are presented during design and fabrication of 2-D fiber input array, and alignment and attachment of microlens arrays to fiber bundle.
Optical Beam Routing through Time-Domain Spatial-Spectral Filtering
Authors: Babbitt W. R. , Mossberg T. W.
Published: February 2023

Recent years have seen the development of a variety of techniques for the storage and processing of optical data streams in materials with [1-10] and without [11-12] intrinsic frequency selectivity. These techniques are characterized by very high bandwidth and relatively large time-bandwidth product. It is known, that the optical processes responsible for the storage and/or processing of temporal waveform data frequently also lead to the storage of spatial waveform information [13,14]. It has been demonstrated, for example, that sequences of images can be stored. [5,7,8] An area that is relatively unexplored, however, relates to the possible interactions between stored temporal and spatial information. We explore one example of how the temporal and spatial information stored within a material can interact and lead to a novel functionality, i. e. the passive routing of optical beams along one of many possible temporally encoded directions.
Multi-functional Surface-Emitting Laser-Based Integrated Photonic/Optoelectronic Switch For Parallel High-Speed Optical Interconnects
Authors: Lu Y. C. , Cheng Julian , Zolper J. C. , Klem J.
Published: February 2023

The monolithic integration of vertical-cavity surface-emitting lasers (VCSELs) with active electronic devices combines the optical source array and its driver circuits into a single IC technology, which is usefill for parallel high-speed optical interconnects. Another motive for the integration of VCSELs with high speed electronics is to provide an optical switching network with a simple optoelectronic interface that allows individual electronic computer processors to communicate with each other through parallel optical channels. A dynamically reconfigurable optical switching network1-2 can simultaneously route optical data between many different electronic processors as they perform parallel processing sequences using shared resources. Each switch of the network must provide an optical link to all the other nodes, as well as an optical ⟺ electrical interface to an electronic processor. Each switch must thus perform both the optical and optoelectronic switching functions in order to convert data between various combinations of electrical and optical input/output (I/O) formats.
Gigabit per second switching of smart pixel receiver-transmitter pairs
Authors: Livescu G. , Chirovsky L.M.F. , Mullally T. , Ron Arza
Published: February 2023

Smart pixels are opto-electronic circuits with optical input/output and electronic logic circuits for complex functionality [1]. Arrays of smart pixels can control two dimensional arrays of light beams in high speed, high throughput free space photonic switching systems [2]. An example are the 4x4 arrays of 2x1 embedded control routing nodes, based on GaAs/AlGaAs field-effect-transistor self-electrooptic-effect device (FET-SEED) technology [3], recently used in a five stage switching system [4]. Although this system was operated at 155Mbit/s only, the speeds of smart pixels can be made much higher. One way to achieve increased speeds is by addition of gain stages and the use of larger FETs. However, this makes the receivers and transmitters larger and more dissipative. Another way to increase the switching speed is to use short pulses as optical inputs, which, according to theory [5], considerably reduces the switching time of the receivers. Simple receivers have, indeed, been demonstrated to operate up to 1Gbit/s [6], but receiver-transmitter pairs could only operate up to 650Mbit/s [7]. The speed of the pair was limited by the performance of the transmitter used, which consisted of a FET inverter driving the common node of two modulators connected in series. One can make a faster transmitter by eliminating the load FET and one of the modulators, thus reducing the capacitance and increasing the effective charging current of the modulator. With such a transmitter, and the use of mode-locked pulses in the AROEBICS (Asynchronous Reset On Every Bit for Input Contentionless Switching) method [8], 200ps switching times were recently obtained [9,10]. This result indicated that smart pixels containing this transmitter should be capable of operating in the GHz range. In the present work we use trains of mode-locked laser pulses separated by 1ns to demonstrate the 1GHz operation of a receiver-transmitter pair.
Distributed Forward- and Backward-Coupling Laser: Novel Laser Diode for Wide Wavelength Tuning
Authors: Sato Kenji , Nakano Yoshiaki , Tada Kunio
Published: February 2023

Wavelength tunable lasers are required in the wavelength-division-multiplexed (WDM) photonic switching networks. Over the past several years, both continuously [1] and discontinuously [2-4] tunable lasers have been intensively studied. The latter ones are more feasible when over 20 nm tuning ranges are demanded.
A Proposal and its Implementation Scheme of an Optical Network Management System
Authors: Shiragaki Tatsuya , Henmi Naoya , Fujiwara Masahiko
Published: February 2023

Optical networks on which signals are routed and switched optically, are indispensable for achieving future large capacity and flexible communication networks. Some demonstration experiments have been carried out to show the feasibility of optical networks [1]-[4]. One of the most important issues in developing such networks is a network Operation and Maintenance (OAM) system. The present networks utilize an OAM system based on the SDH/SONET, in which OAM information is embedded in synchronous frames. Since, in the optical networks, some signals go through several nodes without any O/E and E/O conversions, OAM information cannot be obtained based on conventional schemes. An OAM implementation technology for optical networks should be put together, as some papers have pointed out [5],[6]. This paper proposes an OAM concept for optical networks. An implementation scheme for the concept is also proposed, and its feasibility is theoretically confirmed.
Photonics and ATM Switching
Authors: Dupraz Jacques
Published: February 2023

ATM in switching and optics in transmission are the key technologies of future broadband networks. This paper discusses the problems associated with the introduction of photonics in ATM switching from a technical viewpoint.
An Efficient Signal Distinction Scheme for Large-scale Free-space Optical Networks Using Genetic Algorithms
Authors: Louri Ahmed , Sung Hongki , Moon Yoonkeon , Zeigler Bernard P.
Published: February 2023

Free-space optical interconnection networks can be classified into two types, space variant and space invariant, according to the degree of space variance [1]. The degree of space variance determines the network’s complexity and regularity. A totally space variant network allows a completely arbitrary interconnection between nodes, whereas a totally space invariant network has a definite, regular structure with all the nodes having the same connection patterns. In terms of physical implementations, the degree of space variance can be interpreted as the degree of sharing beam steering optics among the nodes of a given network. In other words, all nodes in a totally space-invariant network can share a single beam steering optics (considering multiple fanouts as one steering optics) to realize the given network topology, whereas, in a totally space variant network, each node requires a distinct beam steering optics. This is one of the reasons why space variant networks require complex optical implementations that often result in low interconnection density and high cost.
Transmission Experiments on Fully Packaged 4×4 Semiconductor Optical Amplifier Gate Switch Matrix
Authors: Larsen Claus Popp , Almström Erland , van Berlo Wim , Falk Jan-Erik , Testa Fransesco , Gillner Lars , Gustavsson Mats
Published: February 2023

It is today commonly acknowledged that the optical switch will be a key component in future optical communications networks [1,2,3]. Apart from requirements such as high flexibility and transparency to bit rate and format, optical switches must be able to support wavelength division multiplexed (WDM) networks and already existing components as especially erbium doped fibre amplifiers (EDFA’s). Several designs have been suggested and implemented including both lithium-niobate [4] and semiconductor based [5] devices. Among the latter, loss-compensating components [6,7] are believed to be advantegeous, since the switch architectures will probably get rather extended. The main disadvantage compared to switches without amplification is that a limited dynamic range is obtained due to the semiconductor gain medium. The switch evaluated here (see fig 1) is a monolithic strictly non-blocking device based on semiconductor optical amplifier (SOA) gates in InGaAsP/InP, operated in the 1550 nm window [8]. Publications of optical switches have so far mainly dealt with unpackaged components. Performance has often been measured with a cw source as to achieve gain optimisation. In this paper, extensive bit error rate (BER) measurements on fully packaged InP switches are presented concerning dynamic range and dependence upon polarisation of the incoming signal. The system has been optimised for low BER rather than maximum gain. Furthermore, cascading of several switches and a WDM experiment demonstrate the usefulness of this component in future optical WDM networks, and theoretical simulations investigate dependence of reflections and bit rate.
Vertical Cavity X-Modulators
Authors: Trezza J. A. , Powell J. , Morf M. , Harris J. S.
Published: February 2023

Recently, we have experimentally developed two types of ideal optoelectronic switches using Fabry-Perot vertical, III-V semiconductor structures. Zero chirp reflectivity modulators operate as pure optical amplitude switches;1 vertical cavity phase flip modulators (VCPPM) operate as pure optical phase switches.2 The later display large intensity output in both of the device’s states and switching occurrs by altering phase between 0° and 180°. In this work we describe a photon conserving, reversible intensity switch. In this device, known as an X-modulator, the incident power is either transmitted through or reflected from the device. Reversibility indicates that the device is designed so that the outputs for light incident from both the top and bottom of the structure are nearly identical. The device ideally does not modify total amplitude or phase, but merely routes incident photons. Thus the X-modulator provides the third of the three desirable optical modulators: amplitude modulator, phase modulator, direction modulator. By being both conservative and reversible, the device is uniquely capable of performing complex optical switching, routing, and logic.3 The device is essentially a vertical cavity, electro-optical realization of an X-gate (sometimes referred to as a Fredkin Gate) which is a primitive structure into which all logic functions can be decomposed. The first experimental device, when switched with an applied bias of 40V, modulates from (T ~ 60%, R~ 6%) to (T ~ 6%, R~ 60%). We will discuss individual device design including the optimization of the device parameter space: lower voltage, optical bandwidth, modulation ratio, insertion loss, and how to match these devices to electronics. In addition, theoretical and experimental results of stacked devices and the use of graded buffers to reduce electric field requirements will be explained as will issues such as device crosstalk in cross bar switches.
The role of photonic switching in future high capacity telecommunication networks
Authors: Nilsson Olle
Published: February 2023

The role of photonic switching in future telecommunications has been the subject of intense research and discussions ever since the realisation in the early eighties that fiber optics could furnish virtually limitless broadband transmission. The basic idea is that, eventually, one will face an electronic bottle neck when it comes to switching the predicted enormous bitstreams and that photonic switching may then offer a solution.
The RACE Multi-Wavelength Transport Network Project: Results and Conclusions
Authors: Hill Goff
Published: February 2023

The RACE Multi-Wavelength Transport Network project (MWTN) began in January 1992 with 10 partners including operators, manufacturers and universities (Fig. 1) with completion scheduled for December 1995. The overall goals are to demonstrate the feasibility of an optical network layer that is transparent to signal bit rate and format and to identify evolutionary routes and standards. From an operators viewpoint, these attractive features will provide increased flexibility to carry a wide range of future services. The network approach is based on wavelength routing and uses optical amplifiers, WDM transmission and space switching [1,2]. The project has three key themes: the development of preferred technologies, practical demonstrations of multi-wavelength networking and the application of design and evaluation tools to support the technology development and demonstration activities.
Free-Space Optical Sliding Banyan Network
Authors: Haney Michael W. , Christensen Marc P. , Levy James J.
Published: February 2023

There is an ever increasing demand for high throughput, cost effective, broadband data switching networks, as demonstrated by the explosive growth in the Asynchronous Transfer Mode (ATM) equipment industry. Future networks must handle thousands of high bandwidth channels, implying an aggregate capacity in the terabit/second regime [1]. These requirements will exceed the ability of VLSI based switching technology.
Wavelength conversion devices and applications
Authors: Mikkelsen B. , Durhuus T. , Joergensen C. , Danielsen S.L. , Pedersen R.J.S. , Stubkjaer K.E.
Published: February 2023

Implementation of simple wavelength converters can be considered an enabling technology for taking the full advantage of the wavelength dimension in wavelength division multiplexed (WDM) networks [1-2]. Therefore, much attention has been devoted to the realisation of all-optical wavelength converters relying on mechanisms such as cross-gain modulation (XGM) and cross-phase modulation (XPM) in semiconductor optical amplifiers (SOAs) [3-6], optical modulation of lasers [7-9] and four-wave-mixing in fibers and SOAs [10-11]. In this paper, applications as well as desired features of wavelength converters are discussed. Additionally, different methods for wavelength conversion will be surveyed with emphasis on all-optical wavelength conversion by XGM and XPM in SOAs.
Digital Thermo-Optic Switch Formed Using Silicone Resin
Authors: Watanabe Toshio , Ooba Naoki , Hida Yasuhiro , Hayashida Shoichi , Kurihara Takashi , Imamura Saburo
Published: February 2023

A digital thermo-optic switch formed using silicone resin exhibits an insertion loss of <2.5 dB, an extinction ratio of >30 dB at 1.55 μm, and operates even at 80 °C.
Towards High-Performance, Low-Cost Optical Integrated Components for Fiber-To-The-Home Systems: Roles and Prospects of Integrated Optics and Optolectronic Components
Authors: Yoshida Junichi
Published: February 2023

Optical devices utilizing PLC optical hybrid integration platform technology and InP-based monolithically integrated waveguide devices are described as promising components for 1.3/1.5 μm- and D-WDM optical subscriber systems.
High bandwidth optical packet switching using holeburning materials at wavelengths up to 1.55 μm
Authors: Shen X. A. , Zhang Y. , Kachru R.
Published: February 2023

Packet switching has emerged as a promising networking technique capable of supporting a wide range of communications services, such as voice, video, image and data.1,2 However, implementation of this technique at optical carrier frequencies, especially at the communication wavelengths, to fully utilize the wide transmission bandwidth offered by fiber optic technologies remains a challenge. Impediments to the development includes: i) the inability to rapidly analyze temporal optical information contained in the header of each packet for efficient routing, ii) rapid data processing and buffering at the communication wavelengths. Most optical switches proposed earlier suffer from either insufficient memory capacity for storing reference information, slow processing speed for routing at required packet rates, or the requirement of wavelength conversions.
Coherent Crosstalk Issues in Photonic Switched Networks
Authors: Blumenthal Daniel J.
Published: February 2023

Coherent interference of optical signals in photonic switched networks can severely degrade performance and limit network scalability. In this talk we review the sources of coherent crosstalk and the impact on network architecture and potential solutions.
Time Dependence of Interferometric Crosstalk in All-Optical Networks
Authors: Lindunger Örjan , Almström Erland
Published: February 2023

The evolution of the optical transport network with technologies such as space and wavelength multiplex switching have introduced multi path propagation, unwanted or wanted. The unwanted propagation are often called crosstalk. When the carrier frequency of the crosstalk are within the electrical bandwidth of the main signal, fading effects similar to radio propagation occurs. These effects are often called interferometric crosstalk.
Keys To Optical Packet Switching: The ACTS KEOPS Project
Authors: Renaud Monique
Published: February 2023

The objectives of the KEOPS project as well as progress in network and system issues, dedicated components and system demonstrations will be presented.
Performance and Implementation of SLOB: a Switch with Large Optical Buffers for ATM Traffic
Authors: Hunter David K. , Cornwell W. David , Franzen Andre , Gilfedder Tim H. , Andonovic Ivan
Published: February 2023

In an output buffered optical asynchronous transfer mode (ATM) switch [1,2,3] subjected to a uniform, non-bursty load, the attainment of a cell loss of 10-11 requires a buffer depth of 55 cells [4] under a traffic load of 0.8; this doubles for a load of 0.9. For bursty loads, as would be encountered in practice with data traffic, the required buffer depth is much larger, and figures of several thousand cells have been quoted [1]. Current optical ATM experiments exhibit much lower buffer depths (e.g. 23 cells [2]) limited either by the low number of possible recirculations in a loop [2], or by the excessive hardware that would be required for larger buffer depths [3].
Demonstration of Ultrafast All-Optical Packet Routing
Authors: Glesk I. , Prucnal P. R.
Published: February 2023

Recent advances in device technologies have opened new opportunities for implementing OTDM in very high-speed long-haul transmission as well as networking. The multi-terahertz bandwidth made available with the advent of optical fibers has spurred investigation and development of transparent all-optical networks that may overcome the bandwidth bottlenecks caused by electro-optic conversion. In future fiber-optic broad-band integrated digital services networks, the large data rates in the fiber-optic transmission links as well as the large number of packets transmitted per second will place sever demands on the required transmission bandwidth and reconfiguration speed of packet switches. Although electronic switching technology has already achieved high switching speeds, it is quite possible that it will be difficult for electronic switches to match the transmission bandwidth that the fiber-optic link can provide. In today fiber-optic packet-switched networks, routing of the packets is made with opto-electronic LiNbO3 crossbar switches. Switching speed of these devices is practically limited only up to several tens of GHz.
Inhomogeneous Broadening and Persistent Spectral Hole-Burning of Divalent Samarium Ions In Alkaline Earth Metal Halides
Authors: Zhang Jiahua , Wang Xiangjun , Huang Shihua , Yu Jiaqi
Published: February 2023

Persistent spectral hole burning (PSHB) was discovered in organic molecular system in 1974[1]. Five years later, PSHB in inorganic materials was discovered in NaF by R. M. Macfarlane et al [2]. In 1985, A. Winnacker et al [3] first observed photon gated spectral hole burning in BaFCl: Sm2+ at 2K. Hole burning(HB) is useful in high resolution spectroscopy. It is also of crucial importance for the application to frequency domain optical storage. The storage density is proportional to the ratio of inhomogeneous linewidth(Γi) to the homogeneous linewidth(Γh), N(= Γi/Γh). The inhomogeneous linewidth of 5D0-TF0 transition of Sm2+ is 16GHz and the hole width is 25MHz in BaFCl at 2K[3]. For this material, the inhomogeneous linewidth changes only moderately with the temperature; On the other hand, the homogeneous linewidth increases rapidly as the temperature rises. Then, a small value of N(~2) can be estimated when HB temperature is raised to 77K. That means, it is difficult to burn a hloe in the inhomogeneous line in BaFCl:Sm2+ at 77K. To maintain a reasonable storage capacity or to study HB at a quite high temperature, a large inhomogeneous linewidth is in great request.
Room-Temperature Persistent Spectral Hole Burning in Sm2+:SrFCl0.5Br0.5
Authors: Jaaniso R. , Bill H.
Published: February 2023

We report the first observation of spectral hole burning in the spectra of impurity centers at room temperature. The persistent holes are burned in the 5D17F0 (632 nm) and 5D0-7F0 (690 nm) transitions of Sm2+ ions in the title compound.
Frequency - Domain Measurements of Spectral Hole Patterns Burned with Phase - Coherent Pulses
Authors: Jefferson C. Michael , Meixner Alfred J.
Published: February 2023

Several investigations have shown that in some systems stimulated photon echoes may be obtained over times much longer than the excited state relaxation time T11,2. It has been claimed that the mechanism for this anomalously long storage time is the formation of a frequency dependent modulation of the ground state population which persists because of spectral hole-burning1. Such a population grating produced by coherent multipulse excitation and spectral hole-burning has been measured only in a few cases3.
Hydrogen Bonds in a Polymer Investigated by Picosecond Infrared Hole Burning
Authors: Graener H.
Published: February 2023

In the past spectral hole burning was intensively investigated for dye molecules in solid matrices. The long-lived photochemical holes at low temperature gave valuable and detailed information on the structural properties of the molecular surrounding, e.g. polymer matrices. More recently, persistent photochemical hole burning at low temperatures was extended to the infrared for smaller molecules in rare gas1 or glass matrices and to hydrogen bonded polymers.2
Persistent spectral holeburning induced by ion-tunneling in hydrogenated CaF2:Pr3+ and SrF2:Pr3+ crystals
Authors: Reeves R. J. , Macfarlane R. M.
Published: February 2023

The crystal systems of CaF2:Pr3+ and SrF2:Pr3+ into which H−, D−, or T− ions have been diffused exhibit persistent spectral holeburning when particular Pr3+ ion centers are resonantly excited.1 The H− ions replace lattice and interstitial F− ions.2 The holeburning is caused by H− (or D−, T−) ion motion in the lattice following the Pr3+ excitation and the holes have lifetimes of at least several hours at low temperatures.
Iron-free Cytochrome C and Myoglobin in Buffer Glass as Weakly-coupling Mesoscopic Molecular System: Holeburning, Absorption and Fluorescence Spectra and their Temperature Properties
Authors: Tani Toshiro , Sakakibara Youichi , Takahashi Hisao , Yamamoto Kyonosuke
Published: February 2023

Persistent spectral hole burning is a useful tool to detect zero-phonon line and phonon sideband of organic dye molecules doped in glasses and polymers, which are usually covered under inhomogeneous broadening. These observation bring us information on the electron-phonon interaction such as Debye-Waller factor a in these molecular systems. From the viewpoint of the issue of materials designing for wavelength-multiplexed optical memory and also with naive interest to obtain efficient sharp holes, we have paid much attention to the molecular systems in the category of rather weaker inter/intra-molecular coupling.
Photon Echo Decay and Optical Storage in Pr Doped YAlO3
Authors: Kröll Stefan , Kachru Ravinder
Published: February 2023

Homogeneous dephasing processes and optical storage in Pr doped YAlO3 crystals have been examined using photon echoes produced by gated continuous wave laser excitation.
Spectral diffusion decay for strongly interacting spins in glasses
Authors: Zürcher U. , Silbey R.
Published: February 2023

Thermal properties of glasses are successfully described with a model consisting of two-level systems (spins) coupled to a phonon bath [1], [2]. In most treatments, it is assumed that the spin-phonon interaction is weak. However, recent detailed examinations have revealed that this assumption is not justified [3] and that, therefore, the spin-phonon interaction is important for understanding physical properties of glassy materials [4], [5]. In this paper, we examine the implications of strong spin-phonon interaction on the spectral diffusion [6].
Solvation Effects of Organic Dyes in Polymers: Wavelength Dependence of the Stark Effect
Authors: Vauthey Eric , Holliday Keith , Wei Changjiang , Renn Alois , Wild Urs P.
Published: February 2023

The wavelength dependence of the electric field effect on holes burnt in the absorption spectrum of nile red (NR) and cresyl violet (CV) in polyvinylbutyral (PVB) and polyvinylformal (PVF) films has been investigated. The holes were detected using the holographic method [1].
Optical Spectra of Single Impurity Molecules in a Polymer: Spectral Diffusion and Persistent Spectral Hole-Burning
Authors: Basché Th. , Moerner W. E.
Published: February 2023

Recent advances in the optical detection and spectroscopy of single impurity centers in crystals has provided the possibility of obtaining information about defect-solid interactions on a truly local level. For the system composed of pentacene impurity molecules in the crystal p-terphenyl, single molecules have been studied using both absorption1 and fluorescence excitation2 techniques at liquid helium temperatures. The superior signal-to-noise of the latter technique has led to direct observations of the lifetime-limited Lorentzian homogeneous profile of a single pentacene impurity3 as well as the surprising observation of spontaneous spectral diffusion4. Spectral diffusion, or changes in the resonance frequency of an impurity molecule with time as a result of low-energy excitations (two-level system transitions (TLS)),5 is generally expected in amorphous hosts. Indeed, the presence of TLSs in amorphous solids is intimately connected with nonphotochemical mechanisms for persistent spectral hole-burning (PSHB) in amorphous materials6-8. Using perylene impurity molecules in poly(ethylene), we have observed the optical spectra of single molecules in a polymeric host for the first time. At 1.5K, individual perylene molecules show the expected spectral diffusion; moreover, we observe light-induced changes in resonance frequency, i.e., persistent spectral hole-burning, which allows one to envision optical storage on the single-molecule level.
Spectral Cain Cross Saturation and Hole-Burning in Wideband Erbium-Doped Fibre Amplifiers
Authors: Tachibana M. , Laming R.I. , Morkel P.R. , Payne D.N.
Published: February 2023

Cross saturation characteristics are investigated in broadband 1.48μm pumped and 980nm pumped, gain-shaped" EDFAs. "Gain-shaping" is shown to give a more uniform spectral gain compression on saturation. In addition room temperature spectral gain hole-burning is observed for the first time.
Persistent Spectral Hole-Burning of Pr3+ ions in (ZrO2)1−x(Y2O3)x mixed crystals
Authors: Tanaka K. , Okuno T. , Suemoto T. , Yugami H. , Ishigame M.
Published: February 2023

Many persistent spectral hole-burning (PSHB) experiments on various organic glasses and polymers doped with organic molecules reveal that the temperature dependence of the homogeneous linewidth (Γh) is T1.3 at low temperatures (0.3 K ~ 20 K) 1),2) In contrast to organic molecules, very few PSHB data exist for rare earth ions in inorganic materials while data by fluorescence line-narrowing (FLN) above ~10K are considerably accumulated 3) Macfarlane and Shelby observed PSHB in Pr3+- and Eu3+-doped silicate glasses and reported that Γh of them have a T1.0 - dependence 2),4). Similar results were obtained by Van der Zaag et al.5). In pure crystals, Γh is theoretically expected to have a T7 - dependence in the low temperature region and a T2 - dependence above the Debye temperature (Raman process) 6).
Optical Pumping Detection of Anomalous NQR Spectra of Pr3+ in Pr3+:LaF3
Authors: Wald L. L. , Hahn E.L. , Lukac M.
Published: February 2023

The nature of inhomogeneous broadening in rare earth systems plays an important role in the dynamical optical properties of ions in crystals. For this reason much of the work on the nature of the inhomogeneous broadening in rare earth doped systems has concentrated on the investigation of ion-ion interactions such as spectral transfer and up conversion processes.1,3 Variations in homogeneous optical dephasing times across the inhomogeneous optical line have also been reported.4 These studies concentrate on the variations of collective effects of ion- ion interactions at different positions in the inhomogeneous optical line in relatively heavily doped rare earth systems. We report variations in optically detected NQR (ODNQR) linewidths and shifts of Pr3+ hyperfme transitions in the optical ground state as a function of position in the inhomogeneous optical line and for satellite transitions of the 1D2-3H4 transition in lightly doped (0.5 at. %) Pr3+:LaF3.
Hole-Burning of Dye-Molecules Adsorbed on Metal Oxide Powders
Authors: Basché Th. , Bräuchle C.
Published: February 2023

First preliminary persistent spectral hole-burning (PSHB) investigations of dye-molecules adsorbed onto the disordered surfaces of metal oxide powders or porous glasses1,2,3 indicated that these systems seem to behave quite similar to doped glasses. The optical absorption is strongly inhomogeneously broadened due to the disorder of the surface and at 1.5 K holewidths in the 1 cm1 range - even an order of magnitude broader than in glasses - have been reported. In the following we will give a short summary of our latest more detailed investigations of surface adsorbed dye-molecules which on the one hand reaffirm that these systems indeed behave in many respects as 3-D disordered systems but on the other hand point to some remarkable specific features of adsorbed dye-molecules.
Error-Corrective Recall of Digital Optical Images in Neural Networks Models by Photoburning of Spectral Holes
Authors: Rebane Karl K. , Ollikainen Olavi , Rebane Alexander
Published: February 2023

The neural-network-like scheme of data storage and processing of N-bit sequences of information needs a memory of about N2 elements (interconnections). In digital auto-associative memories /1/ the useful data is presented usually as a set of S different words, v(
s
)(s= 1,…, S), each word being a sequence of N bits. Simple mathematical rule /2/, given originally by Hopfield /3/, can serve as an algorithm to calculate the values of the N2 elements of the memory matrix, T. Recall of the memory gives an output word, v(out), which results from a thresholded inner product between the interrogating input word, v(
in
) and the memory matrix.
Persistent Spectral Hole Burning Applications for Massive Optical Neural Network Computers
Authors: Henshaw Philip D. , Lis Steven A.
Published: February 2023

Neural networks require two types of operations; interconnections, which define how the output of one state affects the input of the next, and non-linear operations, which relate the inputs of a state to its output. Interconnections, which require many signals passing through the same space, are best performed with photons, which do not interact with one another. Non-linear operations require interaction (i. e., cross products) between the various inputs to a state, and are best performed with electrons, which interact strongly through their electrical charge. In a typical neural network architecture, almost all of the computation required is associated with the interconnections, and only a tiny fraction is associated with the non-linear operations (sigmoidal response or thresholding) performed at each state.
Holography in Frequency Selective Media: Hologram Phase and Causality
Authors: Bernet Stefan , Kohler Bern , Rebane Alexander , Renn Alois , Wild Urs R
Published: February 2023

Persistent spectral hole burning [1] in conjunction with holography (PSHB) opens new prospects for high density optical information storage and processing. In the holographic approach, hole burning is carried out with two -crossed coherent laser beams which bleach out a narrow frequency domain hole in an inhomogeneously broadened absorption band recording, at the same time, a spatial holographic fringe pattern. During read out of the hologram diffraction from this spatial fringe pattern occurs, and a holographic image is reconstructed, reflecting the changes of the absorption coefficient and the refractive index introduced by the spectral hole [2].
Spectral Hole-Burning Between 2 K and Room Temperature in Sm2+ Doped Substitutionally Disordered Microcrystals
Authors: Holliday Keith , Wei Changjiang , Croci Mauro , Wild Urs P.
Published: February 2023

Photon gated spectral hole-burning was first observed in a samarium doped crystal, BaFCl:Sm2+ [1]. This material was of interest to the developement of optical memories as the holes were found to be stable to room temperature thermal cycling. Holes could be burnt at liquid helium temperatures but as the temperature was raised the line quickly became homogeneously broadened. The addition of bromine to the melt succeeded in broadening the inhomogeneous linewidths to about 2 nm through substitutional disorder [2] and persistent holes were observed at 77 K [3]. Subsequently, a study of the parameters for spectral hole-burning in a BaFCl0.5Br0.5:Sm2+ crystalline powder was performed [4] and the highest temperature for which persistent hole-burning had been observed was raised to 133 K. Here we report spectral hole-burning at room temperature (figure 1) in a related compound, Sr0.5Mg0.5FCl0.5Br0.5:Sm2+.
Hole Burning of the Exciton Coupled Antenna Complex of Rhodobacter Sphaeroides
Authors: Reddy N. R. S. , Small G. J.
Published: February 2023

Efficient energy transfer in light harvesting (LH) complexes forms an important part of the photosynthetic process that results in the conversion of light energy into chemical free energy. A number of factors are important for understanding the process that directs the optical excitation to the reaction center. Included are the nature of relevant excited states of chlorophylls (e.g. localised or delocalised), bath induced mechanisms for homogeneous broadening of transitions etc. The Qy-absorption (S1) of chlorophyllic molecules in protein complexes appears as inhomogeneously broadened bands with ΓI ~ 50 - 200cm-1 at liquid helium temperatures.
Physical Optics of X-Ray Multilayer Structures
Authors: Spiller Eberhard
Published: February 2023

The paper will review the present state-of-the-art of multilayer optics. Different theories to model the performance of multilayer structures will be compared and the influence of imperfections will be discussed. Optimized coating designs for the XUV will be compared to perfect crystals, as used in x-ray diffraction and laser mirrors, as used for visible light. Practically all deposition methods have been used for the fabrication of x-ray multilayer structures and we will summarize their strengths and weaknesses. Material combinations for a specific application are first selected by the optical constants at a specific wavelength and then by the requirement that the materials chosen must form atomically abrupt, smooth and stable boundaries. Only a handful of combinations are in practical use. The limit on the performance of multilayer structures is given by absorption and by the roughness of the boundaries. The shortest practically useful multilayer period (Λ ≈ 25Å) is limited by boundary roughness and a drastic improvement at shorter periods can only be expected if we learn to place atoms by a non-random process.
Effects of Sputtering Pressure on Roughness and Resputtering of Multilayers
Authors: Hasan M.M. , Highmore R.J. , Somekh R.E.
Published: February 2023

This summary outlines studies of W-Si and Co-Cu multilayers. We recognize that W-Si is unlikely to make optimal x-ray mirrors, because Si is more strongly absorbing than, say, carbon for most radiation wavelengths, and because the known propensity of metal-silicon couples to interdiffuse to form silicides suggests that interfaces’are unlikely to be very sharp. W-Si is, though, a useful model system. A more extensive account of our work with W-Si and related systems is contained in [1]. Interfacial roughness is important in determining the properties not only of x-ray mirrors, but also of multilayer systems which exhibit so-called "giant magnetoresistance". We are using Co-Cu as a model system with which to study this phenomenon.
Stress, Morphology, and Optical Properties of Mo/Si X-Ray Multilayers
Authors: Windt D.L. , Kola R. R. , Waskiewicz W.K. , Hull R. , Griffith J. , Grigg D. A.
Published: February 2023

Due to its high X-ray reflectance (~60%) for wavelengths longer than the Si-L absorption edge near 125 Å, the Mo/Si X-ray multilayer (XML) system is now used in a diverse range of advanced applications, including soft X-ray projection lithography and X-ray astronomy. Consequently, the stability and the structural and optical properties of this system have been extensively studied [1-7]. High resolution transmission electron microscopy (HRTEM) of sputter-deposited Mo/Si XMLs reveals that the Mo layers are polycrystalline, the Si layers amorphous, and the interface region composed of an amorphous mixture of Mo and Si. Further investigations have indicated that this interlayer material is, in fact, amorphous MoSi2. Thermal anneal studies have revealed the absence of solid-state amorphization, in spite of the presence of the amorphous alloy interfacial layers. Instead, the amorphous interlayers crystallize, and growth of the crystalline product, MoSi2 proceeds in the temperature range 275-550°C. At higher temperatures (600°C), the Mo5Si3 phase appears as well. However, at lower temperatures (<200°C), no structural or optical changes have thus far been reported.
An Experimental Set-up for the Production of Large Size X-Ray Multilayer Structures
Authors: Ziegler E. , Peffen J.Ch. , Høghøj P.
Published: February 2023

Multilayer-based x-ray optical components call for heterostructures made of smooth and uniform layers with an abrupt interface, which imposes severe restrictions to the choice of materials. The multilayers have to be very uniform (1%) over the area that will be illuminated by an X-ray beam. For hard x-rays the small angle of incidence implies multilayers that are several tens of centimeter long, even when using a small d-spacing. When the beam is produced by a synchrotron storage ring source the high heat flux connected with the intense x-ray beams requires materials that are chemically very stable.
Interfacial Roughness and Interdiffusion Derived from a Comparison of the Measured and Calculated Reflectances of Mo/Si Multilayer Coatings
Authors: Seely J. F. , Kowalski M. P. , Barbee T. W. , Rife J. C. , Hunter W. R.
Published: February 2023

Mo/Si multilayer coatings were fabricated at LLNL and were characterized using the Grating/Crystal Monochromator and Reflectometer attached to the Naval Research Laboratory beamline X24C at the National Synchrotron Light Source. The reflectances were measured at several angles of incidence and for both s and p polarizations. The measured reflectances were compared to calculations that included the effects of interdiffusion layers and of roughness at each interface and that were based on Henke's optical constants.
Sputtering Deposited Ta/Si Multilayer Soft X-Ray Mirrors
Authors: Jianda Shao , Zhengxiu Fan
Published: February 2023

Tantalum/Silicon multilayers to be used as normal-incidence mirrors for 234A X-ray have been fabricated using plane magnetron sputtering system. The test and evaluation of characterizations have been given by Small Angle Diffraction with Cu-Ka radiation, Transmission Electron Microscopy and Auger Electron Spectrooscopy.
Simulation of Mixing at Mo/Si Interfaces
Authors: Boercker D. B. , Morgan W. L.
Published: February 2023

Soft x-ray projection lithography is a rapidly emerging technology which will have enormous impact on the microelectronics industry, by providing faithful image reduction to a minimum feature size below 1000Å.1 X-ray reduction cameras have already been designed and tested,2,3 but the successful development of this new technology will depend heavily upon the production of efficient, durable x-ray optics1.